This blog summarizes key findings from a case report conducted by William Hirzy and Rufus Morison (1989) titled “Carpet/4-Phenylcyclohexene Toxicity: The EPA Headquarters Case.” To be directed to the full article, please click HERE.
The development of toxicant-induced loss of tolerance (TILT) is by no means a new phenomenon. Evidence in fact dates back decades. Perhaps the earliest large-scale event to demonstrate this ironically occurred during the 1987 building renovation of the U.S. Environmental Protection Agency (EPA) headquarters in Washington D.C. With the installation of 27,000 square yards of new carpet in October of that year, the EPA had the unwelcomed opportunity to study firsthand the human health impacts of indoor air pollution. New carpet is known to release volatile organic compounds that can be hazardous to health. Though underappreciated at the time, the extent of this hazard can be substantial, and it did not go unnoticed in this case.
During the renovation, the newly laid carpet appeared to produce health complaints by employees. As progressively more carpet was laid, more and more complaints were registered. By January 1988, multiple employees had suffered severe reactions requiring hospitalization and EPA had brought on an industrial hygienist as well as its Emergency Response Team to compile and examine complaint reports and monitor indoor air quality.
By April 1988, symptoms reported by about 60 employees ranged in severity and included irritation of the eyes, nose, and throat to induction of what was then called “multiple chemical sensitivity,” now known as TILT. Dizziness, fatigue, nausea, difficulty concentrating, among other symptoms, was also reported. For employees who had become “TILTed,” symptoms were not always directly related to carpet emissions, but could be triggered by any number of environmental agents. In total, an estimated 124 of 2,000 employees became ill during this period due to the out-gassing of air pollutants from the new carpet. Of these, 17 were unable to work at their normal work stations, with eight having acquired sensitivities to previously tolerated substances such as perfumes, auto exhaust, and tobacco smoke. At least two employees quit their jobs as a result of illness.
The culprit most associated with the new carpet and consequently employee illness was a chemical known as 4-phenylcyclohexene, or 4-PCH. This chemical is produced as an undesirable product]during the manufacturing of styrene-butadiene rubber (SBR) latex, an adhesive used to bind carpets. The chemical is among the most frequently occurring semi-volatile organic contaminants emitted by SBR-backed carpets and is the major VOC responsible for their “new” smell.
Since the EPA headquarters case, both human and animal studies have shown exposure to 4-PCH and other carpet-related VOCs to cause adverse health effects. What makes this case particularly unique, however, is the well defined exposure event shared by such a large population—an unfortunate, yet valuable study opportunity. That a number of employees developed chemical sensitivities following exposure serves as important evidence supporting the existence of TILT, and provides an indication as to the prevalence of toxicant induced illness among the general working population.
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