By: Rosemary Stephen

I am amazed at how many countries are affected by groundwater contamination from Trichloroethylene C2HCl3 (TCE). This chemical is used worldwide as a solvent, and its foot print is felt in occupational and non-occupational settings alike. Recently, two cases of non-occupational exposure to Trichloroethylene caught my attention; one in Canada and one in the United States. Though published via two different media — television and web newspaper - each covered stories about people who were exposed to TCE by means of contaminated groundwater.
The first report was broadcast on 29 January 2009 during Enquète, a weekly show on the CBC French TV channel in Canada. This documentary discussed ‘Shannon’, a small town in Québec, Canada. Residents of Shannon pump their water from private wells located on their own properties as the municipality does not have a public water system. They share the same aquifer as CFB Valcartier, a Canadian Forces Military Base. In 2000, the residents of the small town became aware that the water they were drinking was contaminated with TCE. Currently, within the population of Shannon, there is a high incidence of cancers — colon, prostate, kidney, brain and skin - possibly linked to this TCE exposure [1].
The second case was published in Cascade Connection web site on 28 Jan 2009 (http://connectionnewspapers.com/). This case involves TCE groundwater contamination in Sterling, Loudoun County Health Department Virginia USA. This was traced to an abandoned landfill; TCE migrated from the landfill to residential wells within a 1 mile (1.61km) radius. There was also a strong possibility that TCE vapours may have penetrated homes through cracks in basements or in crawl spaces. Currently, within the population of Sterling, information on any possible link between cancer and TCE exposure is lacking due to the very small number of people exposed and the strong possibility that other contaminants may also be present in the ground water [2].”
Case Study: Shannon, Province of Québec, Canada
Prior to 1980, SNC Lavalin, CFB Valcartier R&D and the Military Research Centre used TCE extensively. When the TCE lost its effectiveness through repeated use and could no longer be used as a degreaser, it was dumped into open, man-made lagoons to allow the TCE to evaporate (e.g. Lagoon C and Sector 214) [3]. Over time, TCE seeped from the lagoons, percolating through the sandy, porous soil of the area and contaminated the aquifer [4]. In 1997, base officials became aware that TCE had contaminated the aquifer serving the base and had migrated, contaminating private wells used by the community of Shannon [5]. Residents from Shannon, however, only became aware of the contamination in 2000, after water samples from one private well identified the presence of a chemical (TCE) registering 200 times above accepted safe levels [6]. Québec Public Health officials immediately took emergency measures; they told the residents to drink only bottled water and to shower with their windows open. In 2002, the Military also responded to the problem by drilling another well, but this new well only serviced about one third of Shannon’s homes. The residents, however, were outraged at the contamination and no longer trusted the base; they wanted an independent water source that was not connected to the base [7, 8].
In 2002, CFB Valcartier connected Shannon to a new, closely monitored well located on base property. Unfortunatly, it only served a third of the population of Shannon. In 2004, the town of Shannon successfully sued the Canadian Government and the Department of National Defense and received $19 million settlement. The residents, still distrustful of the Military, decided to use this money to find an independent water source not under military control. So far, Shannon has not been successful as exploratory wells failed to find a source of potable water that met the Canadian Water Standards. Very recently, however, (March 26 2009), the Canadian Government announced the provision of more than 13 million dollars to complete a water supply system for the municipality [9].
It is not known if any of the military personnel stationed on the Base prior to 1997 suffer from increased rates of cancers, but residents of Shannon who once lived, and who are currently living in 55 homes located within the most contaminated area — the ” Red Triangle”– suffer from a high incidence of cancer [10]. Residents named TCE as the cause of their high cancer rates, and they want compensation; a group of them have launched a class-action lawsuit against the Canadian government as well as against a subsidiary of SNC-Lavalin Group Inc. that owned the property where the TCE was used in an ammunition factory.
Case Study: Sterling, Loudoun County, Virginia, USA
In Sterling, the source TCE contamination was traced to an abandoned landfill called Hidden Lane. This landfill was in operation from 1971 through 1984 when it was then closed by the county of Loudoun for multiple violations of the zoning ordinance. In March 2008, Hidden Lane was designated a ‘Superfund site’ and put on the National Priorities list. Under the Comprehensive Environmental Response, Compensation, and Liabilities Act of 1980, a site becomes eligible for ‘Superfund’ when abandoned hazardous wastes represent a potential health risk to human population.
