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5 Formaldehyde
Pages 103-138

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From page 103...
... , 24-h, and 90-day exposure guidance levels for formaldehyde. The subcommittee's recommendations for formaldehyde exposure levels are provided at the conclusion of this chapter along with a discussion of the adequacy of the data for defining those levels and the research needed to fill the remaining data gaps.
From page 104...
... melamine-formaldehyde resins, which are used as adhesives in the production of particle board, fiber board, and plywood. Formaldehyde is also used in the manufacture of plastics, insulation, fertilizers, fungicides, biocides, corrosion inhibitors, embalming fluids, disinfectants, and household cleaners, and it is used in the textile industry in the production of permanent press and fire-retardant fabrics.
From page 105...
... . This review relies on those documents, which conclude that irritation of the eyes and upper respiratory tract is the primary human health effect of concern for setting exposure limits for both acute and chronic inhalation exposures to formaldehyde.
From page 106...
... Thus, the subcommittee placed more emphasis on reviewing adverse health effects in humans than in animals. Effects in Humans Accidental Exposures No reports of deaths in humans resulting from inhaled formaldehyde were mentioned in the literature, and only a few case reports of accidental inhalation exposures resulting in human intoxication were found in the reviews consulted (IARC 1995; ATSDR 1999; ACGIH 2001; Health Canada 2001; WHO 2002; Liteplo and Meek 2003; NAC 2003)
From page 107...
... , the most sensitive end point identified in the study literature is ocular and upper respiratory tract irritation. A concentration of 1 ppm appears to be the approximate threshold between complaints of symptoms ranging from none to mild to moderate with no clear concentration-response relationship or increase in complaints among exposed subjects compared with controls (subjects exposed to clean air)
From page 108...
... Occupational and Epidemiologic Studies Occupational and epidemiologic studies involve longer, more continuous exposure durations and a greater number of subjects but are less controlled for simultaneous exposures to other substances, such as irritants, solvents, or particulates. Many of these investigations suffer from uncertain
From page 109...
... Some studies involve workers exposed to formaldehyde used in their occupational settings, which included mortuaries, hospitals, and laboratories. In general, studies in workers associate irritation with lower concentrations of formaldehyde than those reported in the controlled human studies.
From page 110...
... . Unlike occupational exposures, residential exposures potentially involve continuous exposures more similar to those experienced by submariners (that is, 24 h per day rather than 8 h per day)
From page 111...
... and occupationally Krakowiak et al. exposed asthmatic subjects (10)
From page 112...
... subjects (previously complained about nonrespiratory effects of urea-formaldehyde foam insulation) No effects on pulmonary function parameters (FVC, FEV1, max and midexpiratory flow rate)
From page 113...
... 0, 0.2, 0.4, 0.8, 1.6 5h Healthy subjects (16) Andersen and No differences in nasal airway resistance or pulmonary function Molhave 1983 parameters; decrease in nasal mucus flow at all concentrations; no discomfort at 0.2 or 0.4 ppm for 2 h, some slight discomfort reported in the 3-5 h period (conjunctival irritation, dryness of nose and throat)
From page 114...
... ; irritation scored mild to mild-moderate (group means) ; small decreases in moderate exercise some pulmonary function parameters (FEV1, FVC, FEV3, but not FEF25(asthmatic subjects)
From page 115...
... 1984 Similar responses in airway resistance following exposure at 0, 1, or 3 ppm with and without exercise (exercise increased all responses) 0.03 to 3.2; 37 min Healthy subjects (two exposure groups of 33 and 48)
From page 116...
... Sim and Pattle 1957 Nasal and eye irritation (not severe) with mild lacrimation; adaptation to the eye irritation 20 Several Healthy subjects (2)
From page 117...
... Many of those studies are not directly useful for evaluating exposure limits in humans because of the very high exposure concentrations used. The studies in animals, however, included more continuous exposures under controlled conditions over longer time periods, such as 26 weeks, and provided supporting evidence for the nature of toxic effects, the target tissues, and the concentration-response relationship observed in human studies.
From page 118...
... , cellular lesions, such as cytolethality and hyperplasia, might develop in the nasal passages and, with increasing concentrations, in other areas of the respiratory system. Epithelial lesions of the upper respiratory tract observed in rats and monkeys were histologically similar, although regional differences in occurrence were evident.
From page 119...
... . Overall, studies in animals have demonstrated that the adverse effects of formaldehyde exposures, including nasal tumors (discussed below in the section on carcinogenicity)
From page 120...
... . Evidence from animal studies does not indicate that repeated inhalation exposures to formaldehyde have a direct effect on the immune system, although suggestive evidence indicates that formaldehyde might indirectly facilitate sensitization of the nasal tissues to high-molecular-weight allergens (ATSDR 1999)
From page 121...
