Evidence supports active smoking as a major source of exposure to polycyclic aromatic hydrocarbons (PAH), compounds that are mutagenic and carcinogenic in humans. The influence of involuntary exposure to tobacco smoke on PAH exposure levels among nonsmokers, however, is unknown. This study evaluated the association between both active and involuntary tobacco smoke and biomarkers of PAH exposure in the general U.S. population. A cross-sectional analysis of 5,060 participants ≥6 years of age was done using data from the 1999-2002 National Health and Nutrition Examination Survey (NHANES). PAH exposure was measured by urinary concentrations of 23 monohydroxylated metabolites of nine PAH compounds. Tobacco smoke exposure was defined as no exposure, involuntary exposure, and active exposure by combining serum cotinine levels, smoking status, and presence of household smokers. PAH metabolite levels ranged from 33.9 ng/L for 9-hydroxyphenanthrene to 2,465.4 ng/L for 2-hydroxynaphthalene. After adjustment for age, sex, race/ethnicity, education, household income, and broiled/grilled food consumption, participants involuntarily and actively exposed to tobacco smoke had urinary metabolite concentrations that were increased by a factor of 1.1 to 1.4 and 1.5 to 6.9, respectively, compared with unexposed participants. Associations for involuntary smoking were stronger and statistically significant for 1-hydroxypyrene, 2-hydroxyfluorene, 3-hydroxyfluorene, 9-hydroxyfluorene, 1-hydroxyphenanthrene, 2-hydroxyphenanthrene, and 3-hydroxyphenanthrene compared with other metabolites. Involuntary exposure to tobacco smoke was associated with elevated urinary concentrations of most PAH metabolites in a representative sample of the U.S. population. Policy and educational efforts must continue to minimize PAH exposure through active and involuntary tobacco smoke exposure. (Cancer Epidemiol Biomarkers Prev 2009;18(3):884–93)

Polycyclic aromatic hydrocarbons (PAH), a group of more than 100 different compounds, are widely distributed in the environment as a result of incomplete combustion of natural and man-made organic materials (1, 2). Listed by the United States Environmental Protection Agency as priority environmental pollutants (3), many PAHs are established human carcinogens, mutagens, and cocarcinogens (1, 4-9). Major sources of nonoccupational exposure include tobacco smoke, contaminated foods, and polluted air and water (10-13).

Tobacco smoke, a major source of indoor air pollution, contains >60 known carcinogens, including PAHs, in both mainstream and sidestream fractions (14-16). Sufficient evidence has shown higher PAH exposure levels among current smokers compared with nonsmokers (17-20). Although the health effects among nonsmokers who live with or spend time in the proximity of smokers are well established (8), few studies have evaluated the contribution of involuntary tobacco smoke exposure (also known as secondhand smoke, passive smoke, or environmental tobacco smoke) to PAH levels (21, 22).

Our objective was to investigate the association between both active and involuntary tobacco smoke exposure with PAH as measured by urinary concentrations of monohydroxylated PAH metabolites in a representative sample of the civilian noninstitutionalized U.S. population using data from the National Health and Nutrition Examination Survey (NHANES) 1999-2002 (23, 24). Twenty-three metabolite isomers of the nine parent PAH compounds (benz[a]anthracene, benzo[a]pyrene, benzo[c]phenanthrene, chrysene, fluoranthene, fluorene, naphthalene, phenanthrene, and pyrene) were selected for study in NHANES 1999-2002 by the National Center for Health Statistics (NCHS). We hypothesized that the levels of tobacco smoke exposure are positively associated with urinary PAH metabolite concentrations in a dose-response manner in the general population.

Study Population

NHANES is a series of cross-sectional health and nutrition surveys designed to obtain data representing the civilian noninstitutionalized U.S. population. In 1999, NHANES began measuring urinary levels of monohydroxylated PAH metabolites in participants ≥6 y of age. Details of the survey design, data collection methods, and data files for NHANES are available from the NCHS Web site1

(23, 24). The NHANES protocol was reviewed and approved by the NCHS Institutional Review Board. All participants provided written informed consent at the time of household interview and physical examination.

NHANES 1999-2002 completed a total of 19,759 household interviews and standardized physical exams at a mobile examination center (response rate, 78%). One third of those ≥6 y of age were randomly selected for urinary monohydroxylated PAH metabolite measurements (n = 5,546), and over the period of 4 y, a total of 5,108 participants had 13 PAH metabolite measurements (23, 24). The analytic sample was reduced by about half for the 3-hydroxyfluoranthene (3-OHFrt) metabolite, which was only available in NHANES 1999-2000 (n = 2,457) and for the 3-hydroxybenzo[a]pyrene (3-OHB[a]P), 1-hydroxychrysene (1-OHChr), 2-hydroxychrysene (2-OHChr), 4-hydroxychrysene (4-OHChr), 9-hydroxyfluorene (9-OHFle), 4-hydroxyphenanthrene (4-OHPhe), 9-hydroxyphenanthrene (9-OHPhe), 1-hydroxynaphthalene (1-OHNap), and 2-hydroxynaphthalene (2-OHNap) metabolites, which were only available in NHANES 2001-2002 (n = 2,748). Additionally, sample sizes varied slightly for individual PAH metabolites due to missing levels for some metabolites (Table 1).

Table 1.

PAH metabolite concentrations (ng/L) in urine: NHANES 1999-2002

Metabolite (MW)Sample sizeGeometric meanMaximumLODPercent <LODRange of CV
Pyrene       
    1-OHPyr (218) 5,059 60.3 24,129 2,* 3.3 1.6 1.5-5.7 
Phenanthrene       
    1-OHPhe (194) 4,987 145.3 27,672 15,* 3.5 2.5 1.5-4.9 
    2-OHPhe (194) 4,921 69.3 26,249 11.2,* 3.2 6.6 1.4-6.7 
    3-OHPhe (194) 5,040 112.9 126,202 15.3,* 3.6 3.1 1.6-11.7 
    4-OHPhe (194) 2,741 41.9 7,323 5.7 25.5 1.0-3.9 
    9-OHPhe (194) 2,741 33.9 4,410 3.1 16.1 1.0-4.6 
Naphthalene       
    1-OHNap (144) 2,748 2,047.3 297,389 6.2 0.0 1.4-4.3 
    2-OHNap (144) 2,748 2,465.4 223,087 2.4 0.0 0.9-3.5 
Fluorene       
    2-OHFle (182) 5,060 363.0 85,466 9.5,* 3.6 0.9 1.4-5.4 
    3-OHFle (182) 5,057 146.4 29,328 15.1,* 2 4.3 1.5-3.7 
    9-OHFle (182) 2,745 218.9 67,885 2.8 0.9 0.9-5.9 
Fluoranthene       
    3-OHFrt (218) 2,236 13.4 5,490 3.5* 29.4 1.2-5.9 
Benzo[a]pyrene       
    3-OHB[a]P (270) 2,748 17.5 12,519 10.5 50.5 2.4-7.9 
Benz[a]anthracene       
    1-OHB[a]A (244) 4,832 3.5 1,014 4.7,* 3.9 93.1 1.9-7.0 
    3-OHB[a]A (244) 4,900 6.3 312 5.4,* 10.4 86.0 0.5-2.1 
Benzo[c]phenanthrene       
    1-OHB[c]P (244) 4,932 4.0 5,067 5.7,* 3.4 78.8 1.9-10.9 
    2-OHB[c]P (244) 4,923 4.9 4,107 6.8,* 5.4 86.3 0.9-12.5 
    3-OHB[c]P (244) 4,920 3.8 447 4.9,* 5.4 93.3 0.7-4.3 
Chrysene       
    1-OHChr (244) 2,748 7.1 992 5 71.8 1.8-3.1 
    2-OHChr (244) 2,748 4.4 460 5 87.9 1.4-3.1 
    3-OHChr (244) 4,981 7.8 2,326 9.9,* 8.3 84.6 1.0-7.7 
    4-OHChr (244) 2,748 2.3 314 2.8 95.4 0.7-4.7 
    6-OHChr (244) 5,015 3.0 868 3.4,* 2.4 78.5 2.5-4.6 
Metabolite (MW)Sample sizeGeometric meanMaximumLODPercent <LODRange of CV
Pyrene       
    1-OHPyr (218) 5,059 60.3 24,129 2,* 3.3 1.6 1.5-5.7 
Phenanthrene       
    1-OHPhe (194) 4,987 145.3 27,672 15,* 3.5 2.5 1.5-4.9 
    2-OHPhe (194) 4,921 69.3 26,249 11.2,* 3.2 6.6 1.4-6.7 
    3-OHPhe (194) 5,040 112.9 126,202 15.3,* 3.6 3.1 1.6-11.7 
    4-OHPhe (194) 2,741 41.9 7,323 5.7 25.5 1.0-3.9 
    9-OHPhe (194) 2,741 33.9 4,410 3.1 16.1 1.0-4.6 
Naphthalene       
    1-OHNap (144) 2,748 2,047.3 297,389 6.2 0.0 1.4-4.3 
    2-OHNap (144) 2,748 2,465.4 223,087 2.4 0.0 0.9-3.5 
Fluorene       
    2-OHFle (182) 5,060 363.0 85,466 9.5,* 3.6 0.9 1.4-5.4 
    3-OHFle (182) 5,057 146.4 29,328 15.1,* 2 4.3 1.5-3.7 
    9-OHFle (182) 2,745 218.9 67,885 2.8 0.9 0.9-5.9 
Fluoranthene       
    3-OHFrt (218) 2,236 13.4 5,490 3.5* 29.4 1.2-5.9 
Benzo[a]pyrene       
    3-OHB[a]P (270) 2,748 17.5 12,519 10.5 50.5 2.4-7.9 
Benz[a]anthracene       
    1-OHB[a]A (244) 4,832 3.5 1,014 4.7,* 3.9 93.1 1.9-7.0 
    3-OHB[a]A (244) 4,900 6.3 312 5.4,* 10.4 86.0 0.5-2.1 
Benzo[c]phenanthrene       
    1-OHB[c]P (244) 4,932 4.0 5,067 5.7,* 3.4 78.8 1.9-10.9 
    2-OHB[c]P (244) 4,923 4.9 4,107 6.8,* 5.4 86.3 0.9-12.5 
    3-OHB[c]P (244) 4,920 3.8 447 4.9,* 5.4 93.3 0.7-4.3 
Chrysene       
    1-OHChr (244) 2,748 7.1 992 5 71.8 1.8-3.1 
    2-OHChr (244) 2,748 4.4 460 5 87.9 1.4-3.1 
    3-OHChr (244) 4,981 7.8 2,326 9.9,* 8.3 84.6 1.0-7.7 
    4-OHChr (244) 2,748 2.3 314 2.8 95.4 0.7-4.7 
    6-OHChr (244) 5,015 3.0 868 3.4,* 2.4 78.5 2.5-4.6 

