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PVC: Outgassing or In-Home Poisoning

It's one of the most hazardous consumer products ever created.  It’s dangerous to human health and the environment at every stage of its lifecycle: from production, to use, to disposal, yet it’s the most widely used material on earth. Beware of PVC, the Poison Plastic.

Did you know: Most plastics are made from petroleum (oil or natural gas) and plastics can contain a whole host of chemical additives that are never labelled that can be toxic to animals and humans.  PVC is one such toxin-laden plastic.

The additives are not chemically bonded to the PVC polymer but are merely mixed into the plastic during its formulation. Over time, they leach out of vinyl products, entering the air, water or other liquids with which the product comes in contact.

Studies show that some toxins in plastics are building up in humans and that some of us may be experiencing serious health effects as a result.  

Besides that, toxic manufacturing byproducts like dioxin (the most potent carcinogen known to science), hydrochloric acid and vinyl chloride are unavoidably created in the production of PVC and can cause severe health problems like cancer, endometriosis, neurological damage, immune system damage, respiratory problems, liver and kidney failure, and birth defects.

The chemical substances produced by PVC during its entire lifecycle are already present in global, local, and workplace environments at unacceptably high levels. Yet there is little public awareness of its adverse health and environmental effects.

PVC is an unnecessary toxic plastic. Although found in a wide variety of products from food packaging to children’s toys, plumbing and building materials to medical devices in every case alternatives to it exist.

Here’s what you should know about PVC, a largely unrealized public health menace.

PVC: The Poison Plastic

Ever wondered why your new car; plastic shower cap, curtain or tote bag; or your baby’s new toy has an offensive smell for days, even months?  There’s more to that “new” smell than you think.  That whiff of bad air you get is from PVC (polyvinyl chloride) — one of the most hazardous consumer products ever created on earth which is present in these and many other consumer products we use daily.

PVC products stink because they contain volatile organic compounds (VOCs). These are poisonous carbon-containing chemicals that are volatile enough to evaporate at room temperature. This process, called outgassing, is also a problem with building products such as plywood, particleboard, carpet and pads, paints, stains and glues.

Outgassing odors are most noticeable when products are new, but diminish over time until they finally disappear. A shower curtain can outgas for a month or longer, for example, depending on conditions. High temperature and humidity will speed up the release of VOCs.

VOCs can be toxic. Most commonly they irritate eyes, noses and throats, causing coughing, headaches, dizziness and nausea. The symptoms go away when outgassing ceases.

But the danger doesn’t stop there.  Did you know: From the time it is manufactured right up to its disposal, PVC keeps on releasing dangerous chemicals that can cause cancer, making it the worst plastic for our health and the environment.

What is PVC?

Polyvinyl chloride, commonly known as PVC or vinyl, is one of the most common synthetic materials. It’s widely used in construction materials (eg: pipes and fittings, windows, flooring, fencing, decking, roofing, wall coverings, wire and cable products), transport and packaging materials, medical supplies, and consumer products (eg: credit cards and toys).

PVC use has grown rapidly since World War II, when it gained popularity as a rubber substitute.  PVC is presently the second most widely used plastic in the world. And it’s one of today’s most dangerous toxic offenders. It cannot be recycled, and it is considered by many experts to be the most dangerous, carcinogenic plastic ever created by man.

Why PVC is Dangerous

PVC is dangerous to human health and the environment throughout its entire life cycle — at the factory, in our homes, and in the trash.? Its manufacture, product life and disposal all pose great environmental and health hazards.

The dangers of PVC are from the persistent pollutants it releases and the toxic additives used to produce PVC products.

What it contains: PVC is the only common plastic that contains chlorine. Although the plastics industry likes to point out that chlorine comes from ordinary salt, chlorine is actually listed by the US federal government as an “extremely hazardous substance”. Vinyl chloride, the building block of PVC, can cause cancer in humans, according to the US government’s National Toxicology Program.

PVC products also often contain dangerous toxic additives such as mercury, dioxins, lead and phthalates (used as softeners) which can leach out and pose dangers to consumers.

Lead, for example, can damage the brain and nervous system and cause behavior, learning and developmental disabilities.

