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- Smoking
- Indirect exposure
- Ambient air
- Drinking water, food, and soil
Public Exposure
Aqueous formaldehyde is commonly encountered at low concentrations in cosmetics and personal care products in people’s everyday life. Because of its bactericidal and hence preservative properties, formaldehyde and its derivatives (including formaldehyde releasing products) are often added to a number of cosmetics and personal care toiletries, such as skin cleanser, moisturiser, shampoo, conditioner, shower gel, liquid hand wash, mouthwash and toothpaste (more details in Section 7.3.3). While some cosmetics, such as nail hardeners and nail polishes, may have higher levels of formaldehyde (up to 1%), the majority of other externally applied cosmetics and toiletries (either rinse-off or non rinse-off products) contain less than 0.2% free formaldehyde (see Table 7.6). Skin contact is the principal route of direct exposure, but exposure can also occur via eyes, mucous membranes, and respiratory epithelium. Small amounts of aqueous formaldehyde are also likely to be ingested during use of oral hygiene products. Therefore, although at low concentrations, direct exposure to formaldehyde is expected to be widespread and repeated with total exposure varying greatly, depending on the formulation and product type, route of exposure, individual habits and practices (such as frequency of use, duration of use, amount of product per application and demographics of use/misuse) and accidental exposure. Direct skin and inhalation exposure can also occur from the use of formaldehyde solvents in hobby activities (such as in DIY film processing), some paints and coatings in decorating activities, home care and cleaning products in housekeeping (such as fabric softeners, dishwashing liquids, and floor/carpet cleaners), and paper products (such as paper towels and grocery bags). The concentrations of free formaldehyde in the majority of these products are generally low (< 0.2%) and exposures are likely to be intermittent. Because of its high reactivity with biological macromolecules and rapid metabolism, formaldehyde exposure via the skin and inhalation is unlikely to cause systemic toxicity. Thus, the main concern as a consequence of cosmetic and consumer exposure remains at site of contact. Although concentrations of formaldehyde in these products are generally low, the direct exposure via cosmetic and consumer products is expected to be widespread and repeated.
Tobacco smoke is a source of formaldehyde emissions. In Australia, the ABS 2001 survey indicates that 24% of the adult population were current smokers, 26% were ex-smokers and 49% have never smoked (ABS, 2002). The average daily consumption of cigarettes among smokers (aged 16 years and over) was reported to be 17.8 in a survey conducted in Victoria in 1996-97 (Trotter et al., 1998). Environmental tobacco smoke is a combination of sidestream smoke, which passes directly from the burning tobacco into the air, and exhaled mainstream smoke from the smoker. Formaldehyde levels in mainstream smoke were reported at 70-100 µg/cigarette, depending on tobacco type and brand (based on US EPA 1992 data; NHMRC, 1997), with higher concentrations observed in non- filter cigarettes. Concentrations in sidestream smoke are often higher than in mainstream smoke due to its lower combustion temperature (IPCS, 2002). A sidestream smoke and mainstream smoke ratio, therefore, can vary between 0.1 and ~ 50 (NHMRC, 1997).
The principal route of indirect exposure is inhalation. Newton (2001) reported that Australians, whether at home, work, school, recreation or in-vehicle, spend up to 96% of their time indoors. According to a draft Exposure Assessment Handbook by enHealth Council (2003), approximately 42% of women and 22% of men spend more than 20 hours indoors each day. Given that there are a certain number of hours required to be indoors for sleep, approximately 18% of men and 6% of women spend less than 12 hours indoors each day. For both men and women, the greatest proportion of the populations spend more than 20 hours indoors each day and the proportion increases with age, being most marked in those over 65 years of age. Total individual exposure, thus, is likely to be closely associated with the time spent indoors. Groups of people who may be exposed to indoor air for the longest periods of time include the young, the elderly, and the chronically ill. Women tending to young families also spend more time at home. There is consistent evidence that formaldehyde levels are higher indoors than outdoors and the indoor to outdoor ratios range from 7-fold to 16-fold (see Table 13.10). Typically, the average levels of formaldehyde in the indoor air of established conventional homes and offices are about 15 ppb to 30 ppb. Higher formaldehyde levels have been recorded in mobile homes and relocatable buildings. In Australia, recent limited monitoring data showed an average formaldehyde level of 29 ppb (range 8 to 175 ppb) in occupied caravans and 100 ppb (range 10 to 855 ppb) in unoccupied caravans. No monitoring data in manufactured homes, such as park cabins, is available. It is estimated that approximately 160 000 Australians lived in mobile homes either permanently or while on holiday in 1996, with approximately 68 000 Australians living permanently in caravan parks (CASANZ, 2002). By 1999, over 250 000 caravans were registered in Australia, with the warmer climate states (such as Queensland, Western Australia and the Northern Territory) having a greater share of caravan park residents (ABS, 2000; CAZANZ, 2002). It is possible that people living in caravans in these States/Territories may be exposed to higher levels of formaldehyde, due to relatively high humidity and temperature. There are no recent Australian monitoring data for relocatable buildings including offices and classrooms. However, limited previous data showed high levels of formaldehyde in relocatable offices (range from 420 ppb to 830 ppb, with a mean of 710 ppb). In addition, new buildings or buildings with new furniture are likely to have higher formaldehyde levels as indicated by limited measured data and some studies considering age of building (Table 13.8). Therefore, people in these buildings would also be expected to be exposed to higher levels of formaldehyde. There is no information on the total number of relocatable buildings in Australia.
In Australia, mean levels of formaldehyde in ambient air range from 2 ppb to 18 ppb, with industrial areas reporting the highest levels. The data are limited, however, the values are in general agreement with the estimated annual average value of 5.5 ppb and the maximum 24-hour average value of 23.5 ppb for Australian urban environment using modelling technique (Table 13.7). A major source of formaldehyde in ambient air is the incomplete combustion of hydrocarbon fuels, especially from domestic heating and motor vehicles (Section 8.1). Industrial emissions are the major point sources, predominantly from mining, wood and paper industry, electricity supply and chemical and material manufacturing (Section 13.1.1). Thus, public exposure via ambient air may be higher in a heavily populated area or near some industries and during rush hour commutes, although there are no extensive measurements for these areas. Forest fires and other natural combustion sources can also emit formaldehyde to the ambient air (IPSC, 2002).
No data are available on the concentrations of formaldehyde in Australian drinking waters. In water, formaldehyde is formed by ozonation and chlorination of naturally occurring humic substances, contamination by accidental spills, or deposition from the atmosphere (IPCS, 2002). In ozonated drinking water concentrations of up to 30 µg/L have been reported overseas (NHMRC/ARMCANZ, 1996). Information on formaldehyde concentrations in food in Australia is not available. According to overseas data, formaldehyde occurs in small amounts in almost all common foods, ranging from 1-90 mg/kg (IPCS, 1989), and adult dietary intake is estimated at 11 mg/day with drinking water contributing less than 10% of this amount (NHMRC/ARMCANZ 1996). Accidental contamination of food may also occur through fumigation, the use of formaldehyde as a preservative, or through cooking (IPCS, 1989). Based on its low estimated Koc, high water solubility and its susceptibility to biotic and abiotic degradation (see Section 5), formaldehyde is not expected to significantly adsorb to soil particles and sediments, and thus it is likely to be present at negligible levels in these compartments. Therefore, public exposure to formaldehyde via drinking water, food and soil is expected to be low.
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