In 1988, Loudoun County Department of Health and the EPA started studies on the land fill, testing for hazardous substances. In three residential wells located close to the landfill, they found traces of TCE, its biodegradation products (see below for a list) and pesticides. In 2005, Loudoun County Health Department carried out testing on 68 more wells in the area of the landfill. Forty-five wells tested positive for TCE; 17 of these wells contained concentrations of TCE above the maximum contaminant level (MCL) of 5 micrograms per liter (mcg/L) while 28 other wells contained TCE, but below the MCL. Three years ago, the Agency for Toxic Substances and Disease Registry (ATSDR) visited the site and recommended that a proper filtration system be installed in homes which had contaminated wells. They selected carbon filters because they have the ability to separate TCE from water. These were installed by the Virginia Department of Environmental Quality (DEQ) and are maintained semiannually to ensure they function properly [11].
There is, however, also a possibility that vapor may seep into homes when the levels of volotile organic compounds (VOCs) are high in groundwater. Evaporation may take place through the soil above the water table or when the groundwater itself is in close proximity to the surface. There is, hence, no guarantee that homes in the vicinity of the contaminated site are still in good condition; TCE vapor may be entering the homes through cracks in the basement or through crawl spaces. This vapor can accumulate in living quarters; it will reach concentration levels above the 1.0 micrograms per cubic metre, the maximum for vapor concentration indoors set by EPA, unless windows are open [12]. Since the Hidden Valley landfill is now part of the Superfund List, the ATSDR felt that a well-defined health risks assessment was required to determine if vapor intrusion was indeed present inside 26 homes located closed to the landfill area. If this was the case, the ATSDR would request that the EPA take appropriate action through remediation [13]. This can be achieved by installing an abatement system similar to that for radon affected homes, which creates a negative pressure beneath the building slab and exhausts the TCE vapours to the outside [14].
The County Health Department has not confirmed if any residents have been affected directly by water contaminated with TCE, but because filtration systems were installed three years ago, the County Health department did not pursue medical testing [15].
What is Trichloroethylene?
Trichloroethylene is a man made, liquid chemical that is nonflammable, colorless with a sweet odor, belonging to the family of chlorinated volatile organic compounds (VOCs). It is widely used as an industrial solvent in military, commercial, and industrial applications. TCE is present in consumer products such as spot and paint remover, adhesives, type writer correction fluid and rug cleaning fluids [16] and it has been identified as a groundwater contaminant coming from numerous hazardous waste dumps and industrial sites [17]. It is among the most frequently detected organic contaminants in groundwater at waste sites in the USA, Japan, Canada, Europe and Australia [18].
According to the World Health Organisation (WHO), TCE is also present in the air we breath. In 2000, concentrations of TCE measured in urban areas worldwide showed background levels between <17 and 109 ng/m3 (actual guidelines recommend 5 ng/m3) [19]. In rural areas, levels between 0.10 and 0.68 μg/m3 have been reported [20]. Basically, we all inhale a certain amount of TCE and there is little we can do to avoid it. Peter Montague [21] says it very well when he wrote ” we industrial humans have managed to spread TCE everywhere”
The International Agency for Research on Cancer (IARC) considers Trichloroethylene a Group 2A carcinogen meaning that it has the potential of causing cancer in humans [22].
How humans are exposed to TCE
Activities such as drinking water (ingestion), swimming (ingestion and dermal absorption), showering (inhalation and dermal absorption) and handling contaminated soil (dermal absorption) are cited as the most frequent sources of exposure in non-occupational settings. In a domestic setting, long, hot showers allows TCE to volatilize from the hot water into the air. TCE will then accumulate and circulate easily inside the home especially if the home is well insulated [23]. In foods, TCE is believed to come from contaminated water used in food processing or from food processing equipment cleaned with TCE. In occupational settings, workers are exposed to TCE either through metal degreasing or via Tetrachloroethylene (PCE) or perchloroethylene (Perc) when working in a dry cleaning facilities.
