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ARTICLE IN PRESS International Journal of Hygiene and Environmental Health xxx (2015) xxx–xxx
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Commentary
The formaldehyde dilemma Tunga Salthammer ∗ Fraunhofer WKI, Department of Material Analysis and Indoor Chemistry, Bienroder Weg 54 E, 38108 Braunschweig, Germany
a r t i c l e
i n f o
Article history: Received 11 February 2015 Received in revised form 23 February 2015 Accepted 23 February 2015 Keywords: Formaldehyde Guideline values Legislation Building products Secondary sources Indoor/outdoor
a b s t r a c t The IARC’s 2004 classification of formaldehyde as a human carcinogen has led to intensive discussion on scientific and regulatory levels. In June 2014, the European Union followed and classified formaldehyde as a cause of cancer. This automatically triggers consequences in terms of emission minimization and the health-related assessment of building and consumer products. On the other hand, authorities are demanding and authorizing technologies and products which can release significant quantities of formaldehyde into the atmosphere. In the outdoor environment, this particularly applies to combusting fuels. The formation of formaldehyde through photochemical smog has also been a recognized problem for years. Indoors there are various processes which can contribute to increased formaldehyde concentrations. Overall, legislation faces a dilemma: primary sources are often over-regulated while a lack of consideration of secondary sources negates the regulations’ effects. © 2015 Elsevier GmbH. All rights reserved.
Introduction Formaldehyde, first synthesized in 1855, is a highly important base chemical with a worldwide production of over 21 million tons. The majority is sold as an aqueous solution (37%). Industrial applications range from resins and adhesives for wood-based materials and fiber insulation through to textiles, biocides, paper and even cosmetics (Salthammer et al., 2010). In the early 1980s, discussions began regarding a possible regulation of the substance (Perera and Petito, 1983). In the early 80ies, Spengler and Sexton (1983) identified formaldehyde as one of the priority indoor air pollutants. One of the first indoor air guideline levels was set in Germany in 1977 as 0.1 ppm (= 0.125 mg/m3 under standard atmospheric conditions) (Salthammer, 2011). The World Health Organization (WHO) began in 1983 to treat formaldehyde as an indoor pollutant (World Health Organization, 1983) and in 1987 they published an indoor guideline level of 0.1 mg/m3 (0.08 ppm) (World Health Organization, 1987). The International Agency for Research on Cancer (IARC) classified formaldehyde as a human carcinogen (Group 1) in 2004 (International Agency for Research on Cancer, 2006). The German Ad hoc Working Group confirmed the German indoor guideline level of 0.1 ppm in 2006 as a safe concentration as regards the carcinogenic effect of formaldehyde in the human organism (Ad hoc, 2006). The assessment is based on formaldehyde being a threshold carcinogen, meaning that under a certain threshold,
∗ Tel.: +49 531 2155 213; fax: +49 531 2155 808. E-mail address: [email protected]
the risk is negligible. The WHO also confirmed their guideline value for formaldehyde as 0.1 mg/m3 in the year 2010 (World Health Organization, 2010). Wolkoff and Nielsen (2010) investigated the WHO assessment thoroughly and considered an air quality formaldehyde guideline of 0.1 mg/m3 to be protective against both acute and chronic sensory irritation in the airways in the general population. Moreover, the same authors state that the formaldehyde WHO guideline value is also considered defendable for prevention of all types of cancer, including lymphohematopoietic malignancies (Nielsen and Wolkoff, 2010). In the United States, the Office of Environmental Health Hazard Assessment (OEHHA) Reference Exposure Limits (REL) are defined as 3 g/m3 (chronic) to 94 g/m3 (acute, 1 h). No Reference Concentration for Chronic Inhalation Exposure (RfC) is currently defined by the US EPA (National Research Council, 2011). The European Commission classified formaldehyde as a 1B carcinogen and mutagen 2 on June 5th, 2014 in the ordinance EU 605/2014. Category 1B states that the carcinogenic effect has been demonstrated in animal trials and is probable for humans. The reclassification results in a series of consequences depending on national legislation. For example in Germany, the sum of carcinogenic substances in the exhaust air from industrial plants is limited to a mass concentration of 1 mg/m3 . Until now, formaldehyde has belonged to the category of organic substances with a total sum value of 20 mg/m3 . Over the years, a number of national authorities reassessed their indoor air guideline values and subsequently intend to agree with the WHO recommendation of 0.1 mg/m3 . This harmonization is a pragmatic step as the WHO value is very well assessed and justified. Moreover, the guideline
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Fig. 1. Regulated and non-regulated outdoor and indoor formaldehyde sources.
