Notes on Uses and Limitations of Environmental Sampling
November 26, 2001
The Board of Education, at the request of the Parents’ Association, has employed ATC Associates, Inc., to conduct extensive indoor and outdoor environmental monitoring at Stuyvesant. Results will be posted on the PA website.
Sampling results are tools; they are not answers. To be able to effectively interpret these measurements, it is helpful to understand both the proper uses as well as the limitations of environmental sampling.
METHODS
Levels of temperature, relative humidity, carbon monoxide, carbon dioxide, total volatile organic compounds (TVOCs), and respirable particulate matter (PM2.5) at Stuyvesant are being measured using “direct read” instrumentation, which provides an instantaneous “snapshot” of the level of the particular variable at a particular point in time. Asbestos and silica are sampled by pulling a known volume of air through a cassette which contains a filter. The filter is then removed and sent to a licensed laboratory for analysis. Fiberglass and lead dust are sampled by collecting dust samples for laboratory analysis.
Results of such sampling are applicable only to the times and locations at which the testing is performed. Thus, results may or may not be representative of conditions at other times or locations. In addition, it may be useful to look for “worst case” scenarios, with the understanding that while such results may not be representative of general conditions, they can serve to indicate what levels of exposure are possible and therefore what preventive measures are warranted.
Sometimes, there is disagreement over methods and equipment. For example, the New York City Department of Health has expressed concern that the instrument used by the BOE’s vendor to measure respirable particulate matter, the TSI Dust Trak, may exaggerate readings. TSI, the manufacturer of the instrument, acknowledges that this is possible, if the instrument is picking up other contaminants, including diesel exhaust and other combustion byproducts. As a result, although respirable particulates may be lower than measurements indicate, exposure to other harmful contaminants may be higher. Also, while actual readings with this instrument may or may not be accurate, relative measurements are still useful. For example, the PA’s environmental engineer used a TSI Dust Trak to compare indoor readings at Stuyvesant with indoor readings at Borough of Manhattan Community College across the street (both roughly equidistant from the ground zero and from the barge operation). He found significantly higher levels of respirable particulates indoors at Stuyvesant while outdoor levels at each school were identical, indicating that Stuyvesant’s ventilation system is much less effective in filtering out the particulate matter.
STANDARDS
Federal, state, and city standards provide legal limits for exposure to regulated substances. As such, they are useful tools for comparing and evaluating levels of contamination. Like all tools, however, they have proper and improper uses. Given current uncertainties about post-September 11th health concerns and given widespread citation of sampling results, it is important to be aware of the limitations of environmental and occupational health standards.
- Regulatory limits are politically determined rather than medically or scientifically determined. For example, although ongoing research spurs professional industrial hygiene organizations to frequently revise and make more protective their voluntary standards for exposure to hazardous substances, OSHA (the federal Occupational Safety and Health Administration) over the last 30 years has largely been prevented from updating its permissible exposure levels. Thus, the American Conference of Governmental Industrial Hygienists, a professional organization, has a recommended occupational exposure limit of 25 parts per million (ppm) for carbon monoxide, while the OSHA permissible exposure limit remains double that (50 ppm).
- Regulatory limits vary among the industrialized nations. Other nations’ standards are generally more protective than are those of OSHA or the EPA (Environmental Protection Agency). For example, the occupational exposure limit in Germany for carbon monoxide in Germany is 30 ppm, while in the U.S. it is 50 ppm.
- Regulatory limits should not be confused with “safe” limits. The professional industrial hygiene standards upon which virtually all OSHA permissible exposure levels were based (30 years ago) explicitly state that they are designed to protect “most” workers rather than all workers (i.e., some people will be adversely affected by exposure at levels lower than the standard).
- There are very few enforceable or applicable standards for indoor air quality situations such as those at Stuyvesant or other schools. Occupational health regulations are largely aimed at chemical exposures in industrial work settings.
- Chemical exposure standards generally do not take into account the fact that children may have increased susceptibility or the potential for more serious adverse health effects. The standards are based upon research conducted among an adult male worker population that is healthier than, and not representative of, the population at large.
- Potential health effects from simultaneous exposure to multiple chemical contaminants, such as may be occurring in the current uncertain environment, are neither regulated nor well understood.
CONCLUSION
Environmental monitoring results that fall within regulatory limits are not by themselves guarantees of a safe environment for students or staff. Other factors to be considered include the incidence of symptoms and illness among students, workers, and residents in the area, as well as the potential for additional uncontrolled releases of contaminants from the recovery operations.
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