By Frank J. Dinan
DDT is currently the most effective mosquito control pesticide known. The environmental problems that its excessive use caused in the United States and worldwide were exposed in Rachel Carson’s famous book, “Silent Spring.”
This profligate use was instrumental in DDT being banned in the United States and throughout most of the world. However, the number of malaria deaths worldwide grew rapidly once DDT’s use declined. At least a million people soon were again dying each year from mosquito-borne malaria infections.
Most of those dying were African children. In 1973, after DDT had been used for mosquito control for 30 years, there were less than 400 malaria-caused deaths in South Africa.
While the environmental problems associated with DDT’s excessive past use are unquestioned, it has never been shown to cause a single human death. Studies have shown that DDT protects against malaria not only by killing mosquitos, but also by repelling them. Careful, tightly controlled use of DDT was reapproved by the United Nations health agency in 2006, 30 years after its use was banned. It is now carefully used only by trained technicians, in very limited quantities, and only under World Health Organization (WHO) specified guidelines.
Now, the mosquito-borne Zika virus is spreading more widely each day. The scientists at the Centers for Disease Control and Prevention are doing heroic work to bring it under control, but this will take time. No one knows how much time, and Congress has not provided the needed funds.
I suggest that it is reasonable to evaluate DDT’s use for emergency mosquito control under the tightly regulated conditions that the WHO now requires, and continue it only until the spread of the virus is controlled.
I realize that this is a controversial proposal, and cite the successful policy change that the United Nations made when faced with the sharp increase in malaria deaths that resulted when DDT was banned. That successful reinstatement of DDT’s use set a precedent for its use under emergency circumstances.
Choosing whether to use DDT is a classic case of risk/benefit analysis: deciding whether or not the benefits that would result from its use to control Zika’s spread outweigh the potential harm that could result from its use. That is a difficult decision to make, but one that I believe we should consider as we watch Zika spread throughout the world.
Understanding the virus more fully and developing a vaccine to combat it are laudable goals, but ones that could require much time. DDT is available, effective and we have finally learned to use it properly. Should we do so? I’m not certain, but two things I am sure of: DDT’s use should be evaluated, and I am glad it’s not my decision to make.
Frank J. Dinan, Ph.D., is emeritus professor of chemistry/biochemistry at Canisius College.