Despite being banned almost thirty years ago, the pesticide DDT is still being widely found in human bodies, a leading health researcher says.
In a study of 146 human milk samples, most of the Persistent Organic Pollutants (POPs) found belonged to the DDT group, Professor Tze Wai Wong of The Chinese University of Hong Kong told the CleanUp 2011 Conference in Adelaide.
“DDT was only one type of contaminant that we found,” says Prof. Wong. “There were also dioxins, other organochlorines and banned pesticides that were once widely used in agriculture.
“Finding them in human milk indicates that these pollutants are still present in food chain, which means that they’re highly persistent and have a slow decline rate, or, worse still, they are still being used in some countries in food production– neither of which is good news for consumers.”
Prof. Wong explains that human uptake of dioxins and other POPs is mostly from contaminated food products that originate from places with heavily polluted soil and water. Dioxins can also enter the body through contaminated air.
“This problem is not confined to the Asia-Pacific, but can be found across the world. Apart from previous use of toxic pesticides, the community’s diet, its methods of waste disposal and its level of industrialisation can contribute to the uptake of POPs as well.”
For example, nations that produce more industrial waste risk the contamination of marine products when the waste is dumped into the ocean, he says.
Countries that incinerate their waste, like Japan or China, are particularly susceptible to dioxin contamination of food, as it is often released through burning.
“We suspect that high concentrations of DDT will be found in communities which consume large amounts of seafood, dairy products, cattle and poultry, as animals tend to bioconcentrate these toxins,” he says. “In this case, Western Europe, Scandinavia and Japan are particularly at risk.
“People in China and Japan may also have high concentrations of dioxin in their bodies, as waste is often incinerated which release this compound into the environment.”
Prof. Wong says his research tends to show up pollutants which were present in the human environment decades ago, and are still around, rather than more recent contaminants.
“We’re measuring what was prevalent in the past. Its persistence shows that we need to be cautious about what we are doing now, because the effects of today’s pollutants on health are not likely to be felt until some decades later.”
Prof. Wong recommends increased vigilance in food production, and especially over attempts to introduce new chemical compounds into the food chain.
“We have always been quick to come up with alternative chemicals to replace old or banned ones. This is often done without asking health researchers to examine their effects on the human body. Industry and scientists need to start working together better.
“We also need to choose our food more wisely and rethink our dietary choices. Nutrition and flavour shouldn’t be our only considerations when planning meals. We also need to think about which foods may also contain high levels of contaminants.”
It is also important to re-evaluate current methods of waste disposal, and their possible impact on human and environmental health, he says.
“Eventually, everything that we use has to end up somewhere. We need to make sure that the human body doesn’t end up as the ‘last stop’ for toxic compounds.”