Abbreviations: MW, molecular weight; CV, coefficient of variation.

*

Data are from NHANES 1999-2000.

Data are from NHANES 2001-2002.

Proportion of results below the LOD was >20% of population.

Urinary Monohydroxylated PAH Metabolites

A 5-mL aliquot from each spot urine specimen was taken for PAH metabolite measurements. The following 23 monohydroxylated metabolites were measured at the Division of Environmental Health Laboratory Sciences of the Centers for Disease Control and Prevention: 1-hydroxybenz[a]anthracene (1-OHB[a]A), 3-hydroxybenz[a]anthracene (3-OHB[a]A), 3-OHB[a]P, 1-hydroxybenzo[c]phenanthrene (1-OHB[c]P), 2-hydroxybenzo[c]phenanthrene (2-OHB[c]P), 3-hydroxybenzo[c]phenanthrene (3-OHB[c]P), 1-OHChr, 2-OHChr, 3-hydroxychrysene (3-OHChr), 4-OHChr, 6-hydroxychrysene (6-OHChr), 3-OHFrt, 2-hydroxyfluorene (2-OHFle), 3-hydroxyfluorene (3-OHFle), 9-OHFle, 1-OHNap, 2-OHNap, 1-hydroxyphenanthrene (1-OHPhe), 2-hydroxyphenanthrene (2-OHPhe), 3-hydroxyphenanthrene (3-OHPhe), 4-OHPhe, 9-OHPhe, and 1-hydroxypyrene (1-OHPyr; refs. 23, 24).

The analytic procedure for measurement of monohydroxylated metabolites of PAH involved enzymatic hydrolysis of urine, solid-phase extraction, derivatization, and analysis using capillary gas chromatography combined with high-resolution mass spectrometry following previously described methods (25, 26). Isotope dilution with 13C-labeled standards was used for quantification. Blanks, urine pools, and internal standard samples were used in each analytic run for quality control purposes. The ranges for the interassay coefficients of variation for each metabolite are shown in Table 1. The limits of detection (LOD) varied by metabolite and survey years, ranging from 2 ng/L for 1-OHPyr to 15.3 ng/L for 3-OHPhe (Table 1). The NCHS imputed a default value of LOD divided by the square root of two for those subjects with metabolite levels below the LOD. Metabolites for which >20% of participants were below the LOD were not considered further for this study.

Smoking Status and Tobacco Smoke Exposure

Participants ≥20 y of age were classified as never, former, or current smokers based on the household interview items: “Have you smoked at least 100 cigarettes in your entire life?” and “Do you now smoke cigarettes?” Smoking status among participants 12 to 19 y of age was derived from audio-computer-assisted interview items: “Have you ever tried cigarette smoking, even 1 or 2 puffs?” and “During the past 30 days, on how many days did you smoke cigarettes?”

Serum cotinine, a metabolite of nicotine, was determined using isotope dilution high-performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry (23, 24). The LOD for serum cotinine was <0.05 ng/mL.

Similar to Weitzman et al. (27), we defined current active smoking exposure, involuntary smoking exposure, and no exposure to tobacco smoke by combining cotinine levels, living with a smoker in the household, and smoking status as follows: (a) active smoking exposure was defined as self-reported current smoking or cotinine levels ≥10 ng/mL (28); (b) involuntary exposure to tobacco smoke was defined as parental report of any smoker in the home or detectable but <10 ng/mL cotinine levels in children <12 y of age (28, 29), and as self-report of any smoker living in the home in the absence of self-reported smoking or detectable but <10 ng/mL cotinine levels in adolescents and adults; and (c) no exposure to tobacco smoke was defined as cotinine levels below the LOD, not living with a smoker, and not being a current smoker. Three children ages 6 to 11 y with cotinine levels ≥10 ng/mL were dropped from our analyses; thus, no active smoking exposure category existed for this age group.

Other Variables

Potential determinants of PAH metabolites evaluated in our analyses included age, sex, race/ethnicity, education, poverty income ratio (PIR), consumption of grilled/broiled meat and alcohol, body mass index (BMI), current occupation, physical activity level, and urinary creatinine. Age, sex, race/ethnicity, education, current occupation, physical activity, and alcohol consumption were obtained during the interview based on self-reported information. PIR is a ratio of self-reported family income to the family's poverty threshold values, which were standardized by family size and inflation rates based on tables published annually by the U.S. Bureau of Census (30). Self-reported grilled/broiled meat intake was obtained from the dietary interview component of NHANES and recoded as “yes” or “no” according to whether participants reported having eaten any grilled or broiled red meat in the past 24 h. Data on description of food and cooking method consumed by each participant were obtained from the U.S. Department of Agriculture food and nutrition database (31). Alcohol consumption in adults was classified as never, former, and current. The level of physical activity was computed from the total metabolic equivalent of task scores for all physical activities done in the previous 30 d.

BMI (kg/m2) in adults was computed from measured weight and height and categorized into normal (BMI, <25 kg/m2), overweight (BMI, 25-29 kg/m2), and obese (BMI, ≥30 kg/m2). BMI in children and adolescents (<20 y old) was based on the age- and sex-specific BMI growth charts (32) as normal (BMI, <85th percentile), at risk for overweight (BMI, 85-95th percentile), and overweight (BMI, ≥95th percentile; ref. 33). Urinary creatinine was measured in the same specimen as PAH metabolites by using a photometric Boehringer Mannheim/Hitachi 912 analyzer (23, 24).

Statistical Analysis

All statistical analyses were conducted with STATA version 9.2 statistical software (Stata Corp.) using appropriate sampling weights developed by NCHS for this random subsample to obtain accurate estimates representative of the noninstitutionalized U.S. population (34). The Taylor linearization method was used to obtain proper SEs of all estimates.

PAH metabolites were right skewed and log10 transformed for the analyses. Geometric means and interquartile ranges were computed for all metabolites. To assess determinants of PAH exposure, the ratios and 95% confidence intervals (95% CI) of the geometric mean PAH metabolite levels were estimated using linear regression models on log10-transformed metabolite levels by main determinants including age, sex, race/ethnicity, education, PIR, self-reported dietary grilled/broiled meat, cotinine levels, smoking status (never/former/current), and current exposure to tobacco smoke (none/involuntary/active).