Phthalates are additives widely used in the production of PVC to make it soft and flexible. Phthalates have been associated with an increased risk of cancer and kidney and liver damage.

Exposure to phthalates has also been linked with premature births, early puberty in girls, impaired sperm quality and sperm damage in men, genital defects, and reduced testosterone production in boys.

Many of the chemicals are thought to interfere with the reproductive system and development.

When produced or burned, PVC plastic releases dioxins, a group of the most potent synthetic chemicals ever tested, which can cause cancer (dioxin is the most potent carcinogen known to science) and harm the immune and reproductive systems.

Dioxins are extremely long-lived in the environment, and, because they are fat-soluble, they concentrate in the tissues of humans and other species.

When used, PVC products pose health risks.  Many of the toxic additives in PVC can be released from PVC products when they are used or handled by consumers. PVC products also release toxic fumes if they catch fire.

The vast majority of PVC manufactured is used in the production of building materials, however it’s also used in many other consumer products such as children’s toys, baby’s shampoo bottles, office supplies and packaging and thousands of other products, including medical products.

PVC harms all who come in contact with it — from workers making the products, communities located near PVC manufacturing plants, and consumers purchasing them, and to those living near landfills and incinerators where the products are discarded.

PVC uses and releases highly hazardous chemicals including vinyl chloride, dioxins, mercury, phthalates, and other chemicals that have been linked to deterioration of the central nervous system, liver damage, reproductive harm, and certain cancers.

Off-Gassing: An Invisible Threat

I don't know of a consistent authoritative name for off-gassing. This is why I listed out-gassing, outgassing, off-gassing and offgassing in the title. At the time this article was written there was a Wikipedia post on the subject, but it appears currently appears unprofessional and not authoritative. I spoke with an engineer on the subject, and he used the term off-gassing.

Off-gassing of harmful chemicals from various sources inside our homes has become a subject of concern for informed consumers. Although there are many potential sources for harmful off-gassing, mattresses and pillows have become a point of focus. Although even the worst off-gassing mattress or pillow may only release trace amounts of chemicals, sleeping on the mattress in extreme close proximity for several hours a day may in some cases, cause severe negative health effects. Some consumers may wonder what off-gassing is and what the most common offending materials are.

Outgassing is the phenomena of materials decomposing and releasing particles into the surrounding air. Moisture, sealants, lubricants, solvents, softeners, plastics and adhesives are the most common sources of outgassing. Even refined metals and glass may outgass depending on impurities present in the materials.

Outgassing is only a problem in closed environments such as in a space shuttle, or in an area with no circulation. Even nearly odorless materials, such as wood, or a rock may create an odor if kept in a completely sealed box for months or years. Out-gassing only becomes a concern when harmful substances are released into our atmosphere which may negatively impact our health.

Common Off-Gassing Materials

Materials that outgass carcinogenic or otherwise harmful by-products are a concern for humans, especially for young children with developing minds and bodies, as well as pregnant women. The list of potentially harmful out-gassing materials, just in our homes is suprisingly long. Some examples of potential outgassing sources are paint, mattresses, furniture, air fresheners, paint-thinner, bleach, or flame retardants added to cloth or furniture.

Even the wood frameworks of most homes contain potential sources of harmful outgassing. For example, both Plywood and Oriented Strand Board (OSB) contain forms of formaldehyde, a substance which the EPA has classified as a probable carcinogen for humans. Some forms of insulation, insulation, and other construction materials may also produce harmful outgassing.

Victims of our Own Progress: Growing Economies and Rising Pollution

Out-gassing has become one of many rising concern among consumers worldwide, as people have begun to recognize new harmful effects of industrialization. In some ways, the modern world has become of victim of its own progress. Cheap, lightweight, strong, and durable materials often require plastics, polymers, and various chemicals to form. The materials are used much more heavily in industrialized nations, which to some extent may account for the higher per-capita cancer cases in these areas (aside from pesticides and genetically modified crops).