value is also not normally restrictive as formaldehyde conditions in normal living conditions tend to average between 0.02 and 0.04 mg/m3 (Salthammer et al., 2010). However, some countries have introduced guideline values for formaldehyde which are considerably below the WHO recommendation (Salthammer, 2011). Discussion Formaldehyde has actually always been a topic of environmental policy discussions as an air-polluting substance which primarily enters the body through respiration. Demands for particularly low guideline and limit values regularly arise and these arguments are often based on preventative aspects rather than toxicological and epidemiological factors. Currently the lowest guideline value is 10 g/m3 in France and is defined as a long-term exposure of >1 year. Nielsen et al. (2013) have comprehensively discussed the French approach and do not consider it as a reliable alternative to the WHO guideline. Product authorization is also seeing a tendency toward ever-stricter regulation. In 2014, Russia proposed a limit of 0.01 mg/m3 for furniture, measured under standardized conditions in the air of a test chamber. Although the demands for comprehensive consumer protection are of course to be welcomed, guideline and limit values which go way beyond the toxicologically justified necessity are not automatically to be considered positive. In addition, attempts to achieve lower indoor air concentrations are normally conducted by placing tighter limits on emissions from products. This, however, is a rather short-sighted approach, as the resulting indoor air concentrations are always a function of the climatic parameters and the living conditions. A good example of this is pre-fabricated houses. These are often made from wood-based materials using formaldehyde-based adhesives. Although the release of formaldehyde from wood-based materials has been significantly reduced on the manufacturing side in recent years, the indoor air concentrations in pre-fabricated houses have not decreased by the same amount (Salthammer et al., 2010). This is generally considered to be because the average air exchange rates have simultaneously been significantly reduced due to heat insulation. Formaldehyde concentrations and air exchange rates are inversely correlated (Institute of Medicine, 2011). The finding is not new and was already published more than 30 years ago by Gammage and Gupta (1984). Today, legislation on energy saving requires a certain air-tightness for living space, which often contradicts the need for sufficient natural air exchange. The operation of ventilation equipment with filtration systems is a possible alternative, but the energy consumption considerably increases as
target concentrations are reduced. This gives rise to the question of whether the technical effort required to minimize emissions and to reduce indoor air concentrations are always of corresponding benefit. This would certainly not seem to be the case when these target concentrations are excessively below well established guidelines. Another significant point concerns the plethora of unconsidered secondary sources of natural formaldehyde formation in indoor and outdoor space (see Fig. 1). Current legislation causes political developments for outdoor air to be diametrically opposed to administrative attempts to reduce formaldehyde concentrations in indoor air. On one hand this is caused by fuels and, especially, the increasing introduction of biofuels. Regardless of the undisputed need for sustainable fuels, this significant outdoor source of formaldehyde is thus being knowingly or unknowingly demanded or at least tolerated. The possible effects of fuel combustion on the formaldehyde concentration in the outdoor air are very well documented. As early as the 90s, i.e. during the introduction phase of biofuels, formaldehyde concentrations of over 100 g/m3 were measured in the air of Brazilian cities (Corrêa et al., 2010). Under practical conditions, combustion processes are never complete, so byproducts (especially with various carbonyl compounds) are always to be reckoned with (Sarathy et al., 2014). The effect of ethanol fuel blends on air pollution as well as the emission of formaldehyde from passenger cars has also been discussed by Jacobson (2012). According to a study by Pang et al. (2008), 62–161 mg of formaldehyde per kW engine performance and hour are released when combusting diesel and biodiesel–ethanol–diesel. These mass levels are considerable in their sum, but have so far hardly been taken into account. Industrial plants, however, are faced with strict emission reduction requirements. Forest fires are also a known natural formaldehyde source, but are difficult to characterize due to their uncontrolled conditions (Na and Cocker, 2008). During controlled combustion of wood in appropriate stoves for heating, around 200–1000 mg of formaldehyde are released per kg of wood depending on the type of wood and combustion process (Hedberg et al., 2002). A situation which can, at best, be described as inconsistent concerns indoor air. Decorative ethanol fires are subject to no significant admission procedure, but can cause extremely high formaldehyde concentrations under normal living conditions (Schripp et al., 2014). With the increasing pollution of the outdoor air with organic substances, photochemical reactions have established themselves as a significant source of formaldehyde. The ozonoloysis and the reactions of alkanes and alkenes with hydroxyl radicals and nitrous oxides are well known and have been described in detail. Photochemical smog as a
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later emit lower formaldehyde quantities than urea–formaldehyde adhesives, but may release traces of phenol. With all substitutes for formaldehyde there is the question of their health benefit, their cost-effectiveness and their overall ecological balance. Concluding remarks
Fig. 2. Range of formaldehyde concentrations in indoor and outdoor air. The range of current indoor guideline values between 8 ppb and 100 ppb is also provided. Reprinted from Salthammer (2013) with permission from John Wiley & Sons, Inc.
