The study, published by the the Journal of Agricultural and Food Chemistry, shows that although food only contains small amounts of chlordane – a persistent organic pollutant (see related story)

– the compound accumulates in the human body and can lead to digestive and nervous system disorders.

The US EPA banned chlordane, used to control termites and other insects, in 1988. But because it was so widely used, nearly all farms – including organic farms – are affected. Technical chlordane, a synthetic pesticide made up of 147 different components, was once widely used at high concentrations in gardens and commercial farms throughout the US and Mexico. It has a half-life of 22 years in soil.

“Chlordane can be a problem in two ways” Mary Jane Mattina, the report’s lead researcher, told edie. “Either when a child eats the soil, or when a food crop is planted in soils that contain chlordane. The crops then take up the compound through their roots and into their edible flesh. That could potentially be a problem if there is a large amount of chlordane in the soil. Even organic food is not risk free – to get certification organic crops need only be grown using organic production methods, but some organic soil still contains chlordane. So organic is not necessarily an assurance that there are no traces of these POPs.”

The study, which is the first to examine plant absorption of aged chlordane, found that 12 of the vegetables studied absorbed some of the compound. Edible portions of carrots, potatoes, beets, spinach, lettuce, dandelion and courgette absorbed the largest amounts of chlordane. Lesser amounts were found in the edible portion of beans and aubergine. Tomatoes, peppers and corn took in some chlordane at the roots, but did not transfer it to the edible portion of the vegetables. Fruits did not seem to be similarly affected.

Mattina advises consumers to reduce the chances of consuming chlordane – a colourless, tasteless compound – by washing food in water before eating. Mattina also advises against planting near a house foundation that could have been treated with chlordane

Approximately six grams of the substance, held to be a possible human carcinogen by the EPA, can be fatal, according to the US Centers for Disease Control and Prevention in Atlanta.

The study found that carrots grown in highly chlordane-contaminated soil contained maximum levels of approximately five micrograms of chlordane per gram of peel. The rest of the carrot contained only trace amounts of the compound. At that rate, it would take eating more than one million carrots to even approach dangerous levels.

While peeling affected root crops can significantly reduce their chlordane content, other foods retain the chemical until they are eaten. Only ‘deep plowing’ to dilute the amount of chlordane in the soil can stop the uptake, the study found.

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