Toxic mixes double trouble  
UPdate Fall 2001

What happens when pesticides and industrial pollutants combine?  Unpublished Health Canada research reveals that the mixtures are far more toxic than any substance on its own. This means that present federal safety tests of pesticides, which are done one by one, are seriously flawed. 

The scientists found that when pregnant rats were exposed to chemical mixes, 80% of the babies were born dead, and the surviving babies showed abnormal behaviour.  The mother rats had been exposed to a mix of chemicals chosen to match contaminants commonly found in the human body.

The research results have been known for over a year, and have been presented at two conferences.  Yet Health Canada has not made the results public.  Nor have they commented on the questions this research raises about present safety testing procedures. 

The theory that the danger of mixtures of chemicals can be substantially greater than the harm done by each one separately has existed for years.  This interaction is called "synergistic effect." Studying synergistic effects is more costly and complicated than testing substances individually, so little has been done.  The results of these tests surprised even the researchers, who found them "unexpectedly high."

Humans are not exposed to pesticides and other contaminants individually. Quebec government scientists have sampled water from 20 rivers in the province.  Most samples contain ten to fifteen pesticides. Samples from streams and groundwater near Lakes Erie and St. Clair found similar mixes. 

Meanwhile, Health Canada continues to assure the public that pesticides registered in Canada undergo thorough scientific assessment.