formaldehyde source is, especially in polluted megacities, a growing problem (Duan et al., 2008). Chemical reactions which lead to the formation of formaldehyde also take place indoors, despite the lack of the typical day/night atmospheric chemistry, but these are only controllable to a limited extent. The sources are normally terpene/ozone reactions or photocatalytic processes (Salthammer and Bahadir, 2009). When considering the facts discussed, it becomes clear that the political measures to limit formaldehyde (regardless of whether on the national or international level) currently face a dilemma. On one hand great efforts are being made to politically impose ever-lower formaldehyde limits on building product emissions and indoor air concentrations. Some of these are hardly justifiable from a prevention point of view and definitely not justifiable from a toxicological point of view. On the other hand one can observe a certain ambivalence, as secondary sources in indoor and outdoor spaces – and the influence of building and construction – generally remain unconsidered. Indoor formaldehyde concentrations are tending to fall, but outdoor concentrations are tending to rise. As pointed out earlier (Salthammer, 2013), this will eventually lead to the absurd situation that under certain conditions (e.g. in large cities with high air pollution) the formaldehyde concentration in the outdoor air will be higher than in the indoor air (see Fig. 2), which will then result in consequences for living and ventilation behavior. Stricter regulatory measures for building products can, in principle, further reduce the general population’s exposure to formaldehyde in indoor spaces. This is, however, generally already fairly below the WHO guideline value. Peak concentrations and high short-term exposure (e.g. by use of formaldehyde as a conservation agent in medical laboratories or by combusting ethanol or kerosene indoors) remain unaffected. Also, elevated formaldehyde concentrations such as those measured in the FEMA-supplied trailers following hurricane Katrina can only be minimized to a limited extent by emission restrictions. The emissions assessment of building products takes place under standard conditions, normally at a temperature of 23 ◦ C and a relative humidity of 50%. This does not take into account that many formaldehyde-based adhesives can decompose and release formaldehyde uncontrolled under extreme climatic conditions (high temperatures and humidity) (Murphy et al., 2013). The alternatives to formaldehyde-based adhesives are limited, especially in the field of wood-based materials. Currently diisocyanates are the only formaldehyde-free adhesives with any significance on the market. Wood-based materials made with 4.4 -diphenylmethandiisocyanate (MDI) later release practically no monomer MDI. However, the handling of diisocyanates during the manufacturing process is generally more demanding for the producer to protect workers from adverse health effects (Kenyon et al., 2012). Phenol–formaldehyde adhesives are chemically stable and
In summary, formaldehyde is definitely a “priority pollutant”, which deserves elevated but not exclusive attention. The substance is classified as an IARC Group 1 (or EU 1B) human carcinogen and is to be regulated accordingly. However, the measures being pressed by many authorities would seem uncoordinated, excessive and not consistently thought through. Building products and furnishings, as primary sources, are often over-regulated, while a lack of consideration of secondary sources and other factors somewhat negates the regulations’ effects. Also, some institutions are demanding unrealistically low guideline values for indoor spaces which, under the conditions of a modern industrial society, are hardly even possible in the outdoor air and are in many respects counter-productive. The formaldehyde emission guideline value proposed by Russia for certain building products can primarily be considered as a severe hurdle for trading. Regardless of this, there are no measurement methods available for routine use which allow for the determination of formaldehyde in air around or below 0.01 mg/m3 with a sufficient level of significance when considering the log-normal distribution of concentrations and analytical limitations (Salthammer, 2011). Therefore, such regulatory levels have little in common with responsible and consumer-friendly risk management. According to the currently available state-of-the-art and considering that formaldehyde is a threshold carcinogen, an orientation to the WHO guideline value of 0.1 mg/m3 would seem sensible, practicable and toxicologically defendable. Moreover, it can be used both for the assessment of indoor air and as a basis for emission assessment for building products. The argument is supported by Nielsen et al. (2013). These authors have evaluated current guideline approaches and come to the conclusion that the WHO guideline has been strengthened. It must be made clear that the WHO value is not to be exploited to a maximum, but that all efforts are to be made in accordance with the ALARA principle (as low as reasonably achievable) to stay as low below this value as possible. Acknowledgements The statements made in this publication are those of the author and are not necessarily in agreement with the views of governmental organizations, other research institutions or industry. This work has not been supported by any public or private funds. References Ad hoc, A.G., 2006. Krebserzeugende Wirkung von Formaldehyd – Änderung des Richtwertes für die Innenraumluft von 0.1 ppm nicht erforderlich. Umweltmed. Forsch. Prax. 11, 362. Corrêa, S.M., Arbilla, G., Martins, E.M., Quitério, S.L., de Souza Guimarães, C., Gatti, L.V., 2010. Five years of formaldehyde and acetaldehyde monitoring in the Rio de Janeiro downtown area – Brazil. Atmos. Environ. 44, 2302–2308. Duan, J., Tan, J., Yang, L., Wu, S., Hao, J., 2008. Concentration, sources and ozone formation potential of volatile organic compounds (VOCs) during ozone episode in Beijing. Atmos. Res. 88, 25–35. Gammage, R.B., Gupta, K.C., 1984. Formaldehyde. In: Walsh, P.J., Dudney, C.S., Copenhaver, E.D. (Eds.), Indoor Air Quality. CRC Press, Boca Raton, FL. Hedberg, E., Kristensson, A., Ohlsson, M., Johansson, C., Johansson, P.-Å., Swietlicki, E., Vesely, V., Wideqvist, U., Westerholm, R., 2002. Chemical and physical characterization of emissions from birch wood combustion in a wood stove. Atmos. Environ. 36, 4823–4837. International Agency for Research on Cancer (IARC), 2006. Formaldehyde, 2Butoxyethanol and 1-tert-Butoxy-2-Propanol. World Health Organization, Lyon, France.