To examine the association of each metabolite with current exposure to tobacco smoke, linear regression models on log10-transformed PAH metabolite levels were first adjusted for age, sex, race/ethnicity, education level, and PIR. We then further adjusted for self-reported dietary grilled/broiled meat, a known source of PAH exposure (2). Because urinary PAH metabolites were measured in a spot urine sample, and thus influenced by factors such as fluid intake, perspiration, and glomerular filtration rate (35), we added urinary creatinine to each final model to adjust for individual differences in urine concentration (36). We also assessed other potential confounding by current occupation, BMI, alcohol use, and levels of physical activity by adding them one at a time to multivariable models. No noticeable changes were observed (data not shown) and these additional variables were not included in our final models.

PAH Metabolite Concentrations in Urine

The overall geometric means and LOD of 23 monohydroxylated metabolites of nine parent PAH compounds in this sample of the U.S. population ≥6 years of age are presented in Table 1. PAH levels varied widely by metabolite, with geometric means ranging from 2.3 ng/L for 4-OHChr to 2,465.4 ng/L for 2-OHNap. For metabolites of phenanthrene (4-OHPhe), fluoranthene (3-OHFrt), benzo[a]pyrene (3-OHB[a]P), benz[a]anthracene (1-OHB[a]A and 3-OHB[a]A), benzo[c]phenanthrene (1-OHB[c]P, 2-OHB[c]P, and 3-OHB[c]P), and chrysene (1-OHChr, 2-OHChr, 3-OHChr, 4-OHChr, and 6-OHChr), the levels were below the LOD in >20% of the population. Therefore, these metabolites were not considered in further analyses. For the other 10 PAH metabolites, the proportion of detectable values ranged from 83.9% for 9-OHPhe to 100% for 2-OHNap.

Sociodemographic Determinants of Urinary PAH Concentrations

Men had higher levels for all metabolites (Fig. 1). Urinary PAH concentrations for almost all metabolites varied somewhat by age, with the highest geometric means found in persons 20 to 39 years old. By race/ethnicity, non-Hispanic Black participants had higher levels of PAH exposure than non-Hispanic White and Mexican American participants for most metabolites. The geometric means of most PAH metabolites were lower in participants with higher education level and with higher PIRs (higher adjusted income).

Figure 1.

PAH metabolite concentrations in urine (ng/L) by participant characteristics in the 1999-2002 NHANES sample.

Figure 1.

PAH metabolite concentrations in urine (ng/L) by participant characteristics in the 1999-2002 NHANES sample.

Close modal

After multivariable adjustment, urinary concentrations of most PAH metabolites were comparable in men and women, although 1-OHPhe and 2-OHNap concentrations were significantly higher in women (Table 2). The adjusted ratios of geometric means for most metabolites were lower in participants 12 to 39 years of age with respect to the youngest age group (6-11 years of age) for most metabolites, except 2-OHPhe. Except for 1-OHNap, 3-OHFle, 1-OHPhe, 3-OHPhe, and 9-OHPhe, which were significantly lower in Mexican Americans, and 1-OHPhe and 9-OHPhe, which were lower in non-Hispanic Blacks compared with non-Hispanic Whites, no major racial/ethnic differences were observed. Inverse associations between income (as measured by PIR) and education levels with PAH metabolite concentrations remained present for most isomers.

Table 2.

Ratio (95% CI) of the geometric means of PAH metabolite concentrations in urine in the U.S. population: NHANES 1999-2002

Characteristics%*1-OHPyr1-OHPhe2-OHPhe3-OHPhe9-OHPhe
Sex       
    Male 48 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Female 52 1.00 (0.91-1.10) 1.17 (1.09-1.25) 1.03 (0.94-1.13) 0.99 (0.92-1.06) 1.08 (0.97-1.20) 
Age group (y)       
    6-11 10 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    12-19 13 0.61 (0.55-0.68) 0.85 (0.74-0.99) 0.85 (0.71-1.03) 0.67 (0.59-0.75) 0.57 (0.47-0.68) 
    20-39 31 0.65 (0.58-0.72) 0.93 (0.84-1.03) 1.10 (0.97-1.24) 0.71 (0.63-0.81) 0.68 (0.58-0.81) 
    40-59 29 0.67 (0.58-0.77) 1.13 (1.00-1.28) 1.27 (1.08-1.48)§ 0.79 (0.69-0.89) 0.94 (0.76-1.17) 
    ≥60 17 0.55 (0.49-0.62) 1.12 (0.99-1.28) 1.22 (1.06-1.40)§ 0.82 (0.69-0.97) 0.94 (0.74-1.19) 
Race/ethnicity       
    White 69 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Black 11 0.87 (0.74-1.02) 0.73 (0.60-0.89)§ 0.84 (0.68-1.04) 0.95 (0.79-1.14) 0.65 (0.55-0.77) 
    Mexican American 0.96 (0.82-1.13) 0.78 (0.65-0.92)§ 0.85 (0.68-1.05) 0.82 (0.71-0.95) 0.78 (0.68-0.89)§ 
    Other 11 1.06 (0.88-1.28) 0.85 (0.65-1.12) 0.88 (0.64-1.22) 0.82 (0.65-1.02) 0.85 (0.64-1.14) 
Education       
    <High school 37 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    High school 21 0.95 (0.84-1.06) 1.08 (0.96-1.22) 1.02 (0.90-1.16) 0.98 (0.87-1.11) 0.87 (0.72-1.05) 
    >High school 42 0.84 (0.75-0.93)§ 0.91 (0.80-1.03) 0.83 (0.71-0.97) 0.90 (0.81-1.01) 0.99 (0.81-1.22) 
PIR       
    Low (0 to <1.7) 32 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Medium (1.7 to <3.9) 33 0.86 (0.75-0.98) 0.90 (0.78-1.04) 0.83 (0.72-0.97) 0.93 (0.81-1.06) 0.98 (0.86-1.11) 
    High (3.9 to 5) 35 0.82 (0.69-0.96) 0.86 (0.73-1.00) 0.75 (0.64-0.87) 0.84 (0.73-0.97) 0.92 (0.76-1.12) 
Grilled/broiled meat eaten       
    No 93 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Yes 1.19 (0.97-1.45) 1.13 (0.94-1.37) 1.09 (0.90-1.32) 1.25 (1.06-1.48) 1.18 (1.06-1.33)§ 
Tobacco smoke exposure       
    Unexposed 39 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Involuntary 34 1.43 (1.27-1.62) 1.25 (1.09-1.42)§ 1.40 (1.17-1.67) 1.30 (1.17-1.46) 1.09 (0.95-1.24) 
    Active
 
27
 
2.86 (2.45-3.35)
 
1.51 (1.32-1.73)
 
1.80 (1.49-2.17)
 
2.08 (1.77-2.44)
 
3.25 (2.81-3.76)
 