How TCE behaves in the environment
In the past, no one considered the consequences of dumping TCE into the environment. No regulations existed prior to 1989 in the United States and prior to 1995 in Canada [24] to control dumping and use. Trichloroethylene does not affect the ozone layer, is not directly responsible for acid rain [25], and there is also no current data to suggest TCE affects the climate [26] but in 2001, the World Health Organization recognized the large distribution of TCE in surface water, rainwater and wells (bore water) [27].
In the atmosphere, the estimated half-life for trichloroethylene depends upon latitude, season and the concentration of photochemically produced hydroxyl radicals. These hydroxyl radicals will break down TCE into phosgene, dichloroacetyl chloride, formyl chloride and other degradation products in 6 to 40 days. Eventually, these sub-products create hydrochloric acid, a component of acid rain [28, 29, 30]. In Canada, the TCE atmospheric half-life during summer months ranges from 1 day in the south to 3 days in the north In winter, this reaction can extend to approximately 2 1/2 weeks in the south, to several months in the far north. TCE can move short to medium distances in the atmosphere depending on the wind speed and cloud cover [31]. In surface water the TCE half-life may take days to weeks to break down. It takes 11 days for TCE to volatize from a pond, 4-12 days to volatize from a lake and 1-12 days to volatize from a river. Particles of TCE may be found in bottom sediments in standing water if the organic content of the sediment is high.
How TCE contaminates groundwater
A large part of Trichloroethylene will volatilize in the air, but a small quantity will break down in the soil. TCE has the particularity of percolating unaltered into underground water and, being heavier than water, will sink below the groundwater strata. This behavior creates pools of contaminant which will be released over time. When released, TCE will eventually dissolve and spread as a plume, initially narrow and concentrated at its origin then spreading out further away from the source of contamination and decreasing in concentration. As it spreads in water, TCE will slowly evaporate. Through the activity of anaerobic bacteria, biodegradation will break down TCE into three sub products: 1,1,1-tricholorethane (DCA), 1,2-dichloroethene.(DCE), and vinyl chloride (VC) [32, 33].VC is considered to be more toxic than TCE and it should be investigated whenever TCE is present. Biodegradation will occur in an half life of months to years [34].
TCE will be present as a groundwater contaminant for decades unless adequate remediation is done [35]. The size of the contamination plume can be quite extensive, spreading under buildings and surface water. In 2001, the Shannon TCE plume was estimated between 4.5 to 5 km long (2.8 to 3.10 miles) by 650 m wide (0.40 miles) This plume is now beneath the town and and will eventually reach the Jacques-Cartier River [36, 37] at a migration velocity ranging between 13m to 68m per year (43 ft to 223 ft) [38]. The Sterling plume is smaller, measuring a mile long (1.6 km) and half a mile (804 m) wide. In 2007, geological reports indicated that the plume was moving toward the Potomac River [39].
How TCE behaves inside the body
Both the ATSDR and the International Agency for Research on Cancer (IARC) have labeled TCE as a probable human carcinogen based on epidemiological studies done on mice and rats. Under the International Union of Pure and Applied Chemistry (IUPAC), TCE is classified as a Group B agent because of proven evidence of carcinogenicity in experimental animals [40]. In Europe, the European Union Commission Expert Groups classified TCE as a human carcinogen in 2001 [41].
When inhaled, between one-third and two-thirds of TCE is rapidly absorbed into the lungs. The rest is exhaled. In the case of dermal contact, TCE removes fat from the skin thus increasing its own absorption. Once in the blood, TCE will be distributed to most tissues, but it metabolizes in the liver where it is broken down further and will eventually be excreted in the urine within a day [42]. Small quantities may be stored in body fat for a brief period. Chronic exposure allows TCE to build up in the body. Two medical tests can detect the presence of TCE in humans: a breath sample taken soon after exposure, and a blood or a urine sample taken after larger exposure. A study done by toxicologist Dr. Forkert indicated that in mice and in humans, TCE and its by products are metabolized in the human reproductive tract, and can adversely affect the normal development of sperm [43]. This could mean that a sperm test could also be used as another option in detecting TCE in the body.