Often materials are used heavily before the health risks of cancer or disease are completely understood. For example, lead-based paint and asbestos were heavily used throughout the USA for many years, until it was slowly discovered that these materials had both debilitating and often deadly side effects. Although asbestos and lead-based paint were both banned, there are still many potentially harmful materials that surround us in our day-to-day lives. Some may argue that o-zone depletion, radiation, and other types of pollution are more to blame than chemicals or materials off-gassing, but these factors are beyond the scope of this article.

Air Pollution is Likely A Driving Force is Increasing Cancer Deaths Worldwide

The pollution of our environment appears to be causing an increase in the number of cancer cases worldwide. According to the World Health Organization, cancer (especially lung cancer) is a leading cause of death worldwide, and the number of cases worldwide are growing substantially. This is an excerpt from the WHO website: "The number of global cancer deaths is projected to increase 45% from 2007 to 2030 (from 7.9 million to 11.5 million deaths)... In most developed countries, cancer is the second largest cause of death after cardiovascular disease, and epidemiological evidence points to this trend emerging in the less developed world." (http://www.who.int/features/qa/15/en/index.html). It is clear the risk of cancer is substantially higher in developed countries, which are heavily producing carcinogenic byproducts due the net-effects of industrialized societies.

When thinking of the costs of industrialization and pollution, most people probably think of the industrial revolution, when the skies literally turned dark in heavy coal burning areas causing immediate and extreme harmful side effects. The byproducts of massive levels of coal-burning and fossil fuels released harmful chemicals, heavy metals, CO2 into the atmosphere causing severe and obvious health damage to those nearby.

The Hidden Cost of Industrialization

Ironically, completely undeveloped countries sometimes have longer life expectancies than people in first world countries. Perhaps living in a hut made with all natural materials and eating locally grown completely organic (and fiber rich) foods with no pesticides is somewhat under-rated. Although we have been able to create substantially cleaner environments with less bacteria, mold, and dust, and we have found ways to mass-produce cheap and often processed foods, these advancements have come with some deadly hidden health costs (cancer, heart disease, etc.). Perhaps we should not be surprised that there is in fact a price to pay (health risks) for our cheap, lightweight, durable chemical based materials, and pesticide filled foods upon which we have built our society.

Although current pollutants are perhaps less obvious than those during the days of the industrial revolution, they still pose deadly and to some extent, unknown future threats. Many of our present day pollutants are deadly, even though very few short term effects are clear: chemicals, pesticides, genetically modified foods, heavy metals and other toxins released into our environment all pose threats to our health. As technology advances, we have been able to identify these threats and begin to address them one by one.

Life is Priceless

The popular movement towards renewable energy, green construction, and organic products are based on our recognition that life itself is priceless and that the quality of our lives is profoundly effected by what we eat, drink, breath, and even where we sleep. For most of us, our scope of control is limited by our immediate homes, and families. As consumers there are many things we can do to improve the quality of our lives and improve our environment, even within the space of our own home. Often, choosing organic or environmentally friendly solutions are much more expensive on the surface. However, many consumers have started recognizing that often non-organic, non-environmentally friendly alternatives often have hidden costs which can't be expressed on a price tag.

Things we can do

For those of us who can afford environmentally friendly solutions, there are many things we can do in our homes and communities. When painting your home, you might consider using low VOC (Volatile Organic Compound Paints). When choosing the type of carpeting you will use, you may also look for organic, low outgassing carpets. We can change the way we eat; recent news reports have been citing studies which now conclude that diets which are heavy in animal proteins (meats) create an increased risk of cancer (aside from cardiovascular disease related risks). You can go to your dentist and get your amalgam fillings removed (a known source of mercury). You can also choose a organic mattresses and pillows made of natural materials that will not off-gass harmful chemicals.

Everything Counts

Although many 'experts' may claim that each of the above individual measures may have little or no effect, I would venture to say that the net effect of making many positive environmental changes is substantial. There are substantial number of very unhealthy people in our society which doctors cannot diagnose; and some people have found simply changing their diet or their mattress had profound positive effects on their health.

Mattress Off-Gassing has been the subject of several independent studies which now claim this is a primary cause for SIDs in children, as well as a cause of severe allergic reactions in some adults. Learn more about the carcinogenic flame retardants they are now adding to mattresses as well as a few solutions on how to protect yourself and your newborns.