Characteristics
 
1-OHNap
 
2-OHNap
 
2-OHFle
 
3-OHFle
 
9-OHFle
 
Sex      
    Male 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Female 1.06 (0.99-1.14) 1.16 (1.04-1.28) 1.05 (0.98-1.12) 1.01 (0.94-1.09) 0.99 (0.90-1.09) 
Age group (y)      
    6-11 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    12-19 0.66 (0.55-0.80) 0.66 (0.56-0.79) 0.72 (0.62-0.83) 0.69 (0.61-0.79) 0.73 (0.64-0.84) 
    20-39 0.76 (0.61-0.93) 0.86 (0.75-0.99) 0.86 (0.75-0.98) 0.79 (0.70-0.90) 0.86 (0.70-1.05) 
    40-59 0.98 (0.73-1.32) 1.09 (0.97-1.23) 1.07 (0.95-1.21) 0.96 (0.84-1.10) 1.14 (0.90-1.44) 
    ≥60 1.39 (1.05-1.85) 0.92 (0.78-1.10) 0.98 (0.85-1.13) 0.81 (0.71-0.92)§ 1.22 (1.00-1.49) 
Race/ethnicity      
    White 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Black 0.97 (0.75-1.25) 1.13 (0.96-1.32) 0.94 (0.71-1.24) 1.00 (0.78-1.28) 1.07 (0.93-1.22) 
    Mexican American 0.85 (0.72-0.99) 1.14 (0.96-1.35) 0.78 (0.61-1.00) 0.73 (0.58-0.92) 0.93 (0.75-1.16) 
    Other 0.88 (0.71-1.08) 1.25 (0.95-1.64) 0.93 (0.67-1.29) 0.97 (0.74-1.27) 0.79 (0.59-1.06) 
Education      
    <High school 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    High school 1.00 (0.76-1.31) 0.96 (0.86-1.06) 1.07 (0.91-1.25) 1.11 (0.95-1.29) 0.98 (0.83-1.15)  
    >High school 0.92 (0.81-1.06) 0.94 (0.80-1.12) 0.84 (0.74-0.95) 0.84 (0.74-0.96) 1.01 (0.82-1.23) 
PIR      
    Low (0 to <1.7) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Medium (1.7 to <3.9) 0.85 (0.75-0.96) 0.82 (0.76-0.89) 0.85 (0.74-0.97) 0.85 (0.74-0.97) 0.94 (0.84-1.05) 
    High (3.9-5) 0.85 (0.72-0.99) 0.72 (0.67-0.78) 0.75 (0.65-0.86) 0.77 (0.68-0.87) 0.83 (0.69-1.00) 
Grilled/broiled meat eaten      
    No 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Yes 1.33 (1.12-1.58)§ 1.37 (1.12-1.68)§ 1.16 (0.96-1.40) 1.21 (0.99-1.47) 1.15 (0.96-1.38) 
Tobacco smoke exposure      
    Unexposed 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Involuntary 1.12 (0.96-1.30) 1.17 (0.98-1.40) 1.38 (1.16-1.65) 1.36 (1.16-1.60) 1.38 (1.17-1.63)§ 
    Active 3.94 (3.53-4.38) 4.50 (3.83-5.28) 4.57 (3.84-5.43) 6.87 (5.83-8.09) 1.92 (1.62-2.29) 
Characteristics%*1-OHPyr1-OHPhe2-OHPhe3-OHPhe9-OHPhe
Sex       
    Male 48 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Female 52 1.00 (0.91-1.10) 1.17 (1.09-1.25) 1.03 (0.94-1.13) 0.99 (0.92-1.06) 1.08 (0.97-1.20) 
Age group (y)       
    6-11 10 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    12-19 13 0.61 (0.55-0.68) 0.85 (0.74-0.99) 0.85 (0.71-1.03) 0.67 (0.59-0.75) 0.57 (0.47-0.68) 
    20-39 31 0.65 (0.58-0.72) 0.93 (0.84-1.03) 1.10 (0.97-1.24) 0.71 (0.63-0.81) 0.68 (0.58-0.81) 
    40-59 29 0.67 (0.58-0.77) 1.13 (1.00-1.28) 1.27 (1.08-1.48)§ 0.79 (0.69-0.89) 0.94 (0.76-1.17) 
    ≥60 17 0.55 (0.49-0.62) 1.12 (0.99-1.28) 1.22 (1.06-1.40)§ 0.82 (0.69-0.97) 0.94 (0.74-1.19) 
Race/ethnicity       
    White 69 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Black 11 0.87 (0.74-1.02) 0.73 (0.60-0.89)§ 0.84 (0.68-1.04) 0.95 (0.79-1.14) 0.65 (0.55-0.77) 
    Mexican American 0.96 (0.82-1.13) 0.78 (0.65-0.92)§ 0.85 (0.68-1.05) 0.82 (0.71-0.95) 0.78 (0.68-0.89)§ 
    Other 11 1.06 (0.88-1.28) 0.85 (0.65-1.12) 0.88 (0.64-1.22) 0.82 (0.65-1.02) 0.85 (0.64-1.14) 
Education       
    <High school 37 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    High school 21 0.95 (0.84-1.06) 1.08 (0.96-1.22) 1.02 (0.90-1.16) 0.98 (0.87-1.11) 0.87 (0.72-1.05) 
    >High school 42 0.84 (0.75-0.93)§ 0.91 (0.80-1.03) 0.83 (0.71-0.97) 0.90 (0.81-1.01) 0.99 (0.81-1.22) 
PIR       
    Low (0 to <1.7) 32 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Medium (1.7 to <3.9) 33 0.86 (0.75-0.98) 0.90 (0.78-1.04) 0.83 (0.72-0.97) 0.93 (0.81-1.06) 0.98 (0.86-1.11) 
    High (3.9 to 5) 35 0.82 (0.69-0.96) 0.86 (0.73-1.00) 0.75 (0.64-0.87) 0.84 (0.73-0.97) 0.92 (0.76-1.12) 
Grilled/broiled meat eaten       
    No 93 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Yes 1.19 (0.97-1.45) 1.13 (0.94-1.37) 1.09 (0.90-1.32) 1.25 (1.06-1.48) 1.18 (1.06-1.33)§ 
Tobacco smoke exposure       
    Unexposed 39 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Involuntary 34 1.43 (1.27-1.62) 1.25 (1.09-1.42)§ 1.40 (1.17-1.67) 1.30 (1.17-1.46) 1.09 (0.95-1.24) 
    Active
 
27
 
2.86 (2.45-3.35)
 
1.51 (1.32-1.73)
 
1.80 (1.49-2.17)
 
2.08 (1.77-2.44)
 
3.25 (2.81-3.76)
 
Characteristics
 
1-OHNap
 
2-OHNap
 
2-OHFle
 
3-OHFle
 
9-OHFle
 
Sex      
    Male 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Female 1.06 (0.99-1.14) 1.16 (1.04-1.28) 1.05 (0.98-1.12) 1.01 (0.94-1.09) 0.99 (0.90-1.09) 
Age group (y)      
    6-11 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    12-19 0.66 (0.55-0.80) 0.66 (0.56-0.79) 0.72 (0.62-0.83) 0.69 (0.61-0.79) 0.73 (0.64-0.84) 
    20-39 0.76 (0.61-0.93) 0.86 (0.75-0.99) 0.86 (0.75-0.98) 0.79 (0.70-0.90) 0.86 (0.70-1.05) 
    40-59 0.98 (0.73-1.32) 1.09 (0.97-1.23) 1.07 (0.95-1.21) 0.96 (0.84-1.10) 1.14 (0.90-1.44) 
    ≥60 1.39 (1.05-1.85) 0.92 (0.78-1.10) 0.98 (0.85-1.13) 0.81 (0.71-0.92)§ 1.22 (1.00-1.49) 
Race/ethnicity      
    White 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Black 0.97 (0.75-1.25) 1.13 (0.96-1.32) 0.94 (0.71-1.24) 1.00 (0.78-1.28) 1.07 (0.93-1.22) 
    Mexican American 0.85 (0.72-0.99) 1.14 (0.96-1.35) 0.78 (0.61-1.00) 0.73 (0.58-0.92) 0.93 (0.75-1.16) 
    Other 0.88 (0.71-1.08) 1.25 (0.95-1.64) 0.93 (0.67-1.29) 0.97 (0.74-1.27) 0.79 (0.59-1.06) 
Education      
    <High school 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    High school 1.00 (0.76-1.31) 0.96 (0.86-1.06) 1.07 (0.91-1.25) 1.11 (0.95-1.29) 0.98 (0.83-1.15)  
    >High school 0.92 (0.81-1.06) 0.94 (0.80-1.12) 0.84 (0.74-0.95) 0.84 (0.74-0.96) 1.01 (0.82-1.23) 
PIR      
    Low (0 to <1.7) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Medium (1.7 to <3.9) 0.85 (0.75-0.96) 0.82 (0.76-0.89) 0.85 (0.74-0.97) 0.85 (0.74-0.97) 0.94 (0.84-1.05) 
    High (3.9-5) 0.85 (0.72-0.99) 0.72 (0.67-0.78) 0.75 (0.65-0.86) 0.77 (0.68-0.87) 0.83 (0.69-1.00) 
Grilled/broiled meat eaten      
    No 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Yes 1.33 (1.12-1.58)§ 1.37 (1.12-1.68)§ 1.16 (0.96-1.40) 1.21 (0.99-1.47) 1.15 (0.96-1.38) 
Tobacco smoke exposure      
    Unexposed 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 1.00 (reference) 
    Involuntary 1.12 (0.96-1.30) 1.17 (0.98-1.40) 1.38 (1.16-1.65) 1.36 (1.16-1.60) 1.38 (1.17-1.63)§ 
    Active 3.94 (3.53-4.38) 4.50 (3.83-5.28) 4.57 (3.84-5.43) 6.87 (5.83-8.09) 1.92 (1.62-2.29) 

NOTE: Final model was adjusted by age, sex, race/ethnicity, education, PIR, tobacco smoke exposure, self-reported dietary grilled/broiled meat, and urinary creatinine. The model was fit based on linear regression with complex survey design weight using log10-transformed urinary PAH metabolite concentrations. Ratios were reported as detransformed β.

*

Weighted percentage.

P ≤ 0.001.

P ≤ 0.05.