In 2001, the EPA produced a draft risk assessment based on the most up-to-date informations, which explains that TCE may induce neurotoxicity, immunotoxicity and developmental toxicity (TCE crosses the placenta in animals and humans and can accumulate in the fetus) [44]. The Agency for Toxic Substances and Disease Registry (ATSDR) agrees with EPA and states that long term exposure to small amounts of TCE in water may “cause liver and kidney damage, impaired immune system function, and impaired fetal development in pregnant women” [45]. The EPA concluded that TCE “posed a more significant human health risk than previous studies had indicated”[46]. The EPA has also “considered the potential for cumulative exposure to not only TCE, but also to its metabolites DCA and/or TCA, and VC regardless of their source” [47].
Chronic (long-term) exposure to TCE induces: nausea, intolerance to fatty foods, respiratory irritation, renal (kidney) toxicity, and immune system depression. If alcohol is consumed, TCE’s toxic effects in the body will increase [48]. Cases of ‘degreaser’s flush’ (transient redness and itching of the back, neck, and face) have been reported after the ingestion of alcohol [49].
Dr. Claude Juneau stated that there are at the moment, 240 cases of various cancers in Shannon, 12 of which are brain cancers [50]. This is important because brain cancer is not on the list of the usual cancers related to TCE exposure. Brain cancers, however, are known to occur when people are exposed to vinyl chloride which, according to the EPA (2000), is a known human carcinigen [51, 52]; VC is one of the sub-products of TCE. Most of these cancer cases are within an area called the “Red Triangle” which was mentioned earlier [53]. The number of cancers within the population may increase as more past and present residents from Shannon and from the Base are diagnosed with cancer.
What epidemiological studies say about TCE
Numerous occupational and non-occupational studies have been done on TCE and its effect on humans; the results are not definitive.
One study carried out by the Agency for Toxic Substances and Disease Registry (ATSDR) compiled data on 4,280 residents from Michigan, Illinois and Indiana. Here the results found no evidence to link increased cancer rates to TCE exposure [54].
Another ATSDR study looked at participants who had been exposed to TCE concentration in drinking water between 2ppm to 19.380 ppm for18 years (the WHO recommends no more than 5 ppb). The results here indicated an increase in health complaints in people who were exposed to higher TCE concentrations with an increase in the rate of strokes. Still, no clear cause and effect could be established between the TCE and health issues [55].
Other studies carried out by the National Toxicology Program on animals noted that tumors in the lungs, liver and testes were present in rats and mice exposed to massive doses of TCE. In the rodents, however, problems developed when they were exposed to much higher levels of TCE than encountered by human populations.
Epidemiological studies have looked at specific characteristics which define cancer clusters in different locations affected by TCE groundwater contamination. For a cancer cluster to be considered, it must show characteristics which take in consideration the occurrence of a greater than expected number of cases of a particular disease within a group of people, the geographic area, or the period of time. There are four characteristics inherent to cancer cluster that we do not see in Shannon. They are: 1) a large number of cases of one type of cancer; in Shannon there are numerous types of cancer, 2) a rare type of cancer rather than common types, 3) an increased number of cases of a certain type of cancer in an age group that is not usually affected by that type of cancer, e.g. in children and 4) unmetastatized primary cancer cases [56]. According to these defining characteristics, the residents of Shannon do not have a cancer cluster within their population.
As for the residents of Sterling, no information on cancer rates are available at this time. ATSDR has opted not to perform a review of health outcome, because of the relatively short period of time from the discovery of the contamination and the installation of carbon filters. Other reasons, which are similar to Shannon’s are the small number of people being exposed makes it impossible to detect statistical differences in cancer rates [57].
Establishing cause and effect between TCE and cancers
Researchers are aware that, when looking at TCE , people are exposed to a complex mixture of metabolites. This, coupled with other environmental pollutants, may enhance carcinogenicity by creating a synergistic effect. Now, where do we turn to prove that people from Shannon and Sterling as well as others in the world, who are in the same situation, suffer from TCE induced cancers?