Most of us who have lived or worked in a building that was re-roofed with tar, or passed by a road-crew installing asphalt are aware of the extremely pungent (smelly) odors emitted by bitumen. The noxious fumes you smell from tars being applied to roads or roofs are volatile organic compounds, emitted from these substances. Bitumen, asphalt and tars are based on crude oil waste. After the gasoline, kerosene, or other more volatile fuels are removed from crude oil, the leftovers can be converted to tar. Many roofs and most roads contain tars; so the question of whether or not these materials are toxic is perhaps an important one.

While researching the subject of asphalt and modified bitumen off-gassing, I found a severe lack of good, scientific, easily palatable materials. My goal was to find whether or not the fumes emitted by these materials are safe to breath. Most authoritative articles were very laborious and verbose for those of us who don't work daily in a laboratory. I have done my best to complete some solid groundwork and give an authoritative, and hopefully enlightening perspective on the subject of asphalt fumes.

What Makes Tar Roofs Smelly

Anyone who has worked with any form of Tar, including Asphalt, Coal Tar, or Modified Bitumen in any application is well aware of the oppressive odors these complex organic compounds release. When a home is re-roofed with a Built-up-Roof (BUR) (or any roof type that is based on tar), the coal tar or modified bitumen applied to seal the roof and make it watertight, off-gasses heavily for several weeks or months.

The heavy stench these roofs create are due to VOCs (volatile organic compounds) which are released into the atmosphere. Both coal tar and modified bitumen release high levels of polycyclic aromatic hydrocarbons (PAH), which are known carcinogens and have been reported to cause serious health complications in humans. Generally, these same VOCs also cause the pungent odors which assault the olfactory senses of anyone near recently built asphalt road or tar roof (Modified Bitumen, or Coal Tar).

How Modified Bitumen, Asphalt, and Coal Tar are Made

Although recent advances allow bitumen (or tar) to be made from corn, rice, or molasses, for most of the last 100 years, bitumen was made from the refinement of crude oil or coal. After more valuable (and more volatile) fuels such as gasoline, kerosene or diesel are removed, the left-over, and thick brown viscous material is known as bitumen.

Coal Tar Pitch

As far back as 5,000 BC, there are records of humans using 'pitch' (a form of tar or bitumen) based on tree resins. Bitumen is used as an essential binding element in many applications (such as asphalt) because it has excellent adhesive properties and takes an extremely long time to wear away. Bitumen is a semi-solid, although it is often heated to create a more viscous liquid material.

Bitumen (Tar) Applications

For example, in BUR roofing applications a giant kettle is heated to 200C or more to keep the bitumen in a semi-liquid state. After the tar is hot-mopped onto the roof, it cools back into a solid form, creating a waterproof seal. For roadway applications, crushed stone, sand, and gravel are mixed with the semi-solid bitumen to create solid Asphalt.

Caulkings based on asphalt are often used to repair leaks in boats and ships; in fact, this is one of the oldest uses of the material (pitch was used in ancient times to waterproof ships). Most of the roads and many jogging paths throughout the USA are made with Asphalt (a form of bitumen). Bitumen is also a key component in many roofing materials such as asphalt shingles and tar-paper.

Bitumen: Based on Fossil Fuels

Decayed plants, algae, bacteria and other organic matter collected in places, such as the ocean floor or other high pressure areas over 100 million years ago. Layers of sediment dirt, rock and mud covered and trapped the organic matter forcing anaerobic decay under increasing pressure and heat. Extremely mature, decayed materials, in oxygen deprived, high pressure, and high heat environments result in fossil fuels, such as coal, crude oil, or natural gas.

Since the whole process takes millions of years, fossil fuels are a limited resource and cannot easily be replaced. The most refined fossil fuels are also the most unstable and contain the highest levels of energy. Gasoline, a very pure form of fossil fuel (with very high concentrations of stored energy) is highly volatile and will explode when placed near a match. On the other hand, coal, a much less refined fossil fuel is less volatile, and contains less energy; thus explaining why coal only burns slowly when placed in an open flame.

