Daily News Archive
From June 30, 2006
Requested on Triazine Cumulative Risk Assessment, August 21, 2006
Triazine-containing pesticides atrazine, simazine, and propazine and their three chlorinated degradates share a common neuroendocrine mechanism of toxicity which results in both developmental and reproductive effects in laboratory animals.
Atrazine is the second most commonly used agricultural pesticide in the U.S., and the most commonly detected pesticide in rivers, streams and wells. It is and a commonly used lawn herbicide. An estimated 76.4 million pounds of atrazine are applied in the U.S. annually. Atrazine has a tendency to persist in soils and move with water, making it a very common water contaminant. In fact, in a study of herbicides in surface waters in the midwest, atrazine exceeded EPA’s maximum contaminant levels for drinking water in over 50% of the sites sampled.
The widespread contamination of waterways with atrazine is a big concern for human and wildlife health. Atrazine is an endocrine disruptor, which can interfere with hormone function and can contribute to breast and testicular cancer, birth defects, and learning problems. It can affect levels of testosterone, progesterone, estrogen and thyroid hormones. Recent studies show that exposure to levels of atrazine found in the environment, even at levels far below EPA’s drinking water limits, demasculinizes tadpoles and turns developing frogs into hermaphrodites – with both male and female sexual characteristics. Several studies have shown that atrazine causes genetic damage, even at extremely low concentrations.
The high levels of herbicides in drinking water in agricultural areas has already caused health problems for some communities. For example, in Kentucky, researchers discovered that in counties where drinking water is contaminated with triazine herbicides, such as atrazine, there are increased numbers of breast cancer cases. A study in Missouri found that men in rural areas have lower sperm counts and quality than men in urban areas. The men with lower sperm counts and quality have higher concentrations of metabolites of the pesticides alachlor, diazinon, and atrazine in their urine, and the researchers believe that “…it is likely that men are ingesting these chemicals through their drinking water.”
EPA’s cummulative risk assessment process evaluates exposures
to pesticides that have a common mechanism, it does not evaluate the
cummulative exposure to a mixture of many different pesticides and other
toxics. A 1999 study found that mixtures of three common groundwater
contaminants—two pesticides and a fertilizer (aldicarb, atrazine,
and nitrate) —at concentrations allowable in groundwater by EPA
are capable of altering immune, endocrine, and nervous system functions
in mice. Additionally, frogs exhibit hermaphrodism when exposed to below
below-legal allowable levels of the herbicide atrazine in waterways.