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Evidence is accumulating that atrazine (ATZ), cadmium ( Cd), Arsenic (As) and nitrate (NO3) have estrogenic activity. These environmental hormonally active agents (HHAs) may be carcinogenic. Evidence indicates that the herbicide atrazine may be a direct carcinogen based on its clastogenic effects and may also act as a promotor based on its ability to induce the aromatase enzyme. Arsenic and Cd have both been classified as human carcinogens by IARC. Arsenic has been implicated in the etiology of skin, lung, bladder and liver cancers and Cd has been associated with lung and prostate cancers. Nitrate exposure through drinking water has been associated with an increased risk for bladder cancer.

This study involves exposing MCF-7 cell lines to a mixture of ATZ, Cd, As and NO3 at environmentally relevant concentrations to study their clastogenic potential by flow karyotyping. The mixture of the chemicals was prepared using their maximum contaminant level (MCL) as a unit for concentration. Actively growing cells were exposed for seven days to 75 ppt estrogen, 3ppb, 5ppb, 10ppb and 10,000ppb representing 100% MCL of atrazine, Cd, As and NO3 respectively and 10%, 100%, and 1000% MCL of atrazine, cadmium, arsenic, and nitrate mixture.

Mitotic cells were selected by the addition of colemid and their nuclei were isolated by a propidium iodide (PI) hypotonic lysis method. Isolated nuclei were analyzed with a FACSCalibur at an excitation wavelength of 488nm provided by 5W argon ion laser. Histograms obtained in each analysis were analyzed manually, and the coefficients of variation (CV) of the largest chromosome were recorded. Analysis of variance (ANOVA) was performed on the CVs of the various treatments and a least significant difference (LSD) analysis were performed on the mean CVs of the various treatments. Significance were designated at p <0.05.

Preliminary results indicated that estrogen did not cause any flow karyotype damage. However the individual chemicals tested at their 100 % MCL did cause flow karyotype damage. The chemicals mixtures at a concentration as low as 10% MCL did cause flow karyotype damage indicating synergistic effect among these chemicals. The flow karyotype damage caused by Cd at 100% MCL (5ppb) was not significantly different from the damage caused by 1000% MCL of the mixture. This preliminary findings stress the importance of studying chemical mixtures instead of the traditional individual chemicals studies.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA