State agriculture officials today ordered a temporary ban in Michigan on the sale of all products containing and nationally used wood preservative and insecticide pentachlorophenol (PCP).
The sales ban followed last week's discovery that eight Michigan dairy herds are contaminated with PCP, which sometimes contains extremely poisonous dioxins.
The PCP contamination in Michigan threatens a state still suffering from a chemical disaster to its agriculture industry that began almost three years ago when polybrominated biphenls (PBBs), a fire retardant, were discovered in dairy herds.
But white PBB contamination, which caused the destruction of over 35,000 hogs, cattle and sheep, was limited almost entirely to Michigan, officials said the PCP contamination has national implications.
PCP has been manufactured for over 40 years and is used over the country in a variety of materials, from stain for picnic tables to treatment of telephone poles.
"Certainly if herds in Michigan have the problem, herds elsewhere do, too," said a spokesman for the state's Agriculture Department.
But Michigan officials said the dioxins, which can be produced inadvertently as a by-product in PCP manufacture, are the dangerous substances and not PCP itself.
Dr. Thomas Corbett, a researcher at the University of Michigan, claimed the dioxins are one of the "most toxic chemicals known to mankind."
Four companies in the United States manufacture PCP - Dow Chemical, Monsanto, Reichold and Vulcan - and about 800 companies make compounds that use PCP. Dioxins may be presented in some PCP brands, depending on quality control during manufacture.
Although eight Michigan herds were quarantined for PCP contamination, dioxins have been found in only one herd so far. Cows in the other seven herds are still being tested. The herds were housed in wooden structures treated with PCP, and officials say the cows became contaminated by licking the treated wood or breathing its fumes.
Symptoms in the cows included spontaneous abortions, breathing problems, persistent infections and deaths. It is not known what the chemicals effect on humans would be.