Problems with the Performance of Passive Monitors for Formaldehyde
The existing standard for occupational exposures to
formaldehyde,
promulgated by the Occupational Safety and Health Administration,
established a "permissible exposure limit" for formaldehyde of 3
parts
per million as an 8-hour time-weighted average concentration (TWA)
(1). Subsequently, when formaldehyde was recognized as a potential
occupational carcinogen, the National Institute for Occupational
Safety and Health (NIOSH) recommended that exposures be reduced to
the
lowest feasible levels (2). New technologies have emerged for
detecting formaldehyde in the environment; a principal innovation
is
the "passive monitor."
Passive monitors, produced as badges to be worn on clothing or
affixed to a wall, are devices that sample the environment for
hazardous substances, such as formaldehyde. They are "passive" in
that they rely on unassisted molecular diffusion of the
environmental
agent in the air onto a sorbent material; the sorbent is then
subjected to chemical analysis to determine the amount of
formaldehyde
adsorbed. This differs from the established practice of sampling,
which utilizes a mechanical air pump to direct air, at a known flow
rate, over a sorbent material, or through a liquid contained in an
impinger; the material in the impinger is then quantitatively
analyzed
for formaldehyde. From these results, an estimate is made of the
concentration of the agent in the tested air.
To study the efficacy of passive monitors, NIOSH developed
draft
specifications for performance, protocols for testing, and criteria
for evaluation (3). They tested passive formaldehyde monitors* now
being widely marketed in the United States. These tests compared
the
performance of the passive monitors with results from independent
testing using established traditional methods (NIOSH Physical and
Chemical Analysis Methods 125 (4), and 354 (5)), and
chromatographic
analysis of 2, 4, dinitrophenyl hydrazine-coated silica gel tubes
(6)
(Table 1).
Testing of passive monitors, as marketed, consistently produced
estimates of formaldehyde concentrations that were lower than those
determined by the established sampling methods. Equilibration of
the
badges in an atmosphere of high humidity (92%) before exposure to
the
test atmosphere provided results comparable to results from
traditional methods. This suggests that the discrepant performance
of
the passive monitors may be explained by a loss of moisture from
the
sorbent and/or operation in atmospheres with low humidity (based on
laboratory tests, up to 40%).
Based on these findings, NIOSH concluded that the use of such
badges, as marketed, cannot be relied on to produce consistently
accurate measures of formaldehyde in the environment. NIOSH has
notified the manufacturer of these findings.
Reported by Methods Research Br, Div of Physical Sciences and
Engineering, NIOSH, CDC.
Editorial Note
Editorial Note: Similar findings have been reported by other
investigators (7), and NIOSH and CDC's Center for Environmental
Health
have received a number of telephone calls from state and local
health
agencies and from private individuals concerning the household use
of
these devices. Passive monitors for formaldehyde have been used to
test for formaldehyde in the air of some 10,000 U.S. homes (8).
Based
on the findings reported above, the results of such tests should be
interpreted with caution.
References
Occupational Safety and Health Administration. Occupational
and
Safety Health Standards, General Industry. U.S. Department of
Labor. 29 CFR 1910.1000.
NIOSH current intelligence bulletin 34. Formaldehyde:
evidence
of carcinogenicity. U.S. Department of Health and Human
Services
publication (NIOSH) 81-111 (1981).
National Institute for Occupational Safety and Health. NIOSH
manual of analytical methods, Vol. I (2nd Ed.). U.S.
Department
of Health, Education, and Welfare publication (NIOSH) 77-157A,
P&CAM 125 (1977).
National Institute for Occupational Safety and Health. NIOSH
manual of analytical methods, Vol. VII (2nd Ed.). U.S.
Department
of Health and Human Services publication (NIOSH) 82-100, P&CAM
354
(1981).
Beasley RK, Hoffmann CE, Rueppel ML, Worley JW. Sampling of
formaldehyde in air with coated solid sorbent and determination
by
high performance liquid chromatography. Anal Chem
1980;52:1110-4.
Gammage RB, Hingerty BE, Womack DR, Hawthorne AR. Field
intercomparison of formaldehyde monitors suitable for
residential
indoor measurements. Paper no. 19 presented at the 1983
American
Industrial Hygiene Conference, Philadelphia, Pennsylvania, May
22-27, 1983.
Anders LW, Shor RM. Formaldehyde concentrations measured in
U.S.
residences by diffusional samplers and impingers. Paper no. 20
presented at the 1983 American Industrial Hygiene Conference,
Philadelphia, Pennsylvania, May 22-27, 1983.
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