A very short review of the toxicity, sampling, and mitigation of 4-Phenylcyclohexene in Indoor Air

The “new carpeting” smell results from various volatile organic compounds (VOCs), but one VOC is currently under increased scrutiny, 4-Phenylcyclohexene (4-PCH). 4-PCH is formed during the polymerization of styrene-butadiene glue used to attach the carpet backing on the pile. 4-PCH can further react with ozone (O3) in indoor environments and produce formaldehyde (a nasal irritant and known human carcinogen). The 4-PCH can be smelled at a low concentration of 1 part per billion (ppb), but even at these low concentrations, building occupants start experiencing prolonged headaches, eye irritation, and nausea. Children, especially toddlers, may be at higher risk of exposure since they play on the floor.

In 1987, affected EPA employees working at the Waterside Mall office building attributed irritation and neurotoxicity symptoms to newly installed carpets. Since then, animal toxicity studies showed the mice exposed to a 4-PCH of 0.4 ppm suffered severe toxicity together with mortality. There are no OSHA permissible exposure limits (PEL) in effect, but Leadership in Energy and Environmental Design (LEED) recommends a maximum concentration of 6.5 micrograms per cubic meter of 4-PCH using testing protocols consistent with the EPA Compendium of Methods for the Determination of Air Pollutants in Indoor Air.

The 4-PCH in the air can be easily collected with a calibrated pump into a glass sorbent tube. The tubes are further analyzed in the laboratory by OSHA's Chemical Sampling Information (CSI) method using GC/FID (gas chromatography / flame-ionizing detection). 4-PCH vapors personal exposure can also be measured by wearing a badge near the breathing zone or placed at a location for area sampling.

4-PCH off-gassing correlated with carpeting in a building are associated mainly with the time length the carpet was installed and the ventilation rate of the building. Remediations for 4-PCH include LEED recommended building flush-out, higher ventilation rates or even removal of the carpet and any carpet backing glue on the floor. During carpet rip-out other hazards may become airborne in the indoor air such as dust, dust mites and mold spores that can cause allergies and trigger asthma attacks.