Chronic exposure effects, atrazine

Fischer-Scherl, T., A. Veeser, R.W. Hoffmann, C. Kuhnhauser, R.D. Negele, and T. Ewringmann. 1991. Morphological effects of acute and chronic atrazine exposure in rainbow trout (Oncorhynchus mykiss). Arch. Environ. Contam. Toxicol. 20 454-461. 

Comprehensive mode of action studies support the conclusion that atrazine s effects on mammary tumors in the female SD rat are not relevant to humans. Furthermore, the chronic treatment no-effect levels determined in studies of the estrous cycle and mammary tumor response in the female SD rat are thousands of times higher than potential human exposure levels. 

Distributions of the MOE have been presented for individual exposure pathways (drinking water ingestion, dietary consumption, and herbicide handling), for the combined exposure pathways, and for atrazine and simazine both separately and combined. The MOEs have been calculated using a lower bound on the ED10 for the most sensitive effect in the most sensitive sex, strain, and species studied in chronic animal bioassays (i.e., mammary tumors in female SD rats). This mammary tumor response in the SD rat is not relevant to humans (IARC, 1999 United Kingdom, 2000 USEPA, 2003 Australia, 2004). 

The perception of triazines as safe compounds was modified when a chronic study conducted in the mid-1980s showed effects of atrazine on mammary tumors in rats (WHO 1990). As a result, manufacturers introduced restricted personnel exposure levels. The discovery that atrazine was often present where pesticide residues in drinking water exceeded the newly defined European limit of 0.1 /ig/h for any active ingredient, and subsequent media reports and public discussions that made no distinction between detection and hazard, promoted a feeling of insecurity toward the formerly unchallenged products. The development reached a level of misinformation such that atrazine was occasionally chosen as an instrument to attempt suicide (Section III). A virtually unlimited level of tolerance was fortunately experienced in these unfortunate attempts. 

---