Formaldehyde threshold levels

The need for control of formaldehyde emission from UF-bonded wood products has been recognized since Wittmann (4) reported in 1962 that extensive use of particleboard in furniture and building envelopes can cause indoor formaldehyde concentrations exceeding occupational threshold levels. However, it proved to be difficult to define the problem because formaldehyde emission from finished products was not regularly measured, and the correlation between emission rate and the environmental factors were not yet well established. 

Inasmuch as the indoor environment has the purpose to shelter occupants of buildings, it intrinsically tends to confine indoor pollutants. Sofar some 300 such pollutants have been identified (10) and, as mentioned earlier, radon and formaldehyde ( may reach occupational threshold levels. Indoor air quality is controlled by a... 

Several countries and agencies have responded to formaldehyde complaints by setting indoor air formaldehyde limits. As indicated above, these limits are usually arrived at by modifying the occupational threshold levels by a factor of ten. A short summary of such levels is shown in Table IV ... 

Alexandersson et al. [19] studied the effects of exposure of carpenters to formaldehyde, terpenes, and dust particles. The mean formaldehyde levels were far below the threshold value. The terpene levels were very low and frequently undetectable and dust levels were about one-tenth of the threshold levels. At the concentration levels recorded, no respiratory effects would be expected, yet dyspnea (shortness of breath), nose and throat irritation, chest tightness, and productive cough were observed. These results were reported without explanation. 

Polik W F, Guyer D R and Moore C B 1990 Stark level-crossing spectroscopy of Sq formaldehyde eigenstates at the dissociation threshold J. Chem. Phys. 92 3453-70... 

HVAC Materials Ventilation duct liners also react with ozone forming formaldehyde, acetone and C5—Ci0 aldehydes. Morrison et al. (1998) subjected new and used duct liners, air filters, sealants, sheet metal and other HVAC materials to ozone in small chambers. They observed secondary emissions of C5—Ci0 aldehydes from a new duct liner, a neoprene gasket and duct sealants. They predicted that secondary emissions from these materials could increase indoor aldehyde concentrations to levels comparable with odor thresholds. As will be discussed later, soiled HVAC materials also generate secondary products. 

Exposure to chromium(VI) can result in DNA-protein complexes, the identification of which may be useful as biomarkers of exposure to chromates (Costa 1991). Gel electrophoresis and immunochemical techniques were used to identify actin as the protein in a DNA-protein complex induced by potassium chromate in cultured Chinese hamster ovary cells. While the DNA-protein complexes induced by formaldehyde and ultraviolet light were different from those induced by chromate, actin was also identified as the protein in the complex induced by cis-platinum, indicating that the DNA-actin complex is not specific for chromium. However, an experiment in a group of four volunteers did not demonstrate an increase in DNA-protein crosslinks in leukocytes over a 240 minute period following the ingestion of 5 mg chromium(VI) as potassium dichromate in a 10 mg chromium/L solution or the same amount added to 300 mL of orange juice (presumably reducing chromium(VI) to chromium(III)) and diluted to 500 mL with deionized water (Kuykendall et al. 1996). Chromium levels in red cells, plasma and urine were increased. In a separate experiment in this study, a threshold dose of 52 pg chromium(VI)/L was determined for crosslink formation in cultured lymphoma cells. 

Alexandersson et al. studied the effects of exposure of carpenters to formaldehyde, terpenes, and dust particles. The mean formaldehyde levels were far below the threshold value. The terpenes levels were very low and... 

During the past 15 years formaldehyde exposures and emission limits have been significantly lowered. Occuptional threshold limits are now 1.0 ppm or lower in most countries, and actual industrial exposures are almost always half of this value or less. Indoor air standards of 0.1 ppm are now contemplated in several nations, following established procedures for correlating occupational levels of toxic chemicals with ambient air levels. Furthermore, emission standards for UF-bonded wood products have been developed that allow the prediction of formaldehyde levels under various product use conditions before formaldehyde emitting products are installed. 

Formaldehyde is another example of a mutagenic compound with evidence of nonlinearity. Based on limited evidence of respiratory cancer in humans and evidence of nasal tumors in rats and mice, ERA classifies formaldehyde as a probable human carcinogen. In rats, the most well-studied animal model for formaldehyde carcinogenesis, there is a threshold for tumor formation at 6 ppm. At levels below 6 ppm, formaldehyde induces DNA crosslinks in a dose-dependent manner wilh apparent low-dose linearity (Conolly et al. 2000 Slikko- et al. 2004). At doses above 6 ppm, concurrent with tumor formation, formaldehyde causes maiked cytotoxicity in the nasal passages of rats. 

In 1977 the Canadian goverrmient subsidized the introduction of UFFT in older homes to conserve energy. The UFFI proved to be unstable in some cases due to improper installation, and as a result formaldehyde levels in some homes exceeded the threshold limit value (TLV) of 0.10 ppm (120 (ig/m ). Ammonia was able to neutralize the acid, and it was also shown that the water-soluble polymeric amine, polyethyleneimine, could remove the liberated formaldehyde. Nmietheless, the Canadian government then paid the homeowners an estimated 272 million ( 5,000 to 57,700 homes) to remove the UFFI. The urea formaldehyde resin is commonly used as the adhesive resins in plywood and particle board and will initially release formaldehyde if not sealed. As more composite wood products find their way into buildings, greater concern about indoor air is warranted. 

Control limits are based on Regulations, Approved Codes of Practice, European Community directives, or Health and Safety Commission instructions, and are limits which should not be exceeded. Failure to comply with a control limit may result in enforcement action by a Health and Safety Executive Inspector. With some controlled substances (i.e. those with no minimum threshold below which adverse effects do not occur, or where short exposure to high concentrations cause injury) exposures may need to be reduced to the lowest levels justifiable on a cost/risk basis. The present strategy behind the application of control limits for exposure to relatively few substances, some of which are not highly toxic, is based on the recognition that these substances are very commonly used at work. Until a few years ago, a great many were used without any real control of exposure (e.g. asbestos, vinyl chloride and lead compounds). Some, such as methylene chloride, formaldehyde and styrene, have been shown more recently to be potentially very harmful, in both the short and the long term, at levels of exposure just above the limits set, and they are included because of their widespread use at work. 

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