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Institute of Medicine (IOM) of the National Academies, 2011. Climate Change, the Indoor Environment, and Health. The National Academies Press, Washington, DC. Jacobson, M.Z., 2012. Air Pollution and Global Warming. Cambridge University Press, New York, NY. Kenyon, N., Morrissey, B., Schivo, M., Albertson, T., 2012. Occupational asthma. Clin. Rev. Allergy Immunol. 43, 3–13. Murphy, M.W., Lando, J.F., Kieszak, S.M., Sutter, M.E., Noonan, G.P., Brunkard, J.M., McGeehin, M.A., 2013. Formaldehyde levels in FEMA-supplied travel trailers, park models, and mobile homes in Louisiana and Mississippi. Indoor Air 23, 134–141. Na, K., Cocker, D.R., 2008. Fine organic particle, formaldehyde, acetaldehyde concentrations under and after the influence of fire activity in the atmosphere of Riverside, California. Environ. Res. 108, 7–14. National Research Council, 2011. Review of the Environmental Protection Agency’s Draft IRIS Assessment of Formaldehyde. The National Academies Press, Washington, DC. Nielsen, G., Wolkoff, P., 2010. Cancer effects of formaldehyde: a proposal for an indoor air guideline value. Arch. Toxicol. 84, 423–446. Nielsen, G.D., Larsen, S.T., Wolkoff, P., 2013. Recent trend in risk assessment of formaldehyde exposures from indoor air. Arch. Toxicol. 87, 73–98. Pang, X., Mu, Y., Yuan, J., He, H., 2008. Carbonyls emission from ethanol-blended gasoline and biodiesel–ethanol–diesel used in engines. Atmos. Environ. 42, 1349–1358. Perera, F., Petito, C., 1983. Formaldehyde: a question of cancer policy? Science 216, 1285–1291.
Salthammer, T., 2011. Critical evaluation of approaches in setting indoor air quality guidelines and reference values. Chemosphere 82, 1507–1517. Salthammer, T., 2013. Formaldehyde in the ambient atmosphere: from an indoor pollutant to an outdoor pollutant? Angew. Chem. Int. Ed. 52, 3320–3327. Salthammer, T., Bahadir, M., 2009. Occurrence, dynamics and reactions of organic pollutants in the indoor environment. CLEAN: Soil Air Water 37, 417–435. Salthammer, T., Mentese, S., Marutzky, R., 2010. Formaldehyde in the indoor environment. Chem. Rev. 110, 2536–2572. Sarathy, S.M., Oßwald, P., Hansen, N., Kohse-Höinghaus, K., 2014. Alcohol combustion chemistry. Prog. Energy Combust. Sci. 44, 40–102. Schripp, T., Salthammer, T., Wientzek, S., Wensing, M., 2014. Chamber studies on nonvented decorative fireplaces using liquid or gelled ethanol fuel. Environ. Sci. Technol. 48, 3583–3590. Spengler, J.D., Sexton, K., 1983. Indoor air pollution: a public health perspective. Science 221, 9–17. Wolkoff, P., Nielsen, G.D., 2010. Non-cancer effects of formaldehyde and relevance for setting an indoor air guideline. Environ. Int. 36, 788–799. World Health Organization, 1983. Indoor Air Pollutants – Exposure and Health Effects. EURO Reports and Studies, Copenhagen. World Health Organization, 1987. Air Quality Guidelines for Europe. WHO Regional Office for Europe, Copenhagen. World Health Organization, 2010. WHO Guidelines for Indoor Air Quality: Selected Pollutants. WHO Regional Office for Europe, Copenhagen.
