Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants Volume 1 (1994) / Chapter Skim
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B4: Formaldehyde
B4: Formaldehyde
Pages 91-120
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From page 91... ...
B4 Formaldehyde King Lit Wong, Ph.D. Johnson Space Center Toxicology Group Biomedical Operations and Research Branch Houston, Texas PHYSICAL AND CHEMICAL PROPERTIES Formaldehyde is a colorless gas win a strong, pungent odor (TLV Committee, 1989; Sax, 1984)
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From page 92... ...
TOXICITY SUl\IlVIARY Acute formaldehyde exposure produces mainly mucosal irritation of the eye and upper respiratory tract in humans, and a long-term exposure leads to the production of nasal tumors in rodents. Formaldehyde also causes pulmonary Unction impairment and asthmatic reactions in sensitized individuals.
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From page 93... ...
From the data gathered in a survey conducted with 61 mobile-home residents in Wisconsin, the predicted percentages of residents wig eye irritation at different formaldehyde concentrations were as follows (Hanrahan et al., 1984~. FormaidebydeConcentraffon (ppm)
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From page 94... ...
It is, however, cliff~cult to accurately estimate the threshold concentration for formaldehycle's mucosal irritation effect. A few percentage of individuals respond to formaldehyde at as low as 0.1 ppm.
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From page 95... ...
(Holmstrom and Wilhelmsson, 1988~. In another report, runny nose, runny eyes, squamous metaplasia, dysplasia, and goblet-cell hyperplasia of He nasal mucosal have been found in workers exposed to 0.08-0.9 ppm of formaldehyde for about 10.5 y (Edling et al., 1988~.
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From page 96... ...
in squamous metaplasia and basal cell hyperplasia of the nasal mucosa (Wilmer et al., 19891. Most of the subchronic data on formalclehycle were based on cliscontinuous exposures.
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From page 97... ...
As mentioned above, a 13-w formaldehyde exposure at 10 ppm produced non-neoplastic changes in the nasal mucosa of rats (Woutersen et al., 1987; Feron et al., 1988~. However, a 13-w exposure at 20 ppm is known to cause squamous cell carcinoma, carcinoma in situ, and polyploid adenomas in rats (Feron et al., 1988~.
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From page 98... ...
Another case-control study with 544 woodworkers exposed to formaldehyde also failed to show a significant increase in the odds ratio for cancer in the upper respiratory tract (Partanen et al., 1990~. However, two case-control studies showed that employment in jobs wig known formaldehyde exposures was associated wig increased risks of nasal and sinus cancers (Hayes et al., 1986; Vaughn et al., 1986a,b)
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From page 99... ...
Developmental Toxicity Formaldehyde is not teratogenic in He rat (Saillenfait, 1989~. Inhalation exposure of pregnant rats, on clays 6-20 of gestation, to 20- or 40-ppm formaldehyde reduced fetal body weight, but it caused no malformations (Saillenfait, 1989~.
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From page 100... ...
, an irritant gas like formaldebycle, it is of interest to determine if inert particles will also potentiate formaldehyde's irritancy. In a Swedish study, in which the exposure levels were not measured, the respiratory symptoms and lung function in workers exposed to formaldehyde alone or formaldehyde with wood dust were compared (Holmstrom and Wilhelmsson, 1988~.
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From page 103... ...
103 no o on so ~on , ~ ~ cr.
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From page 104... ...
104 _, : ~ oo a: ;; .~ .= .8 c E ~ c c ~ ~ ~ c .o ~o c C E _ ad HE _ o ._ 4_ C)
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From page 107... ...
107 ~_^ Do Do _ Cal ~^ ~ ~_ ~_ ~ 2 i ~i' ~ ~ =~ ~ 1~1 ~ ~ 20 em ~'~ I;~ 1~ Lo ya =~i 3> ~ 2 !
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From page 108... ...
Therefore, a formaldehyde level low enough to prevent mucosal irritation will also prevent lung function impairment. There are no data on He formaldehycle concentrations required to sensitize individuals.
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From page 109... ...
Mucosal Irritation The short-term SMACs are clesigned for contingencies, so a minor degree of irritation is acceptable. Based on the Wisconsin mobile-home study, 0.4 ppm would cause eye irritation in about half of the individuals (or 75% of He individuals based on the upper 95% confidence limit)
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From page 110... ...
Quantitative risk assessments of carcinogens have traditionally been done using the exposure concentration as a measurement of the extent of the carcinogen exposure. However, to quantify the tumor risk of a carcinogen, such as formaldehyde, which shows a tumor response nonlinearly proportional to the exposure concentration in a bioassay, the dose at the target site is preferred over the exposure concentration as a measurement of the extent of exposure (Hoer et al., 1983~.
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From page 111... ...
Because the quantitative risk assessment with the molecular dosimetry data from the rat shows that a dose of 0.85 pmol/mg of DNA in He bioassay would yield a tumor risk of 140 cases/106 (~e upper 95% confidence limit) , a lifetime exposure of monkeys to 1-ppm formaldehyde at 6 in/d, 5 d/w would yield the same tumor risk.
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From page 112... ...
, the lifetime exposure concentration that would yield an upper 95 % confidence limit tumor risk of lo-4 was calculated to be 0.0~3 ppm. Therefore, the lifetime exposure concentration yielcling a 10-4 tumor risk from the traditional approach is about 20 times lower than that estimated with Me Chemical Industrial Institute of Toxicology's molecular dosimetry approach.
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From page 113... ...
an excess tumor risk of 10-4 = 0.0063 ppm x 146.7 = 0.9 ppm. Establishment of SMACs After the ACs for mucosal irritation and carcinogenesis are tabulated below, it is quite apparent that mucosal irritation is a more sensitive end point.
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From page 114... ...
1983. Eye irritation response of humans to formaldehyde.
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From page 115... ...
1984. Oxidation of formaldehyde and acetalclehyde by NAD+-clependent clehydrogenases In rat nasal mucosal homogenates.
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1984. Formaldehyde vapor in mobile homes: A cross sectional survey of concentrations and irritant effects.
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1986. Ultrastructural evaluation of acute nasal toxicity in the rat respiratory epithelium in response to formaldehyde gas.
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1990. Guidelines for Developing Spacecraft Maximum Allowable Concentrations for Space Station Contaminants.
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1988. Reanalysis of lung cancer mortality in the National Cancer Institute study on mortality among industrial workers exposed to formaldehyde.
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From page 120... ...
inhalation toxicity study of formaldehyde in male rats: 8-hour intermittent versus 8-hour continuous exposures. Toxicol.
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