Our Stolen Futurea book by Theo Colborn, Dianne Dumanoski, and John Peterson Myers



Methoxychlor has powerful low level effects on prostate development in mice.

Methoxychlor, according to the US EPA, is used as an insecticide ("effective against biting flies, houseflies, and mosquito larvae") and is considered to be "an excellent replacement for DDT." In veterinary practices, methoxychlor is used as an ectoparasiticide (a medicine used to kill parasites that live on the exterior of their host). The EPA reports that the Reference Dose (RfD) for methoxychlor is 0.005 mg/kg/d. EPA estimates that consumption of this dose or less, over a lifetime, would not likely result in the occurrence of chronic, noncancer effects. The EPA has set the "Maximum Contaminant Level Goals" for methoxychlor in drinking water at 40 parts per billion (ppb) because EPA believes this level of protection would not cause any of the potential health problems described below.

A university website providing information about toxicity of pesticides says:

  Methoxychlor is one of a few organochlorine pesticides that have seen an increase in use since the ban on DDT in 1972. It is quite similar in structure to DDT, but has relatively low toxicity and relatively short persistence in biological systems. It is available in wettable and dustable powders, emulsifiable conentrates, granules, and an aerosol. It may be found in formulations with malathion, parathion, piperonyl butoxide, and pyrethrins.  

Despite these reassurances, evidence is emerging that methoxychlor is a potent endocrine disruptor.


Working in collaboration with vom Saal's laboratory, Wade Welshons et al. reported in 1999 that extremely low-level methoxychlor exposure causes dramatic changes in prostate and liver weights. Pregnant mice were fed 20 parts per billion methoxychlor per day. Prostate weight due to the resulting prenatal exposure to methoxychlor was approximately 60% greater than controls (right). This level of contamination is one half EPA's "Maximum Contaminant Level Goal" (i.e., what EPA recommends as the maximum allowable level in water) and was the lowest dose tested. It is virtually certain that lower levels have effects also.


  Welshon's et al. note, "An unexpected aspect of these results is that the prostate enlargement produced by methoxychlor appeared to be greater than the enlargement brought about by fetal exposure to estradiol, DES, or bisphenol A in prior studies. Estradiol is a form of natural estrogen. DES (diethylstilbestrol) is the most potent synthetic estrogen that had been discovered."  




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