Tars like modified bitumen and asphalt are based on further processing the sticky brown leftover waste after crude oil is refined. Depending on the application, tars must go through further refinement before they can be used as asphalt or bitumen for applications on roofing, ships or roads.

Health Impacts

The long term negative health impacts of fossil fuel burn-off is well documented and widely accepted. Generally, when fuel such as gasoline or diesel is burned, various byproducts are released into the atmosphere such as CO2, heavy metals, and various toxins. However, there are some fossil fuel based materials, such as Modified Bitumen and Asphalt which most government agencies remain undecided in terms of health impact for the general public; at least when in reference to already constructed roads and roofs. These materials are only considered 'possible' carcinogens for the general public.

In contrast, these same materials are known carcinogens for roof workers, or road construction workers. Just like paint thinner, solvents, or other volatile compounds which we are exposed to in our day to day lives, the level of health risks involved scale up with increased exposure levels.

Studies Conclude Bitumen is Carcinogenic

According to The National Institute for Occupational Safety and Health (NIOSH / CDC) "Studies of roofers [and workers with high exposure to modified bitumen or asphalt] show an excess of lung, bladder, brain, liver, and digestive system cancers". The CDC and other agencies maintain very conservative positions and will not officially declare these materials are carcinogenic unless the evidence is overwhelming.

For now, these tars remain 'suspected' carcinogens. Cigarettes provide an excellent example of the governments refusal to accept 'the writing on the wall'. For many years, studies showed a link between cigarette smoking and lung cancer, yet for decades the government refused to officially recognize this. Generally, by the time the government is willing to declare any product as harmful, the evidence is absolutely overwhelming and indisputable.

In defense of the government, its important we understand that they will not shut down a multi-billion dollar industry, and cause millions of Americans to lose jobs unless it is absolutely clear that industry is harming consumers and/or the environment. As a side note, consumers should not completely abdicate their own responsibilities to research purchasing decisions and come to their own conclusions. Even those who believe the government alone should tell us what is safe and what is not must realize that at least to some extent this is not practical.

Modified Bitumen is Less Carcinogenic Than Coal Tar

There are many sources which claim that modified bitumen is not carcinogenic (cancer causing), while in contrast, coal tar is widely accepted as carcinogenic. Some sources claim that the process of making modified bitumen, which is done at lower temperatures (less than 500C) does not release the same harmful byproducts into the material in contrast to tars made at higher temperatures. Various tars such as coal tars, lignite tars, wood tars, peat tars and oil shale tars are usually made at temperatures around 700C although there are high temperature variations made at 900 to 1300C.

Tars made at temperatures over 1000C, which have been subsequently tested on animals, are highly carcinogenic. Tars in general contain known cancer causing agents, and PAH is the worst: "At least 20 different powerful carcinogens have already been detected in tars and pitches. The most powerful carcinogens from among the polycyclic aromatic hydrocarbons [PAH] have been found in the case of compounds with 5 or more benzene rings" (G. Collin, et al).

Modified bitumen, like other tars contains Polycyclic aromatic hydrocarbons (PAH), although it appears to off-gas substantially less than coal tar. Although some sources claim the substance is completely benign, there is a substantial body of research which says otherwise. "Most concentrations of individual PAHs in roofing (232°C or 316°C) and all concentrations in paving (163°C, except for one sample at 221°C) asphalts, whole or fumes [contained] 10 ppm and 2 ppm, respectively." (ASPHALT FUMES LITERATURE REVIEW by NIOSH)

Studies show that PAH is present in modified bitumen, just as in other tars. The key difference is that modified bitumen contains substantially less mutagenic VOCs in contrast to coal tar. However, to say it is completely benign is to ignore the fact that polycyclic aromatic hydrocarbons are found in modified bitumen. Studies performed by Niemeier et al.[1988] and Sivak et al. [1989] showed that incidence of cancer in coal tar pitch applied to the skin of mice was 10 to 100 times more frequent than with asphalt based tars. In other words, various forms of tar have been tested and there is already clear evidence that modified bitumen has the same, but admittedly lower health risks verse other tars.