Well we could use the ATSDR highest cancer slope factor of 0.02 to 0.4 mg/kg/day, which is the risk associated with a unit dose of a carcinogen. In the Public Health Assessment for Hidden Lane Landfill, ATSDR is quite specific. They state that “Lifetime excess cancer risk is estimated by assuming the maximum daily adult dose (a person weighing 70 kilograms drinking 2 liters of water containing TCE at the maximum concentration) continues for a 70-year lifetime. (The potential exposure is also doubled to account for inhalation and dermal exposures associated with use of the well water.) Using an oral cancer slope factor of 0.4 (mg/kg/day)-1, the predicted increased risk of cancer would be moderate to high” [58]. This cancer slope factor would require public health departments to follow exposed people for a long period of time, so do we have any other more precise means to prove that TCE induces cancer in chronic exposure? Well we might…..
A coalition of Shannon residents have decided they can prove, via a new approach, that TCE is responsible for the different cancers found in their population. They will present this evidence in an upcoming lawsuit scheduled for this fall. According to Dr. Sidney Finkelstein who works for RedPath Integrated Pathology in Pittsburgh, the results of molecular toxicology done on cancerous tissue samples from victims is showing promising results. TCE has a specific signature in the form of an identical genetic mutation on chromosome 3.
People who have been exposed to TCE for an unknown period of time may show characteristic changes on this chromosome. This causes mutations which are forerunners to tumor formation and eventually to cancer [59]. It must, however, first be proven that TCE induces DNA or chromosomal damage to cells and their daughters before this specific signature can be accepted. If this new technique is shown to prove the mutagenic mode of action of TCE, and that human tumors are a result of exposure, this will be very exciting to the research community. I sincerely hope that this “new approach” will work and will pave the way for new brands of studies.
Is it possible to decontaminate groundwater affected by TCE?
Yes. In the past, contaminated soils were incinerated and groundwater was pumped through carbon adsorption/absorption filters. Decontamination processes have evolved into Bioremediation, where microbes such as methanotropic bacteria are used to break down TCE within groundwater [60] and Phytoremediation which uses plants.These two have gained attention as relatively inexpensive methods of TCE break down or removal. Trees such as hybrid poplars (Populus trichocarpa x Populus) and Eastern cottonwoods (Populus deltoides) planted over contaminated soils and groundwaters, are showing signs of being very effective. They are both fast growing and can uptake TCE in their roots. These trees are also aethetically pleasing giving a contaminated site, especially in an urban area, a park-like look. Trees root systems, however, cannot grow deeper than 10m and thus are only suitable for shallow aquifers [61].
Other decontamination methods include using products such as molasses, whey, vegetable oil, fertilizer and calcium peroxide. Molasses or whey can be applied directly to the soil or molasses and vegetable oil can be injected into the aquefer. The electron exchange between donors and receptors encourages bacteria to feed on contaminated soils and groundwater [62]. This ‘feeding frenzy’ is said to render TCE less toxic and potentiolly harmless.
Conclusion
TCE is a world-wide contaminant. TCE, being tasteless, cannot be detected by physically drinking water. The only way to detect TCE is through well water analysis. TCE also degrades over time producing by-products, such as vinyl chloride, that may have more cancer causing potential than just TCE. TCE can be detected in the blood and urine soon after exposure, but when people are exposed to TCE repeatedly, it will accumulate in body fat. We also learned, however, that numerous epidemiological studies have been carried out on the potential effects of TCE, but they estabalished no specific link between cause and effects. Rats and mice show adverse health effects when exposed to TCE, but only when they are subjected to greatly higher dosages than human populations ever find.
In the United States and in Canada, people have been exposed by ingestion, inhalation and or dermal contact. The residents of Shannon and Sterling were exposed specifically via ingestion and inhalation. Although we do not know exactly how long residents of Shannon have been drinking contaminated water, we know that in Sterling, residents were exposed from 1971 until three years ago when carbon filtration systems were installed. We now know that in Shannon at least 240 residents were diagnosed with cancer and the residents blame TCE. Here, however, the cancers do not meet the characteristics of cancer clusters. In Sterling, because carbon filtration was installed on affected wells, no health follow-ups were deemed necessary.
There is a possibility that, thanks to molecular toxicology, specific chromosome signatures in cancerous tissues may identify the culprit agent, similar to TCE’s specific signature on chromosome 3. If chromosomal signatures can be identified, conclusions as to cause and effect could potentially be reached more quickly.
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Rosemary Stephen (2009). Trichloroethylene (TCE) Water Contamination Elements: Environmental Health Intelligence; http://elements.healthspace.com/
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