§

P ≤ 0.01.

Unexposed defined as not being a current smoker, having cotinine level <0.05 ng/mL, and no report of living with any smoker in the home; involuntary defined as not being a current smoker, having cotinine level 0.05 to <10 ng/mL, or report of living with any smoker in the home; active defined as being a current smoker or having cotinine level ≥10 ng/mL.

Grilled/Broiled Meat and Urinary PAH Concentrations

After multivariable adjustment, self-reported grilled/broiled meat consumption was associated with increased concentrations of most PAH metabolites (Table 2). For 3-OHPhe, 9-OHPhe, 1-OHNap, and 2-OHNap, the adjusted ratios of the geometric means were statistically significant and increased by 18% to 37% compared with participants who did not report eating grilled/broiled meat.

Exposure to Tobacco Smoke and Urinary PAH Concentrations

Current smokers had higher urinary PAH metabolite concentrations compared with nonsmokers for all metabolites (Fig. 1), but no substantial differences were observed between nonsmokers and former smokers. Urinary concentrations of PAH metabolites also increased with increasing serum cotinine levels. Levels of all isomers were highest in the active tobacco smoke exposure group and lowest in participants not exposed to tobacco smoke. Participants involuntarily exposed to tobacco smoke had intermediate concentrations (Fig. 1).

After multivariable adjustment, tobacco smoke exposure status remained strongly associated with urinary concentrations of most isomers, showing a dose-response trend (Table 2). For example, the ratios of geometric means for 1-OHPyr in participants involuntarily and actively exposed to tobacco smoke were 1.43-fold (95% CI, 1.27-1.62) and 2.86-fold (95% CI, 2.45-3.35) greater, respectively, compared with the unexposed group. Ratios were similar for other isomers (Table 2; Fig. 1). Adjusted R2 of full models accounted for 24% to 53% of the observed variability of most PAH metabolite concentrations. The addition of tobacco smoke exposure status to the final models explained approximately 3% to 24% of the outcome variability, supporting the hypothesis that tobacco smoke exposure was an important predictor of PAH metabolite concentrations in urine.

Exposure to Tobacco Smoke and Urinary PAH Concentrations by Sociodemographic Characteristics

Increasing levels of exposure to tobacco smoke remained consistently and strongly associated with increased urine 1-OHPyr concentrations among children >6 years, adolescents, and adults (Table 3). For most subgroups, the adjusted ratios of geometric means of 1-OHPyr among participants involuntarily exposed to tobacco smoke were ∼1.5 times higher compared with unexposed groups. The corresponding adjusted ratios for active smokers compared with unexposed were 2.4 to 3 times higher. Similar patterns were observed in subgroups defined by sex, race/ethnicity, education, poverty level, and self-reported dietary grilled/broiled meat. Similar findings by sociodemographic characteristics were observed for the association of tobacco smoke with other PAH metabolites (data not shown).

Table 3.

Ratio of geometric means (95% CI) of 1-OHPyrFS concentration in urine (ng/L) related to tobacco smoke exposure status by participant characteristics, NHANES 1999-2002

Tobacco smoke exposure status
Unexposed*InvoluntaryActive
Age group (y)    
    Children (6-11) 1.00 (reference) 1.58 (1.25-1.99) N/A 
    Adolescents (12-19) 1.00 (reference) 1.56 (1.18-2.08) 2.35 (1.95-2.83) 
    Adults (20-85) 1.00 (reference) 1.38 (1.19-1.60) 2.95 (2.46-3.54) 
Sex    
    Male 1.00 (reference) 1.51 (1.26-1.80) 2.73 (2.32-3.22) 
    Female 1.00 (reference) 1.35 (1.18-1.55) 2.83 (2.30-3.49) 
Race/ethnicity    
    White 1.00 (reference) 1.50 (1.28-1.75) 2.98 (2.41-3.68) 
    Black 1.00 (reference) 1.20 (0.90-1.62) 2.69 (1.87-3.86) 
    Mexican American 1.00 (reference) 1.42 (1.17-1.73) 1.95 (1.57-2.42) 
    Other 1.00 (reference) 1.25 (0.91-1.70) 2.04 (1.49-2.80) 
Education level    
    <High school 1.00 (reference) 1.47 (1.30-1.65) 2.79 (2.44-3.18) 
    High school 1.00 (reference) 1.44 (1.16-1.78) 3.15 (2.34-4.25) 
    >High school 1.00 (reference) 1.45 (1.19-1.78) 2.67 (2.16-3.31) 
Poverty level (PIR)    
    Low 1.00 (reference) 1.38 (1.11-1.72) 2.99 (2.35-3.81) 
    Medium 1.00 (reference) 1.47 (1.19-1.81) 2.80 (2.21-3.52) 
    High 1.00 (reference) 1.47 (1.24-1.74) 2.41 (2.03-2.87) 
Grilled/broiled meat    
    No 1.00 (reference) 1.46 (1.29-1.66) 2.83 (2.39-3.35) 
    Yes 1.00 (reference) 1.10 (0.82-1.48) 2.16 (1.47-3.18) 
Tobacco smoke exposure status
Unexposed*InvoluntaryActive
Age group (y)    
    Children (6-11) 1.00 (reference) 1.58 (1.25-1.99) N/A 
    Adolescents (12-19) 1.00 (reference) 1.56 (1.18-2.08) 2.35 (1.95-2.83) 
    Adults (20-85) 1.00 (reference) 1.38 (1.19-1.60) 2.95 (2.46-3.54) 
Sex    
    Male 1.00 (reference) 1.51 (1.26-1.80) 2.73 (2.32-3.22) 
    Female 1.00 (reference) 1.35 (1.18-1.55) 2.83 (2.30-3.49) 
Race/ethnicity    
    White 1.00 (reference) 1.50 (1.28-1.75) 2.98 (2.41-3.68) 
    Black 1.00 (reference) 1.20 (0.90-1.62) 2.69 (1.87-3.86) 
    Mexican American 1.00 (reference) 1.42 (1.17-1.73) 1.95 (1.57-2.42) 
    Other 1.00 (reference) 1.25 (0.91-1.70) 2.04 (1.49-2.80) 
Education level    
    <High school 1.00 (reference) 1.47 (1.30-1.65) 2.79 (2.44-3.18) 
    High school 1.00 (reference) 1.44 (1.16-1.78) 3.15 (2.34-4.25) 
    >High school 1.00 (reference) 1.45 (1.19-1.78) 2.67 (2.16-3.31) 
Poverty level (PIR)    
    Low 1.00 (reference) 1.38 (1.11-1.72) 2.99 (2.35-3.81) 
    Medium 1.00 (reference) 1.47 (1.19-1.81) 2.80 (2.21-3.52) 
    High 1.00 (reference) 1.47 (1.24-1.74) 2.41 (2.03-2.87) 
Grilled/broiled meat    
    No 1.00 (reference) 1.46 (1.29-1.66) 2.83 (2.39-3.35) 
    Yes 1.00 (reference) 1.10 (0.82-1.48) 2.16 (1.47-3.18) 

NOTE: Model was adjusted by age, sex, race/ethnicity, education, PIR, self-reported dietary grilled/broiled meat, and urinary creatinine. The model was fit based on linear regression with complex survey design weighting using log10-transformed urinary PAH metabolite concentrations. Ratios were reported as detransformed β. A ratio of 1.58, for instance, indicates a 58% increased level with respect to the reference category.

*

Unexposed defined as not being a current smoker, having cotinine level <0.05 ng/mL, and no report of living with any smoker in the home.

Involuntary defined as not being a current smoker, having cotinine level 0.05 to <10 ng/mL, or report of living with any smoker in the home.

Active defined as being a current smoker or having cotinine level ≥10 ng/mL.

Summary of Findings

In a representative sample of the U.S. population, children and adults involuntarily and actively exposed to tobacco smoke had higher concentrations of PAH metabolites in urine compared with those not exposed. The association persisted after adjustment for other determinants of PAH exposure, including age, sex, race/ethnicity, education, income, and broiled/grilled meat consumption. A consistent dose-response relationship was observed between recent levels of tobacco smoke exposure (active/involuntary/unexposed) and by cotinine levels with almost every metabolite. No differences in PAH levels were observed between never and former smokers, supporting the view that urinary PAH metabolites reflect recent and ongoing exposure to tobacco smoke, including involuntary exposure, but not past or cumulative exposure.