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ARTICLE IN PRESS International Journal of Hygiene and Environmental Health xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
International Journal of Hygiene and Environmental Health journal homepage: www.elsevier.com/locate/ijheh
Commentary
The formaldehyde dilemma Tunga Salthammer ∗ Fraunhofer WKI, Department of Material Analysis and Indoor Chemistry, Bienroder Weg 54 E, 38108 Braunschweig, Germany
a r t i c l e
i n f o
Article history: Received 11 February 2015 Received in revised form 23 February 2015 Accepted 23 February 2015 Keywords: Formaldehyde Guideline values Legislation Building products Secondary sources Indoor/outdoor
a b s t r a c t The IARC’s 2004 classification of formaldehyde as a human carcinogen has led to intensive discussion on scientific and regulatory levels. In June 2014, the European Union followed and classified formaldehyde as a cause of cancer. This automatically triggers consequences in terms of emission minimization and the health-related assessment of building and consumer products. On the other hand, authorities are demanding and authorizing technologies and products which can release significant quantities of formaldehyde into the atmosphere. In the outdoor environment, this particularly applies to combusting fuels. The formation of formaldehyde through photochemical smog has also been a recognized problem for years. Indoors there are various processes which can contribute to increased formaldehyde concentrations. Overall, legislation faces a dilemma: primary sources are often over-regulated while a lack of consideration of secondary sources negates the regulations’ effects. © 2015 Elsevier GmbH. All rights reserved.
Introduction Formaldehyde, first synthesized in 1855, is a highly important base chemical with a worldwide production of over 21 million tons. The majority is sold as an aqueous solution (37%). Industrial applications range from resins and adhesives for wood-based materials and fiber insulation through to textiles, biocides, paper and even cosmetics (Salthammer et al., 2010). In the early 1980s, discussions began regarding a possible regulation of the substance (Perera and Petito, 1983). In the early 80ies, Spengler and Sexton (1983) identified formaldehyde as one of the priority indoor air pollutants. One of the first indoor air guideline levels was set in Germany in 1977 as 0.1 ppm (= 0.125 mg/m3 under standard atmospheric conditions) (Salthammer, 2011). The World Health Organization (WHO) began in 1983 to treat formaldehyde as an indoor pollutant (World Health Organization, 1983) and in 1987 they published an indoor guideline level of 0.1 mg/m3 (0.08 ppm) (World Health Organization, 1987). The International Agency for Research on Cancer (IARC) classified formaldehyde as a human carcinogen (Group 1) in 2004 (International Agency for Research on Cancer, 2006). The German Ad hoc Working Group confirmed the German indoor guideline level of 0.1 ppm in 2006 as a safe concentration as regards the carcinogenic effect of formaldehyde in the human organism (Ad hoc, 2006). The assessment is based on formaldehyde being a threshold carcinogen, meaning that under a certain threshold,
∗ Tel.: +49 531 2155 213; fax: +49 531 2155 808. E-mail address: [email protected]
the risk is negligible. The WHO also confirmed their guideline value for formaldehyde as 0.1 mg/m3 in the year 2010 (World Health Organization, 2010). Wolkoff and Nielsen (2010) investigated the WHO assessment thoroughly and considered an air quality formaldehyde guideline of 0.1 mg/m3 to be protective against both acute and chronic sensory irritation in the airways in the general population. Moreover, the same authors state that the formaldehyde WHO guideline value is also considered defendable for prevention of all types of cancer, including lymphohematopoietic malignancies (Nielsen and Wolkoff, 2010). In the United States, the Office of Environmental Health Hazard Assessment (OEHHA) Reference Exposure Limits (REL) are defined as 3 g/m3 (chronic) to 94 g/m3 (acute, 1 h). No Reference Concentration for Chronic Inhalation Exposure (RfC) is currently defined by the US EPA (National Research Council, 2011). The European Commission classified formaldehyde as a 1B carcinogen and mutagen 2 on June 5th, 2014 in the ordinance EU 605/2014. Category 1B states that the carcinogenic effect has been demonstrated in animal trials and is probable for humans. The reclassification results in a series of consequences depending on national legislation. For example in Germany, the sum of carcinogenic substances in the exhaust air from industrial plants is limited to a mass concentration of 1 mg/m3 . Until now, formaldehyde has belonged to the category of organic substances with a total sum value of 20 mg/m3 . Over the years, a number of national authorities reassessed their indoor air guideline values and subsequently intend to agree with the WHO recommendation of 0.1 mg/m3 . This harmonization is a pragmatic step as the WHO value is very well assessed and justified. Moreover, the guideline
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Fig. 1. Regulated and non-regulated outdoor and indoor formaldehyde sources.
