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More than two million California children attend school in portable classrooms that can be a significant source of exposure to airborne toxic chemicals and molds, according to state and federal data analyzed by Environmental Working Group (EWG).
Tests by school districts and indoor air quality specialists, plus extensive documentation of air toxins in mobile homes and similar structures, indicate that manufactured buildings emit hundreds of chemicals, including a number known to cause cancer, birth defects, brain and nerve damage, asthma and other illnesses. Of greatest concern are volatile organic compounds (VOCs) such as formaldehyde, benzene and toluene, which are emitted from the particle board, plywood, fiberglass, carpets, glues and other materials used in portables. Manufactured buildings, which are often prone to leaks, are also favored habitat for toxic molds that can cause nausea, nosebleeds, respiratory illness, and in extreme cases, even death.
How serious the health risks are in portable classrooms is hard to say. In many reported cases, students or teachers who suffered health problems in portables experienced short-term effects such as headaches or nausea that abated when they switched classrooms or ventila- tion deficiencies were corrected. But an exhaustive review of the scientific literature finds clear evidence that some portables can expose children to toxic chemicals at levels that pose an unac- ceptable risk of increasing their chances of developing cancer or other serious illness.
The chemicals found in portable classrooms are very similar to those found in conventional buildings. But the combination of tighter construction, fewer windows and inadequate ventilation in portables can lead to a greater buildup of toxic compounds. Data on the actual or average levels of VOCs and other air contaminants measured in portables are limited. Just as scarce are health-based government standards for exposure to contaminants in indoor air. But comparisons with standards for chronic exposure in outdoor air show that the outdoor exposure thresholds for formaldehyde are many times lower than levels that have been measured in portables (Figure 1).
In 1998 a Lawrence Berkeley National Laboratory scientist, considered one of the top experts on the issue, measured average levels of total VOCs in new mobile homes that were more than three times the indoor air quality standards set by the State of Washington and eight times the “comfort range” recommended by European experts (Hodgson 1998). (Table 1) Newer portable classrooms are required to provide better ventilation than mobile homes, but there is abundant anecdotal evidence that many portables are not properly ventilated — in some well-documented cases, the vents were found to never have been opened. In 1996 another Lawrence Berkeley Lab expert surveyed county health officers and air quality districts in California and found that the highest total VOC levels measured in a portable classroom were more than five times the Washington standard and more than 14 times the European comfort range (Daisey 1998).
The Washington standard and the European recommendation for indoor air allow continuous exposure to levels of toxins greater than acceptable outdoor concentrations when cancer or other chronic illnesses are considered. Based on risk assessment guidelines developed by the U.S. Environmental Protection Agency and the State of California, standards for chemicals in outdoor air, EWG calculated that for some children, exposure to formaldehyde at levels that have been measured in portables carries two to three times the increased risk of cancer permitted under the Clean Air Act (one additional case per million people). Similarly, exposure to benzene at levels measured in mobile homes (no measurements from portables are available) also carries the same level of increased risk of cancer (OEHHA 1999). These estimates assume that children are exposed to these carcinogens only during the time that they spend in portable classrooms.
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