Pesticides could be suppressing people's vitamin D levels, leading to deficiency and disease, say scientists. The warning follows the discovery that adults with high serum concentrations of organochlorine pesticides such as DDT have lower vitamin D levels. 

Exposure to lose doses of organochlorine pesticides has been previously linked to common diseases like type 2 diabetes, metabolic syndrome and cardiovascular disease. Vitamin D deficiency has similarly been associated with a rise in chronic diseases, but the two have been studied separately by researchers in different fields. 'The known associations between vitamin D deficiency and various diseases can be at least partly be explained by the common exposure to organochlorine pesticides,' says senior author Duk-Hee Lee of Kyungpook National University in Korea.

The US-Korean research team studied 1275 adults in the US aged 20 years or older and checked their blood for seven organochlorine pesticides. DDT and beta-hexachlorocyclohexane levels in study volunteers showed significant associations with lower serum concentrations of a vitamin D pre-hormone, 25-hydroxyvitamin D, which is the standard way to assess vitamin D levels in the body. The study sheds no light on how pesticides might influence vitamin D levels, though.   

Organochlorine pesticides were banned in the US decades ago, but are still detectable in people because they resist biodegradation in the environment, are lipophilic and accumulate in fat tissues. The World Health Organization still recommends the use of DDT to control mosquitoes in malarial regions and, while there is a global moratorium on spraying it on crops, illegal use in some countries is suspected. 

Levels of these chemicals are far lower than they were in the 1960s and 1970s, but Lee believes that they may still be significant because they act as endocrine disruptors. 'One characteristic of endocrine disruptors is that they show their possible harmful effects at levels lower than those which we currently think are safe,' Lee says. 'As chemicals like organochlorine pesticides travel a long distance through a variety of ways, humans can be exposed to these kinds of chemicals even though the country where they live does not use them anymore.'

'We have known for many years that DDT causes egg shell thinning,' says David Carpenter, director of the institute for health and environment at the University of Albany, New York.  'Since egg shell thickness is regulated by vitamin D, this study shows that the same suppression of vitamin D occurs in humans.' Carpenter says he is concerned about the push to bring DDT back into use as a potent pesticide against mosquitoes and other insects. 'It is very important to communicate how harmful DDT is to humans, not just mosquitoes.'

Anthony King 

 

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