value is also not normally restrictive as formaldehyde conditions in normal living conditions tend to average between 0.02 and 0.04 mg/m3 (Salthammer et al., 2010). However, some countries have introduced guideline values for formaldehyde which are considerably below the WHO recommendation (Salthammer, 2011). Discussion Formaldehyde has actually always been a topic of environmental policy discussions as an air-polluting substance which primarily enters the body through respiration. Demands for particularly low guideline and limit values regularly arise and these arguments are often based on preventative aspects rather than toxicological and epidemiological factors. Currently the lowest guideline value is 10 g/m3 in France and is defined as a long-term exposure of >1 year. Nielsen et al. (2013) have comprehensively discussed the French approach and do not consider it as a reliable alternative to the WHO guideline. Product authorization is also seeing a tendency toward ever-stricter regulation. In 2014, Russia proposed a limit of 0.01 mg/m3 for furniture, measured under standardized conditions in the air of a test chamber. Although the demands for comprehensive consumer protection are of course to be welcomed, guideline and limit values which go way beyond the toxicologically justified necessity are not automatically to be considered positive. In addition, attempts to achieve lower indoor air concentrations are normally conducted by placing tighter limits on emissions from products. This, however, is a rather short-sighted approach, as the resulting indoor air concentrations are always a function of the climatic parameters and the living conditions. A good example of this is pre-fabricated houses. These are often made from wood-based materials using formaldehyde-based adhesives. Although the release of formaldehyde from wood-based materials has been significantly reduced on the manufacturing side in recent years, the indoor air concentrations in pre-fabricated houses have not decreased by the same amount (Salthammer et al., 2010). This is generally considered to be because the average air exchange rates have simultaneously been significantly reduced due to heat insulation. Formaldehyde concentrations and air exchange rates are inversely correlated (Institute of Medicine, 2011). The finding is not new and was already published more than 30 years ago by Gammage and Gupta (1984). Today, legislation on energy saving requires a certain air-tightness for living space, which often contradicts the need for sufficient natural air exchange. The operation of ventilation equipment with filtration systems is a possible alternative, but the energy consumption considerably increases as
target concentrations are reduced. This gives rise to the question of whether the technical effort required to minimize emissions and to reduce indoor air concentrations are always of corresponding benefit. This would certainly not seem to be the case when these target concentrations are excessively below well established guidelines. Another significant point concerns the plethora of unconsidered secondary sources of natural formaldehyde formation in indoor and outdoor space (see Fig. 1). Current legislation causes political developments for outdoor air to be diametrically opposed to administrative attempts to reduce formaldehyde concentrations in indoor air. On one hand this is caused by fuels and, especially, the increasing introduction of biofuels. Regardless of the undisputed need for sustainable fuels, this significant outdoor source of formaldehyde is thus being knowingly or unknowingly demanded or at least tolerated. The possible effects of fuel combustion on the formaldehyde concentration in the outdoor air are very well documented. As early as the 90s, i.e. during the introduction phase of biofuels, formaldehyde concentrations of over 100 g/m3 were measured in the air of Brazilian cities (Corrêa et al., 2010). Under practical conditions, combustion processes are never complete, so byproducts (especially with various carbonyl compounds) are always to be reckoned with (Sarathy et al., 2014). The effect of ethanol fuel blends on air pollution as well as the emission of formaldehyde from passenger cars has also been discussed by Jacobson (2012). According to a study by Pang et al. (2008), 62–161 mg of formaldehyde per kW engine performance and hour are released when combusting diesel and biodiesel–ethanol–diesel. These mass levels are considerable in their sum, but have so far hardly been taken into account. Industrial plants, however, are faced with strict emission reduction requirements. Forest fires are also a known natural formaldehyde source, but are difficult to characterize due to their uncontrolled conditions (Na and Cocker, 2008). During controlled combustion of wood in appropriate stoves for heating, around 200–1000 mg of formaldehyde are released per kg of wood depending on the type of wood and combustion process (Hedberg et al., 2002). A situation which can, at best, be described as inconsistent concerns indoor air. Decorative ethanol fires are subject to no significant admission procedure, but can cause extremely high formaldehyde concentrations under normal living conditions (Schripp et al., 2014). With the increasing pollution of the outdoor air with organic substances, photochemical reactions have established themselves as a significant source of formaldehyde. The ozonoloysis and the reactions of alkanes and alkenes with hydroxyl radicals and nitrous oxides are well known and have been described in detail. Photochemical smog as a
Please cite this article in press as: Salthammer, T., The formaldehyde dilemma. Int. J. Hyg. Environ. Health (2015), http://dx.doi.org/10.1016/j.ijheh.2015.02.005
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later emit lower formaldehyde quantities than urea–formaldehyde adhesives, but may release traces of phenol. With all substitutes for formaldehyde there is the question of their health benefit, their cost-effectiveness and their overall ecological balance. Concluding remarks
Fig. 2. Range of formaldehyde concentrations in indoor and outdoor air. The range of current indoor guideline values between 8 ppb and 100 ppb is also provided. Reprinted from Salthammer (2013) with permission from John Wiley & Sons, Inc.
