‘Inert’ ingredients in pesticides can be as harmful as the active ones

Every pesticide contains not only the ‘active’ ingredients designed to kill the pest but up to 90% of other ingredients (the equivalent of excipients in drugs) which are classed as ‘inert’ but which in fact ‘may be chemically active and toxic to humans.’ However, although the active ingredients in the pesticide have to be declared on the label, the ‘inert’ ingredients do not.

There are almost 3,000 substances formulated in pesticides as ‘inert’ ingredients, about 50% of which are moderately risky, according to the US Environmental Protection Agency (EPA). However, no toxicological tests are done on these ingredients and, because manufacturers often claim that inert ingredient information is protected as ‘confidential business information’, it has proved very difficult for scientists to evaluate long-term risks.

However, even without testing, recent scientific literature shows that some of these ‘inert’ substances can react with active ingredients increasing the later’s toxicity.

Inerts can also increase exposure to the toxic chemicals. For example, pesticide formulations including ‘inerts’ are more easily absorbed through the skin than active ingredients alone, they penetrate protective gloves more easily than active ingredients alone and they decrease the effectiveness of laundering of contaminated clothes. Inert ingredients can also increase the toxicity of pesticides to wildlife and plants.

Ongoing pressure from environmental groups in the US has forced the EPA to identify and list inert ingredients on their website, although the list contains no information about their toxicity or where they are used and, as the EPA cautions, is out of date!


First Publihed May 2007

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