PAH Exposure—Comparison with Other Countries

Urinary monohydroxylated PAH metabolite concentrations obtained in our study were similar to those previously reported for the 1999-2000 NHANES population (37) but generally lower than concentrations in selected nonoccupationally exposed populations in Canada (38), Germany (39), Sweden (40), and the Netherlands (11). Urinary PAH concentrations in this U.S. sample were also much lower than in populations in China, where the average ambient air levels of PAH in urban areas are much higher (116 ng/m3; ref. 41) compared with average PAH levels in ambient air in urban and rural areas of the United States (0.15-19.3 ng/m3 and 0.02-1.2 ng/m3, respectively; refs. 42, 43).

Differences in target populations and in the methodology used in different studies, including differences in analytic techniques, make comparisons across studies difficult (37). Whereas most studies have measured PAHs in selective occupationally exposed individuals or in individuals living in areas with significant environmental sources of PAH, NHANES is a nationally representative sample of the U.S. general population. In the United States, levels of PAH concentrations in the ambient air are generally low and food and tobacco smoke are likely to be the most significant sources of PAH exposure. Given important recent reductions in active smoking (44) and in involuntary exposure to tobacco smoke at home and in public places in the United States (45), it is possible that lower PAH metabolite concentrations in the U.S. population also reflect lower exposure to tobacco smoke compared with other countries. Because this was the first time that PAH metabolites were measured in the general U.S. population, however, it is not possible to compare our findings with previous times.

Tobacco Smoke Exposure

Urinary excretion of PAH metabolites was increased in participants with involuntary and active tobacco smoke exposure by a factor of 1.1 to 1.4 and 1.5 to 6.9, respectively, compared with unexposed participants. The contribution of active cigarette smoking to PAH exposure is well established. Multiple studies have consistently reported 1-OHPyr concentrations in urine to be 1.5 to 3 times higher among current smokers compared with nonsmokers (18, 20, 39, 46, 47). Although less frequently studied, similar trends have been observed for other monohydroxylated PAH metabolites, such as 2-OHFle (48), 1-OHPhe, 2-OHPhe, 3-OHPhe, 4-OHPhe, and 9-OHPhe (39, 49), 3-OHB[a]P (20), and 1-OHNap and 2-OHNap (48, 50).

A limited number of studies have evaluated the effect of involuntary tobacco smoke exposure on PAH biomarkers (11, 22, 49, 50), with some detecting a positive association with urinary 1-OHPyr (52, 53) and with PAH-albumin adducts (22). Merlo et al. (52) estimated that the contribution of involuntary tobacco smoke exposure to 1-OHPyr urinary excretion would be similar to exposure among police officers working in a traffic setting. In addition, consistent with our findings in children, Tsai et al. (53) reported an average 9.6% increase in urinary 1-OHPyr in preschool children per one cigarette smoked by the child's father. The higher concentrations of urinary PAH metabolites in nonsmokers who are involuntary exposed to tobacco smoke compared with unexposed can be related to high PAH levels in the sidestream fraction of tobacco smoke, the main fraction to which nonsmokers are exposed (54-56).

In a controlled atmosphere experiment, high concentrations of several PAH compounds were measured in aged and diluted sidestream tobacco smoke particles (57). Increased levels of multiple PAH compounds have also been reported in field studies comparing smoking with control environments (58). In the present study, the statistically significant differences in PAH metabolites between involuntarily exposed and unexposed participants were observed for 1-OHPyr, 2-OHFle, 3-OHFle, 9-OHFle, 1-OHPhe, 2-OHPhe, and 3-OHPhe, but not for 9-OHPhe or 1-OHNap and 2-OHNap isomers, suggesting that involuntary tobacco smoke exposure could be a relevant source for these PAH metabolites. Overall, the higher concentrations of PAH metabolites in the urine of nonsmokers involuntarily exposed to tobacco smoke compared with the urine of unexposed nonsmokers suggest that inhalation of tobacco smoke–contaminated air contributes significantly to PAH excretions in urine.

Grilled/Broiled Meat Consumption

Diets that are rich in PAHs are recognized as one of the most important sources of PAH exposure for nonoccupationally exposed nonsmokers (17, 59). Several studies have reported elevated urinary PAH biomarkers, particularly 1-OHPyr, with consumption of foods that are rich in PAH, such as those cooked by open-flame methods. In a controlled experimental study of 21 nonoccupationally PAH-exposed volunteers, urinary levels of 1-OHPyr increased after consuming 170 g/d barbecued hamburgers for 5 days compared with baseline (17). Similarly, urinary excretion of 1-OHPyr glucuronide increased 10- to 80-fold following the ingestion of broiled beef (60). Compared with a control group, exposure to dietary PAH from charcoal-grilled meat resulted in a 4- to 12-fold increase of 1-OHPyr level in urine (61). However, few studies have evaluated the effect of dietary PAH exposure on other monohydroxylated metabolites, although Hoepfner et al. (49) did observe a 2-fold increase in urinary excretion of OHPhe in subjects with a PAH-rich diet.

In the present study, we found only a weak association between reported consumption of grilled/broiled meat in the past 24 hours and 1-OHPyr levels in urine, possibly related to incomplete assessment of all relevant food items and cooking methods. It is important to note that grilled/broiled meats contribute less than half the PAHs consumed through dietary sources (12). The associations, however, were stronger for 3-OHPhe, 9-OHPhe, 1-OHNap, and 2-OHNap, even after adjusting for smoking and other confounding factors, suggesting that these metabolites, rather than 1-OHPyr, may be relevant biomarkers for monitoring low-level PAH exposure related to intake of PAHs from foods.

The observed variability in the relationship of grilled/broiled meat consumption across individual PAH metabolites in urine may be explained by interindividual variation in doses and bioavailability of ingested PAHs, and possibly by interindividual variation in genetic polymorphisms that encode enzymes involved in PAH biotransformation as suggested by Rihs et al. (60, 62-65). Alternatively, the induction of metabolizing enzymes through chronic exposure could lead to differential metabolism of individual PAHs. Active smokers may metabolize ingested PAHs differently from unexposed individuals (66).

Other Sociodemographic Determinants

In our study, age and household income level, and to a lesser extent race/ethnicity and education attainment, were significant determinants of urinary excretion of PAH metabolites. The influence of age and race/ethnicity on PAH metabolite levels has not been extensively studied. The inverse association between low income and education levels with urinary excretion for most PAH metabolites after adjustment for tobacco exposure may reflect additional sources of PAH exposure, either inside or outside the home.

Strengths and Limitations

Important strengths add to the relevance of the study findings. First, this is a large study, multiethnic, and representative of the general U.S. population ≥6 years old. Second, we were able to evaluate multiple PAH metabolites in urine. Urine PAH levels integrate several sources of exposure and are considered validated markers, even at low levels. Third, involuntary exposure to tobacco smoke was defined by combining serum cotinine levels and self-reported measures of smoking status, thus reducing the likelihood of smoking status misclassification. Other strengths of this study include the ability to control for several relevant covariates, including dietary factors, the consistency of the findings by participant characteristics, and the high quality measures and procedures used by NHANES.

Several limitations must be considered. First, although we used a commonly used cutoff for cotinine (≥10 ng/mL; refs. 28, 45) to classify active versus involuntary smoke exposure, it is possible that some infrequent smokers who denied smoking remained classified as involuntarily exposed. Conducting sensitivity analyses using 5 ng/mL as a cutoff, however, did not substantially affect the study findings. Second, although PAH concentrations in food can vary depending on type of meat, method of preparation, cooking temperature, and fuel sources (67), NHANES dietary data were limited, thus restricting our ability to estimate and control for those aspects related to PAH content in food items. This might have affected our analysis of the association between grilled or broiled meat and PAH levels. It is unlikely to have confounded the relationship between tobacco exposure and PAH metabolites, however, because our findings were consistent according to participant characteristics such as differences in gender, ethnicity, education level, and age, including young children. Third, the possibility of reporting bias with regard to smoking status could not be ruled out. Current smokers who had not recently smoked a cigarette may have been classified as a nonsmoker if they incorrectly reported their smoking history. Similarly, nonsmokers with extreme levels of environmental tobacco exposure and consequent high levels of cotinine, such as those working in smoky environments, may have been classified as smokers. Although our study included subjects as young as 6 years, infants and preschool children were not evaluated because PAH measures were not available in NHANES data for children <6 years of age. Thus, we were unable to address the implications of involuntary smoke exposure for this important group. Other potential limitations include the cross-sectional design of NHANES, uncontrolled confounding, and potential biases resulting from nonparticipation and response error.