formaldehyde source is, especially in polluted megacities, a growing problem (Duan et al., 2008). Chemical reactions which lead to the formation of formaldehyde also take place indoors, despite the lack of the typical day/night atmospheric chemistry, but these are only controllable to a limited extent. The sources are normally terpene/ozone reactions or photocatalytic processes (Salthammer and Bahadir, 2009). When considering the facts discussed, it becomes clear that the political measures to limit formaldehyde (regardless of whether on the national or international level) currently face a dilemma. On one hand great efforts are being made to politically impose ever-lower formaldehyde limits on building product emissions and indoor air concentrations. Some of these are hardly justifiable from a prevention point of view and definitely not justifiable from a toxicological point of view. On the other hand one can observe a certain ambivalence, as secondary sources in indoor and outdoor spaces – and the influence of building and construction – generally remain unconsidered. Indoor formaldehyde concentrations are tending to fall, but outdoor concentrations are tending to rise. As pointed out earlier (Salthammer, 2013), this will eventually lead to the absurd situation that under certain conditions (e.g. in large cities with high air pollution) the formaldehyde concentration in the outdoor air will be higher than in the indoor air (see Fig. 2), which will then result in consequences for living and ventilation behavior. Stricter regulatory measures for building products can, in principle, further reduce the general population’s exposure to formaldehyde in indoor spaces. This is, however, generally already fairly below the WHO guideline value. Peak concentrations and high short-term exposure (e.g. by use of formaldehyde as a conservation agent in medical laboratories or by combusting ethanol or kerosene indoors) remain unaffected. Also, elevated formaldehyde concentrations such as those measured in the FEMA-supplied trailers following hurricane Katrina can only be minimized to a limited extent by emission restrictions. The emissions assessment of building products takes place under standard conditions, normally at a temperature of 23 ◦ C and a relative humidity of 50%. This does not take into account that many formaldehyde-based adhesives can decompose and release formaldehyde uncontrolled under extreme climatic conditions (high temperatures and humidity) (Murphy et al., 2013). The alternatives to formaldehyde-based adhesives are limited, especially in the field of wood-based materials. Currently diisocyanates are the only formaldehyde-free adhesives with any significance on the market. Wood-based materials made with 4.4 -diphenylmethandiisocyanate (MDI) later release practically no monomer MDI. However, the handling of diisocyanates during the manufacturing process is generally more demanding for the producer to protect workers from adverse health effects (Kenyon et al., 2012). Phenol–formaldehyde adhesives are chemically stable and
In summary, formaldehyde is definitely a “priority pollutant”, which deserves elevated but not exclusive attention. The substance is classified as an IARC Group 1 (or EU 1B) human carcinogen and is to be regulated accordingly. However, the measures being pressed by many authorities would seem uncoordinated, excessive and not consistently thought through. Building products and furnishings, as primary sources, are often over-regulated, while a lack of consideration of secondary sources and other factors somewhat negates the regulations’ effects. Also, some institutions are demanding unrealistically low guideline values for indoor spaces which, under the conditions of a modern industrial society, are hardly even possible in the outdoor air and are in many respects counter-productive. The formaldehyde emission guideline value proposed by Russia for certain building products can primarily be considered as a severe hurdle for trading. Regardless of this, there are no measurement methods available for routine use which allow for the determination of formaldehyde in air around or below 0.01 mg/m3 with a sufficient level of significance when considering the log-normal distribution of concentrations and analytical limitations (Salthammer, 2011). Therefore, such regulatory levels have little in common with responsible and consumer-friendly risk management. According to the currently available state-of-the-art and considering that formaldehyde is a threshold carcinogen, an orientation to the WHO guideline value of 0.1 mg/m3 would seem sensible, practicable and toxicologically defendable. Moreover, it can be used both for the assessment of indoor air and as a basis for emission assessment for building products. The argument is supported by Nielsen et al. (2013). These authors have evaluated current guideline approaches and come to the conclusion that the WHO guideline has been strengthened. It must be made clear that the WHO value is not to be exploited to a maximum, but that all efforts are to be made in accordance with the ALARA principle (as low as reasonably achievable) to stay as low below this value as possible. Acknowledgements The statements made in this publication are those of the author and are not necessarily in agreement with the views of governmental organizations, other research institutions or industry. This work has not been supported by any public or private funds. References Ad hoc, A.G., 2006. Krebserzeugende Wirkung von Formaldehyd – Änderung des Richtwertes für die Innenraumluft von 0.1 ppm nicht erforderlich. Umweltmed. Forsch. Prax. 11, 362. Corrêa, S.M., Arbilla, G., Martins, E.M., Quitério, S.L., de Souza Guimarães, C., Gatti, L.V., 2010. Five years of formaldehyde and acetaldehyde monitoring in the Rio de Janeiro downtown area – Brazil. Atmos. Environ. 44, 2302–2308. Duan, J., Tan, J., Yang, L., Wu, S., Hao, J., 2008. Concentration, sources and ozone formation potential of volatile organic compounds (VOCs) during ozone episode in Beijing. Atmos. Res. 88, 25–35. Gammage, R.B., Gupta, K.C., 1984. Formaldehyde. In: Walsh, P.J., Dudney, C.S., Copenhaver, E.D. (Eds.), Indoor Air Quality. CRC Press, Boca Raton, FL. Hedberg, E., Kristensson, A., Ohlsson, M., Johansson, C., Johansson, P.-Å., Swietlicki, E., Vesely, V., Wideqvist, U., Westerholm, R., 2002. Chemical and physical characterization of emissions from birch wood combustion in a wood stove. Atmos. Environ. 36, 4823–4837. International Agency for Research on Cancer (IARC), 2006. Formaldehyde, 2Butoxyethanol and 1-tert-Butoxy-2-Propanol. World Health Organization, Lyon, France.
