Despite past assurances by health bodies that indoor DDT usage is safe, a review of recent studies on the link between DDT and human health has determined that the current practice of spraying the pesticide inside homes to fight malaria is leading to unprecedented and insufficiently monitored levels of exposure to it.
The review was done by a panel of experts and citizens.
After a review of nearly 500 epidemiological studies, the researchers developed a consensus statement calling for increased efforts to reduce exposure to DDT, to understand the health effects of exposure to DDT, and to develop alternatives to using DDT so that other methods could ultimately be relied upon for malaria control.
Examples of non-chemical measures to control malaria include the use of bed nets, draining sources of standing water or filling them up with soil, and the rapid diagnosis and treatment of malaria cases.
"We have to put our concerns in the context of people dying of malaria," said lead author Brenda Eskenazi, UC Berkeley professor of epidemiology and of maternal and child health at the School of Public Health.
"We know DDT can save lives by repelling and killing disease-spreading mosquitoes. But, evidence suggests that people living in areas where DDT is used are exposed to very high levels of the pesticide," she added.
According to Eskenazi, the only published studies on health effects conducted in these populations have shown profound effects on male fertility.
"Clearly, more research is needed on the health of populations where indoor residual spraying is occurring, but in the meantime, DDT should really be the last resort against malaria rather than the first line of defense," she said.
The researchers noted that the majority of studies on DDT have focused on the impact on wildlife and the environment.
Of the studies published on human health, almost all have dealt with populations exposed to low, background levels of DDT.
Nevertheless, some of those studies have suggested links between DDT and cancer risk, diabetes, developmental problems in fetuses and in children, and decreased fertility.
"Any studies conducted up to now on the human health effects from DDT exposure may not be relevant to the populations currently exposed to the pesticide through indoor residual spraying," said Eskenazi.
Moreover, most of the studies on DDT and human health were done in developed countries where the pesticide was banned in the 1970s, the researchers said.
According to co-author Jonathan Chevrier "DDT is now used in countries where many of the people are malnourished, extremely poor and possibly suffering from immune-compromising diseases such as AIDS, which may increase their susceptibility to chemical exposures."