Conclusions

This study supports the hypothesis that involuntary and active tobacco smoke exposure is associated with urinary levels of several PAH metabolites. The clear dose-response relationship between levels of tobacco smoke exposure and elevated urinary concentrations of 1-OHPyr, 2-OHFle, 3-OHFle, 9-OHFle, 1-OHPhe, 2-OHPhe, and 3-OHPhe suggests that environmental tobacco smoke is a source of PAH exposure. The finding of involuntary exposure to tobacco smoke as a relevant source of mutagenic and carcinogenic PAH compounds underscores the public health relevance of this study and the need for public health and medical professionals to continue policy and educational efforts to minimize active and involuntary tobacco smoke exposure.

No potential conflicts of interest were disclosed.

Grant support: National Institute for Occupational Safety and Health Education and Research Center for Occupational Safety and Health at the Johns Hopkins Bloomberg School of Public Health grant T42 OH0008428. A. Navas-Acien was supported by a Clinical Investigator Award from the Flight Attendant Medical Research Institute.

1
IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Polynuclear aromatic compounds, part 1: chemical, environmental and experimental data. Lyon (France): IARC; 1983.
2
IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Polycyclic aromatic hydrocarbons, part 3. Lyon (France): IARC; 1984.
3
National air pollutant emission trends, 1900-1998: U.S. EPA and the states—working together for cleaner air! Report No. EPA-454/R-00-002. Research Triangle Park (NC): United States Environmental Protection Agency, Office of Air Quality, Planning and Standards; 2000.
4
EPA. Integrated Risk Information System (IRIS) [database on the Internet]. Boca Raton (FL): Lewis Publishers. [updated 2008 Feb 5; cited 2008 Dec 4]. Available from: http://www.epa.gov/iris/intro.htm.
5
Perera F, Tang D, Whyatt R, Lederman SA, Jedrychowski W. DNA damage from polycyclic aromatic hydrocarbons measured by benzo[a]pyrene-DNA adducts in mothers and newborns from Northern Manhattan, the World Trade Center Area, Poland, and China.
Cancer Epidemiol Biomarkers Prev
2005
;
14
:
709
–14.
6
Petruzzelli S, Celi A, Pulera N, et al. Serum antibodies to benzo(a)pyrene diol epoxide-DNA adducts in the general population: effects of air pollution, tobacco smoking, and family history of lung diseases.
Cancer Res
1998
;
58
:
4122
–6.
7
Castano-Vinyals G, Cantor KP, Malats N, et al. Air pollution and risk of urinary bladder cancer in a case-control study in Spain.
Occup Environ Med
2008
;
65
:
56
–60.
8
IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Tobacco smoke and involuntary smoking. Lyon (France): IARC; 2004.
9
Straif K, Baan R, Grosse Y, et al. Carcinogenicity of polycyclic aromatic hydrocarbons.
Lancet Oncol
2005
;
6
:
931
–2.
10
Agency for Toxic Substances and Disease Registry (ATSDR). Public health statement for polycyclic aromatic hydrocarbons (PAHs). Atlanta (GA): U.S. Department of Health and Human Services, Public Health Service; 1995.
11
Jongeneelen FJ. Biological monitoring of environmental exposure to polycyclic aromatic hydrocarbons; 1-hydroxypyrene in urine of people.
Toxicol Lett
1994
;
72
:
205
–11.
12
Phillips DH. Polycyclic aromatic hydrocarbons in the diet.
Mutat Res
1999
;
443
:
139
–47.
13
Strickland P, Kang D. Urinary 1-hydroxypyrene and other PAH metabolites as biomarkers of exposure to environmental PAH in air particulate matter.
Toxicol Lett
1999
;
108
:
191
–9.
14
Grimmer G, Brune H, Dettbarn G, Naujack KW, Mohr U, Wenzel-Hartung R. Contribution of polycyclic aromatic compounds to the carcinogenicity of sidestream smoke of cigarettes evaluated by implantation into the lungs of rats.
Cancer Lett
1988
;
43
:
173
–7.
15
Shields PG. Epidemiology of tobacco carcinogenesis.
Curr Oncol Rep
2000
;
2
:
257
–62.
16
IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Certain polycyclic aromatic hydrocarbons and heterocyclic compounds. Lyon (France): IARC; 1973.
17
van Rooij JG, Veeger MM, Bodelier-Bade MM, Scheepers PT, Jongeneelen FJ. Smoking and dietary intake of polycyclic aromatic hydrocarbons as sources of interindividual variability in the baseline excretion of 1-hydroxypyrene in urine.
Int Arch Occup Environ Health
1994
;
66
:
55
–65.
18
Dor F, Haguenoer JM, Zmirou D, et al. Urinary 1-hydroxypyrene as a biomarker of polycyclic aromatic hydrocarbons exposure of workers on a contaminated site: influence of exposure conditions.
J Occup Environ Med
2000
;
42
:
391
–7.
19
Goldman R, Enewold L, Pellizzari E, et al. Smoking increases carcinogenic polycyclic aromatic hydrocarbons in human lung tissue.
Cancer Res
2001
;
61
:
6367
–71.
20
Lafontaine M, Champmartin C, Simon P, Delsaut P, Funck-Brentano C. 3-Hydroxybenzo[a]pyrene in the urine of smokers and non-smokers.
Toxicol Lett
2006
;
162
:
181
–5.
21
Scherer G, Conze C, Tricker AR, Adlkofer F. Uptake of tobacco smoke constituents on exposure to environmental tobacco smoke (ETS).
Clin Investig
1992
;
70
:
352
–67.
22
Crawford FG, Mayer J, Santella RM, et al. Biomarkers of environmental tobacco smoke in preschool children and their mothers.
J Natl Cancer Inst
1994
;
86
:
1398
–402.
23
Centers for Disease Control and Prevention (CDC), National Center for Health Statistics (NCHS). National Health and Nutrition Examination Survey Data (NHANES), 1999-2000 [database on the Internet]. Hyattsville (MD): U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. [cited 2008 Dec 4]. Available from: http://www.cdc.gov/nchs/about/major/nhanes/nhanes99_00.htm.
24
Centers for Disease control and Prevention (CDC), National Center for Health Statistics (NCHS). National Health and Nutrition Examination Survey Data (NHANES): analytic and reporting guidelines [homepage on the Internet]. Hyattsville (MD): U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. [updated 2004 June; cited 2008 Dec 3]. Available from: http://www.cdc.gov/nchs/data/nhanes/nhanes_general_guidelines_june_04.pdf.
25
Smith CJ, Huang W, Walcott CJ, Turner W, Grainger J, Patterson DG, Jr. Quantification of monohydroxy-PAH metabolites in urine by solid-phase extraction with isotope dilution-GC-MS.
Anal Bioanal Chem
2002
;
372
:
216
–20.
26
Huang W, Smith CJ, Walcott CJ, Grainger J, Patterson DG. Comparison of sample preparation and analysis using solid-phase extraction and solid-phase microextraction to determine monohydroxy PAH in urine by GC/HRMS.
Polycyclic Aromatic Compounds
2002
;
22
:
339
–51.
27
Weitzman M, Cook S, Auinger P, et al. Tobacco smoke exposure is associated with the metabolic syndrome in adolescents.
Circulation
2005
;
112
:
862
–9.
28
Benowitz NL. Cotinine as a biomarker of environmental tobacco smoke exposure.
Epidemiol Rev
1996
;
18
:
188
–204.
29
Pirkle JL, Flegal KM, Bernert JT, Brody DJ, Etzel RA, Maurer KR. Exposure of the US population to environmental tobacco smoke: the Third National Health and Nutrition Examination Survey, 1988 to 1991.
JAMA
1996
;
275
:
1233
–40.
30
U.S. Census Bureau. How the Census Bureau measures poverty (official measure) [homepage on the Internet]. U.S. Census Bureau, Housing and Household Economic Statistics Division. [updated 2008 Aug 26; cited 2008 Dec 3]. Available from: http://www.census.gov/hhes/www/poverty/povdef.html.
31
U.S. Department of Agriculture (USDA). USDA Food and Nutrient Database for Dietary Studies, 1.0 [database on the Internet]. Beltsville (MD): Agricultural Research Service, Food Surveys Research Group. 2004 - [cited 2008 Dec 3]. Available from: http://www.ars.usda.gov/Services/docs.htm?docid=12082.
32
