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What's Up With Mixtures?

When it comes to mixing chemicals, the toxic sum can indeed be greater than the sum of its individual parts – a finding federal agencies have yet to heed when testing pesticides and other chemicals for safety.

A growing body of research shows that low levels of chemicals, in amounts far below the “safe” exposure levels set by the Environmental Protection Agency (EPA), become more toxic when mixed together – which is exactly the way in which we are most often exposed to them. That has researchers questioning whether the federal government’s safety tests for chemical exposures are inherently flawed by testing individual chemicals.

For example, one recent study by researchers at the University of California exposed frogs to a mixture of pesticides typically found in agricultural runoff. Individually, the pesticides were at levels 10 to 100 times below EPA standards, but frogs treated with this mix ran into a world of trouble. They were 10-12 percent smaller than untreated frogs; they developed holes in their thymus that harmed their ability to suppress disease; they developed high levels of hormones known to retard development; and, of those that lived, 70 percent of them succumbed to a pathogen the others were able to ward off. A separate study by the same researchers found that exposure to mixtures of these chemicals also turned testosterone into estrogen, making male frogs produce eggs instead of sperm.

This study supports previous research linking pesticide levels in men’s urine with low fertility, and elevated, but not unusual levels of a pervasive class of chemicals called ‘phthalates’ in mothers with reproductive problems in their sons.

People are rarely exposed to chemicals one at a time, the way lab rats are. Humans are exposed to many chemicals on a daily basis – from the plastic molecules that leach out of warm baby bottles to the additives used to toys and beach balls, to the linings used in food cans to the trace amounts of flame retardants and other persistent chemicals found hiding in the dust bunnies under your bed.

To read more about the study of pesticide mixtures and frogs, go to http://www.ourstolenfuture.org/NewScience/synergy/2006/2006-0124hayesetal.html.

For more information on pesticides and frogs visit http://www.ehponline.org/docs/2006/8067/abstract.html or click here.

And for more about problems with mixtures of chemicals, visit:

http://www.ourstolenfuture.org/NewScience/synergy/mixtures.htm

To read more about this and other environmental health issues, go to www.environmentalhealthnews.org, www.ourstolenfuture.org, or www.healthandenvironment.org.