... to various regions of the upper respiratory tract than to the administered dose (the ambient concentration of formaldehyde initially inhaled)
From page 122...
... The study authors concluded that the evidence for formaldehyde carcinogenicity in humans is unconvincing and that although the occurrences of sinonasal or nasopharyngeal cancer cannot be ignored, the small increase in lung cancer mortality (standardized mortality ratio = 1.28 [95% CI = 1.13-1.44]
From page 123...
... garment workers in three plants reported no nasal or nasopharyngeal cancers or increases in respiratory cancers with duration of formaldehyde exposure or with historical exposure when concentrations were presumably higher (Pinkerton et al.
From page 124...
... The recent findings from some epidemiologic studies of increased risks for higher-exposure groups and high-peak exposures are consistent with this general theory. TOXICOKINETIC AND MECHANISTIC CONSIDERATIONS Consistent with its action as an upper respiratory irritant, formaldehyde is a highly water-soluble vapor that is readily absorbed by the upper respiratory tract and is rapidly metabolized to formic acid or formate (IARC 1995; ATSDR 1999)
From page 125...
... The NASA spacecraft maximum allowable concentrations (SMAC) values, which may be more analogous to submarine exposure levels than other limits, are based on a Wisconsin mobile home study (1-h and 24-h SMACs)
From page 126...
... 1 Proposed AEGL-2 (8 h) 8 a The comparability of EEGLs and CEGLs with occupational and public health standards or guidance levels is discussed in Chapter 1, section "Comparison to Other Regulatory Standards or Guidance Levels." Abbreviations: ACGIH, American Conference of Governmental Industrial Hygienists; AEGL, acute exposure guideline level; ATSDR, Agency for Toxic Substances and Disease Registry; h, hour; min, minute; MRL, minimal risk level; NAC, National Advisory Committee; NASA, National Aeronautics and Space Administration; NIOSH, National Institute for Occupational Safety and Health; NRC, National Research Council; OSHA, Occupational Safety and Health Administration; PEL, permissible exposure limit; ppm, parts per million; REL, recommended exposure limit; SMAC, spacecraft maximum allowable concentration; STEL, shortterm exposure limit; TLV, Threshold Limit Value; TWA, time-weighted average.
From page 127...
... 1-Hour EEGL Exposure limits for formaldehyde should be set to prevent moderate irritation effects in the eyes and mucous membranes of submariners. Unfortunately, it is difficult to quantify a threshold for irritation because at the lowest levels the symptoms are subjective, individuals vary in sensitivity, and variable rates of background irritation occur in the population.
From page 128...
... The 24-h SMAC of 0.1 ppm, which is the same as the Navy's proposed value, was based on the lower end of the concentration range anticipated to cause eye irritation in 4% of subjects as reported in the Wisconsin mobile home study, in which TABLE 5-4 Emergency and Continuous Exposure Guidance Levels for Formaldehyde U.S. Navy Values (ppm)
From page 129...
... . CARCINOGENICITY ASSESSMENT The EPA cancer unit risk factor for assessing the upper-bound cancer risk associated with inhaled formaldehyde was developed in 1991 (EPA 2003)
From page 130...
... would not occur at lower doses, the EPA unit risk factor for formaldehyde overestimates the risk at doses not associated with cytotoxicity. A two-stage clonal growth model developed by CIIT (1999)
From page 131...
... In summary, the carcinogenicity assessment based on EPA's unit risk factor for formaldehyde indicates that exposure at the 0.3-ppm 90-day CEGL over a submariner's career would be associated with an upper-bound risk that is 3 times the risk goal of 1 in 10,000. The available evidence, however, strongly suggests that the risk from formaldehyde at high doses demonstrated in animals studies cannot be extrapolated to lower doses using the EPA's approach (Conolly et al.
From page 132...
... 1990. Human performance during experimental formaldehyde exposure.
From page 133...
... Presentation at the First Meeting on Emergency and Continuous Exposure Guidance Levels for Selected Submarine Contaminants, January 23, 2003, Washington, DC.
From page 134...
... 1990. Clinical and immunologic evaluation of 37 workers exposed to gaseous formaldehyde.
From page 135...
... 1998. Airway response to formaldehyde inhalation in asthmatic subjects with suspected respiratory formaldehyde sensitization.
From page 136...
... . Dosimetry modeling of inhaled formaldehyde: The human respiratory tract.
From page 137...
... 1986. Acute pulmonary response to formaldehyde exposure in healthy nonsmokers.
From page 138...
... 1987. An evaluation of respiratory effects following exposure to 2.0 ppm formaldehyde in asthmatics: Lung function, symptoms, and airway reactivity.


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