From the 1970's to the early 1990s, Clayton Environmental Consultants was associated with Marsh & McLennan. Clayton Environmental Consultants performed a multitude of industrial hygiene studies in a variety of different industries.
A Clayton vice president, Dr. Jaswant Singh, wrote in the 1990 summer edition of Marsh's journal, Viewpoint, that, "Seven environmental risks pose the greatest liability exposures for business managers. They are hazardous waste, underground storage tanks, asbestos, carcinogens, air quality, indoor air quality and workplace exposures." In addition the article stated that, "When a pollutant is a known or suspected carcinogen, liabilities can be particularly grave." The article added that two of the most common carcinogens produced and used in commerce are asbestos and benzene.
Here is a 1981 report that Clayton did for the Caterpillar Tractor Company for asbestos fibers in certain air samples. And here are some air sampling results for Johns-Manville's Waukegan Illinois plant taken in August 1985 by Clayton Environmental Consultants.