Please cite this article in press as: Salthammer, T., The formaldehyde dilemma. Int. J. Hyg. Environ. Health (2015), http://dx.doi.org/10.1016/j.ijheh.2015.02.005
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Institute of Medicine (IOM) of the National Academies, 2011. Climate Change, the Indoor Environment, and Health. The National Academies Press, Washington, DC. Jacobson, M.Z., 2012. Air Pollution and Global Warming. Cambridge University Press, New York, NY. Kenyon, N., Morrissey, B., Schivo, M., Albertson, T., 2012. Occupational asthma. Clin. Rev. Allergy Immunol. 43, 3–13. Murphy, M.W., Lando, J.F., Kieszak, S.M., Sutter, M.E., Noonan, G.P., Brunkard, J.M., McGeehin, M.A., 2013. Formaldehyde levels in FEMA-supplied travel trailers, park models, and mobile homes in Louisiana and Mississippi. Indoor Air 23, 134–141. Na, K., Cocker, D.R., 2008. Fine organic particle, formaldehyde, acetaldehyde concentrations under and after the influence of fire activity in the atmosphere of Riverside, California. Environ. Res. 108, 7–14. National Research Council, 2011. Review of the Environmental Protection Agency’s Draft IRIS Assessment of Formaldehyde. The National Academies Press, Washington, DC. Nielsen, G., Wolkoff, P., 2010. Cancer effects of formaldehyde: a proposal for an indoor air guideline value. Arch. Toxicol. 84, 423–446. Nielsen, G.D., Larsen, S.T., Wolkoff, P., 2013. Recent trend in risk assessment of formaldehyde exposures from indoor air. Arch. Toxicol. 87, 73–98. Pang, X., Mu, Y., Yuan, J., He, H., 2008. Carbonyls emission from ethanol-blended gasoline and biodiesel–ethanol–diesel used in engines. Atmos. Environ. 42, 1349–1358. Perera, F., Petito, C., 1983. Formaldehyde: a question of cancer policy? Science 216, 1285–1291.
Salthammer, T., 2011. Critical evaluation of approaches in setting indoor air quality guidelines and reference values. Chemosphere 82, 1507–1517. Salthammer, T., 2013. Formaldehyde in the ambient atmosphere: from an indoor pollutant to an outdoor pollutant? Angew. Chem. Int. Ed. 52, 3320–3327. Salthammer, T., Bahadir, M., 2009. Occurrence, dynamics and reactions of organic pollutants in the indoor environment. CLEAN: Soil Air Water 37, 417–435. Salthammer, T., Mentese, S., Marutzky, R., 2010. Formaldehyde in the indoor environment. Chem. Rev. 110, 2536–2572. Sarathy, S.M., Oßwald, P., Hansen, N., Kohse-Höinghaus, K., 2014. Alcohol combustion chemistry. Prog. Energy Combust. Sci. 44, 40–102. Schripp, T., Salthammer, T., Wientzek, S., Wensing, M., 2014. Chamber studies on nonvented decorative fireplaces using liquid or gelled ethanol fuel. Environ. Sci. Technol. 48, 3583–3590. Spengler, J.D., Sexton, K., 1983. Indoor air pollution: a public health perspective. Science 221, 9–17. Wolkoff, P., Nielsen, G.D., 2010. Non-cancer effects of formaldehyde and relevance for setting an indoor air guideline. Environ. Int. 36, 788–799. World Health Organization, 1983. Indoor Air Pollutants – Exposure and Health Effects. EURO Reports and Studies, Copenhagen. World Health Organization, 1987. Air Quality Guidelines for Europe. WHO Regional Office for Europe, Copenhagen. World Health Organization, 2010. WHO Guidelines for Indoor Air Quality: Selected Pollutants. WHO Regional Office for Europe, Copenhagen.
Please cite this article in press as: Salthammer, T., The formaldehyde dilemma. Int. J. Hyg. Environ. Health (2015), http://dx.doi.org/10.1016/j.ijheh.2015.02.005