Centers for Disease Control and Prevention (CDC), National Center for Health Statistics (NCHS). National Health and Nutrition Examination Survey Data (NHANES). CDC growth charts: United States [database on the Internet]. Hyattsville (MD): U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. [cited 2008 Dec 3]. Available from: http://www.cdc.gov/nchs/about/major/nhanes/growthcharts/charts.htm.
33
Ogden CL, Kuczmarski RJ, Flegal KM, et al. Centers for Disease Control and Prevention 2000 growth charts for the United States: improvements to the 1977 National Center for Health Statistics version.
Pediatrics
2002
;
109
:
45
–60.
34
Centers for Disease Control and Prevention (CDC), National Center for Health Statistics (NCHS). National Health and Nutrition Examination Survey Data (NHANES), 2001-2002 [database on the Internet]. Hyattsville (MD): U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. [cited 2008 Dec 3]. Available from: http://www.cdc.gov/nchs/about/major/nhanes/nhanes01-02.htm.
35
Trevisan A. Concentration adjustment of spot samples in analysis of urinary xenobiotic metabolites.
Am J Ind Med
1990
;
17
:
637
–42.
36
Barr DB, Wilder LC, Caudill SP, Gonzalez AJ, Needham LL, Pirkle JL. Urinary creatinine concentrations in the U.S. population: implications for urinary biologic monitoring measurements.
Environ Health Perspect
2005
;
113
:
192
–200.
37
Grainger J, Huang W, Patterson DG, Jr., et al. Reference range levels of polycyclic aromatic hydrocarbons in the US population by measurement of urinary monohydroxy metabolites.
Environ Res
2005
;
100
:
394
–423.
38
Viau C, Vyskocil A, Martel L. Background urinary 1-hydroxypyrene levels in non-occupationally exposed individuals in the Province of Quebec, Canada, and comparison with its excretion in workers exposed to PAH mixtures.
Sci Total Environ
1995
;
163
:
191
–4.
39
Gundel J, Mannschreck C, Buttner K, Ewers U, Angerer J. Urinary levels of 1-hydroxypyrene, 1-, 2-, 3-, and 4-hydroxyphenanthrene in females living in an industrial area of Germany.
Arch Environ Contam Toxicol
1996
;
31
:
585
–90.
40
Levin JO. First international workshop on hydroxypyrene as a biomarker for PAH exposure in man—summary and conclusions.
Sci Total Environ
1995
;
163
:
164
–8.
41
Zhou J, Wang T, Huang Y, Mao T, Zhong N. Size distribution of polycyclic aromatic hydrocarbons in urban and suburban sites of Beijing, China.
Chemosphere
2005
;
61
:
792
–9.
42
Mumtaz M, George J. Toxicological profile for polycyclic aromatic hydrocarbons. Atlanta (GA): Agency for Toxic Substances and Disease Registry, U.S. Department of Health and Human Services; 1995.
43
Zhao ZH, Quan WY, Tian DH. Urinary 1-hydroxypyrene as an indicator of human exposure to ambient polycyclic aromatic hydrocarbons in a coal-burning environment.
Sci Total Environ
1990
;
92
:
145
–54.
44
Centers for Disease Control and Prevention. Cigarette smoking among adults—United States, 2004.
Morb Mortal Weekly Rep
2005
;
54
:
1121
–4.
45
Pirkle JL, Bernert JT, Caudill SP, Sosnoff CS, Pechacek TF. Trends in the exposure of nonsmokers in the U.S. population to secondhand smoke: 1988-2002.
Environ Health Perspect
2006
;
114
:
853
–8.
46
Jongeneelen FJ, van Leeuwen FE, Oosterink S, et al. Ambient and biological monitoring of cokeoven workers: determinants of the internal dose of polycyclic aromatic hydrocarbons.
Br J Ind Med
1990
;
47
:
454
–61.
47
Levin JO, Rhen M, Sikstrom E. Occupational PAH exposure: urinary 1-hydroxypyrene levels of coke oven workers, aluminium smelter pot-room workers, road pavers, and occupationally non-exposed persons in Sweden.
Sci Total Environ
1995
;
163
:
169
–77.
48
Jacob P III, Wilson M, Benowitz NL. Determination of phenolic metabolites of polycyclic aromatic hydrocarbons in human urine as their pentafluorobenzyl ether derivatives using liquid chromatography-tandem mass spectrometry.
Anal Chem
2007
;
79
:
587
–98.
49
Hoepfner I, Dettbarn G, Scherer G, Grimmer G, Adlkofer F. Hydroxy-phenanthrenes in the urine of non-smokers and smokers.
Toxicol Lett
1987
;
35
:
67
–71.
50
Preuss R, Koch HM, Wilhelm M, Pischetsrieder M, Angerer J. Pilot study on the naphthalene exposure of German adults and children by means of urinary 1- and 2-naphthol levels.
Int J Hyg Environ Health
2004
;
207
:
441
–5.
51
Scherer G, Frank S, Riedel K, Meger-Kossien I, Renner T. Biomonitoring of exposure to polycyclic aromatic hydrocarbons of nonoccupationally exposed persons.
Cancer Epidemiol Biomarkers Prev
2000
;
9
:
373
–80.
52
Merlo F, Andreassen A, Weston A, et al. Urinary excretion of 1-hydroxypyrene as a marker for exposure to urban air levels of polycyclic aromatic hydrocarbons.
Cancer Epidemiol Biomarkers Prev
1998
;
7
:
147
–55.
53
Tsai HT, Wu MT, Hauser R, et al. Exposure to environmental tobacco smoke and urinary 1-hydroxypyrene levels in preschool children.
Kaohsiung J Med Sci
2003
;
19
:
97
–104.
54
U.S. Department of Health and Human Services. The health consequences of involuntary exposure to tobacco smoke: a report of the Surgeon General. Atlanta (GA): U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, Coordinating Center for Health Promotion, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health; 2006.
55
Nelson E. The miseries of passive smoking.
Hum Exp Toxicol
2001
;
20
:
61
–83.
56
Lodovici M, Akpan V, Evangelisti C, Dolara P. Sidestream tobacco smoke as the main predictor of exposure to polycyclic aromatic hydrocarbons.
J Appl Toxicol
2004
;
24
:
277
–81.
57
Baek S, Jenkins RA. Characterization of trace organic compounds associated with aged and diluted sidestream tobacco smoke in a controlled atmosphere—volatile organic compounds and polycyclic aromatic hydrocarbons.
Atmos Environ
2004
;
38
:
6583
–99.
58
Jenkins RA, Guerin MR, Tomkins BA. The chemistry of environmental tobacco smoke: composition and measurement. 2nd ed. Boca Raton: Lewis Publishers; 2000.
59
Lioy PJ, Greenberg A. Factors associated with human exposures to polycyclic aromatic hydrocarbons.
Toxicol Ind Health
1990
;
6
:
209
–23.
60
Kang DH, Rothman N, Poirier MC, et al. Interindividual differences in the concentration of 1-hydroxypyrene-glucuronide in urine and polycyclic aromatic hydrocarbon-DNA adducts in peripheral white blood cells after charbroiled beef consumption.
Carcinogenesis
1995
;
16
:
1079
–85.
61
Buckley TJ, Lioy PJ. An examination of the time course from human dietary exposure to polycyclic aromatic hydrocarbons to urinary elimination of 1-hydroxypyrene.
Br J Ind Med
1992
;
49
:
113
–24.
62
Viau C, Diakite A, Ruzgyte A, et al. Is 1-hydroxypyrene a reliable bioindicator of measured dietary polycyclic aromatic hydrocarbon under normal conditions?
J Chromatogr B Analyt Technol Biomed Life Sci
2002
;
778
:
165
–77.
63
Alexandrie AK, Warholm M, Carstensen U, et al. CYP1A1 and GSTM1 polymorphisms affect urinary 1-hydroxypyrene levels after PAH exposure.
Carcinogenesis
2000
;
21
:
669
–76.
64
Nerurkar PV, Okinaka L, Aoki C, et al. CYP1A1, GSTM1, and GSTP1 genetic polymorphisms and urinary 1-hydroxypyrene excretion in non-occupationally exposed individuals.
Cancer Epidemiol Biomarkers Prev
2000
;
9
:
1119
–22.
65
Rihs HP, Pesch B, Kappler M, et al. Occupational exposure to polycyclic aromatic hydrocarbons in German industries: association between exogenous exposure and urinary metabolites and its modulation by enzyme polymorphisms.
Toxicol Lett
2005
;
157
:
241
–55.
66
Kim JH, Sherman ME, Curriero FC, Guengerich FP, Strickland PT, Sutter TR. Expression of cytochromes P450 1A1 and 1B1 in human lung from smokers, non-smokers, and ex-smokers.
Toxicol Appl Pharmacol
2004
;
199
:
210
–9.
67
Guillen MD, Sopelana P, Partearroyo MA. Food as a source of polycyclic aromatic carcinogens.
Rev Environ Health
1997
;
12
:
133
–46.