Modified Bitumen is Carcinogenic at High Exposure Levels

Although modified bitumen is substantially less carcinogenic than coal tar, it still contains polycyclic aromatic hydrocarbons (PAH). Several studies have reported carcinogenicity in mice following applications of laboratory-generated asphalt roofing fume condensates (Thayer et al., 1981; Niemeier et al., 1988; Sivak et al., 1989, 1997).

Both modified bitumen and asphalt off-gas substantially less VOCs than coal tar; enough so that the government agencies such as the CDC remain undecided and simply list these materials as 'possible carcinogens'. This is despite studies which show otherwise: "Experimental studies using animal and in vitro models indicate that condensates from asphalt fumes are genotoxic and can promote skin tumorigenesis [carcinogenic]" (Ma-C, et al.). Studies have shown that rats exposed to asphalt fumes through their skin, lungs, and stomach developed cancerous tumors in each of these respective areas.

Definitions

Carcinogenesis = Carcinogenesis (the creation of cancer), is the process by which normal cells are transformed into cancer cells.

Tumorigenesis = (oncology) Production of a new tumor or tumors

Occupational Hazards: Asphalt and Modified Bitumen

As stated earlier, for roof and road workers, the evidence is overwhelming; these materials are highly hazardous with long term exposures. Complications such as tumors, liver and lung problems are well documented for those who work with these hazardous materials daily. Although studies with laboratory animals decisively show that both asphalt and modified bitumen cause cancerous tumors at high dosage levels over short time periods, the government remains unconvinced the risk levels are high enough to merit banning these materials.

There are dissenting studies as well, which claim asphalt does not cause cancer (consider they're were also studies that claimed cigarette smoking was perfectly safe long term, which we know to be completely false). In one study, roofing asphalt applied dermally to mice was not decisively carcinogenic (Emmett et al., 1981). However, we must question the methodology used since this is an exception to the rule.

For example, several studies found asphalt fumes created carcinogenic responses in mice with just 10 days or less of heavy exposure to asphalt fumes: "Asphalt fume as well as the vapor and aerosol components of asphalt were determined to be immunosuppressive following respiratory and systemic exposure. (3.5 hours per day for up to 10 days)" (Diotte-NM, et al).

Further studies showed that asphalt fumes can create tumorigenesis and carcinogenesis: "These results demonstrate that exposure to road paving-like asphalt fumes is immunosuppressive through systemic, respiratory, and dermal routes of exposure in a murine model and raise concerns regarding the potential for adverse immunological effects." (Stacey E. Anderson, et al.) There are many other studies, perhaps thousands or more which show similar results. Here is yet another example: "The raw roofing asphalt and neat asphalt fumes induced carcinomas (local skin cancers) in 3 of 30 and 20 of 30 C3H/HeJ mice, respectively." (Wess-JA, et al).

Industry Response

Generally, the manufacturers and other purveyors of modified bitumen, asphalt, and other related substances claim what they use is 'different' from the materials used in the many studies performed. Their attempts to discredit the large existing body of research which indicates these materials are carcinogenic is simply by using blanket claims that the studies used the wrong materials.

I find this hard to believe, since the vast majority of bitumens in use today are based on the exact same material: refined crude oil. While there is truth in the statement that modified bitumen or asphalt emit less toxic fumes because they are refined at lower temperatures, to claim they are completely safe is simply not true.

Summary

Some people who have touched (skin absorption) or breathed mixtures of PAHs emitted from modified bitumen, and asphalt have developed various forms of cancer. The same bitumen substances caused cancer in laboratory animals by breathing (lung cancer), ingesting them with food (stomach cancer), or by absorption through the skin (skin cancer).

Modified bitumen, asphalt, coal tars and all related substances are made from refined crude oil and all emit substantial levels of polycyclic aromatic hydrocarbons (PAH), which are known carcinogens. Roofers and road workers both have a high risk of contracting cancer or other health problems when exposed to the PAHs emitted from asphalts and tars daily. For consumers, the risk levels are unclear, although it is safe to say the fumes emitted by off-gassing tars and bitumens are truly not good for your health.

References

1-Asphalt Fumes Hazard Recognition, Occupational Safety & Health Administration (OSHA)

2-Health Effects of Occupational Exposure to Asphalt, US Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 2001-110, (2000, December), 886 KB PDF, 150 pages

3-Reducing Worker Exposure to Asphalt Fumes from Roofing Kettles, DHHS (NIOSH) Publication No. 2007–115 February 2007

4-Agency for Toxic Substances and Disease Registry (ATSDR). 1995. Toxicological Profile for Polycyclic Aromatic Hydrocarbons (PAHs). Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service.

5-The humoral immune response of mice exposed to simulated road paving-like asphalt fumes, Stacey E. Anderson, Albert E. Munson, Seth Tomblyn, B. Meade, NicoleM. Diotte Journal of Immunotoxicology 2008, Vol. 5, No. 3, Pages 307-313 , DOI 10.1080/15376510802312407

6-Status of Worker Exposure to Asphalt Paving Fumes with the Use of Engineering Controls, R. Leroy Mickelsen, Stanley A. Shulman, Anthony J. Kriech, Linda V. Osborn, and Adam P. Redman, Environ. Sci. Technol., 2006, 40 (18), pp 5661–5667 DOI: 10.1021/es060547z August 2006

7-Physical and Chemical Characterization of Asphalt (Bitumen) Paving Exposures , Robert F. Herrick a; Michael D. McClean b; John D. Meeker c; Leonard Zwack a; Kevin Hanley d , Published in: journal Journal of Occupational and Environmental Hygiene, Volume 4, Issue S1 2007 , pages 209 - 216 January 2007

8-Characterization of Laboratory Simulated Road Paving-Like Asphalt by High-Performance Liquid Chromatography and Gas Chromatography-Mass Spectrometry , Brandon F. Law a; Samuel Stone a; David Frazer a; Paul D. Siegel a, Journal of Occupational and Environmental Hygiene, Volume 3, Issue 7 June 2006 , pages 343 - 350 June 2006

9-Exposure to asphalt fumes activates activator protein-1 through the phosphatidylinositol 3-Kinase/Akt signaling pathway in mouse epidermal cells Ma-C; Wang-J; Luo-J Source The Journal of Biological Chemistry 2003 Nov; 278(45):44265-44272

10-The latest method for monitoring PACs in asphalt fume Olsen-LD; Neumeister-CE; Dollberg-DD Tijdschrift voor Toegepaste Arbowetenschap 2004 May; (2)(Suppl):85

11-Asphalt (Bitumen). Concise International Chemical Assessment Document, Wess-JA; Olsen-LD; Sweeney-MH, Concise International Chemical Assessment Document (CICAD) No. 59. International Programme on Chemical Safety (IPCS), Geneva, Switzerland: World Health Organization, 2004 Jan; :1-50

12-Asphalt fume - induced immunosuppression in B6C3F1 female mice, Diotte-NM; Munson-AE; Tomblyn-S; Meade-BJ, Toxicologist 2001 Mar; 60(1):27

13-Niemeier RW, Thayer PS, Menzies KT, Von Thuna P, Moss CE, Burg J [1988]. A comparison of the skin carcinogenicity of condensed roofing asphalt and coal tar pitch fumes. In: Cooke M, Dennis AJ, eds. Polynuclear Aromatic Hydrocarbons: A Decade of Progress. Tenth International Symposium. Columbus, OH: Battelle Press, pp. 609-647.

14-Sivak A, Menzies K, Beltis K, Worthington J, Ross A, Latta R [1989]. Assessment of the co-carcinogenic promoting activity of asphalt fumes. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, Division of Biomedical and Behavioral Science. NIOSH Contract No. 200-83-2612, NTIS Publication No. PB-91-110-213.

15-Teer und Pech, G. Collin, M. Zander, Rutgerswerke AG in Ullmanns Enzyklopadie der Technischen Chemie, fourth edition, Weinheim, 1982, vol. 22, pp 411 to 455

Single component polyurethane-modified bitumen compositions

16-Tar fumes raise air quality concerns, University of Texas