Human Health Effects of Trichloroethylene: Key Findings and Scientific Issues

Abstract

Background

Background: In support of the Integrated Risk Information System (IRIS), the U.S. Environmental Protection Agency (EPA) completed a toxicological review of trichloroethylene (TCE) in September 2011, which was the result of an effort spanning > 20 years.

Objective

We summarized the key findings and scientific issues regarding the human health effects of TCE in the U.S. EPA’s toxicological review.

Methods

In this assessment we synthesized and characterized thousands of epidemiologic, experimental animal, and mechanistic studies, and addressed several key scientific issues through modelling of TCE toxicokinetics, meta-analyses of epidemiologic studies, and analyses of mechanistic data.

Discussion

Toxicokinetic modelling aided in characterizing the toxicological role of the complex metabolism and multiple metabolites of TCE. Meta-analyses of the epidemiologic data strongly supported the conclusions that TCE causes kidney cancer in humans and that TCE may also cause liver cancer and non-Hodgkin lymphoma. Mechanistic analyses support a key role for mutagenicity in TCE-induced kidney carcinogenicity.

Recent evidence from studies in both humans and experimental animals point to the involvement of TCE exposure in autoimmune disease and hypersensitivity.

Recent avian and in vitro mechanistic studies provided biological plausibility that TCE plays a role in developmental cardiac toxicity, the subject of substantial debate due to mixed results from epidemiologic and rodent studies.

Conclusion

TCE is carcinogenic to humans by all routes of exposure and poses a potential human health hazard for noncancer toxicity to the central nervous system, kidney, liver, immune system, male reproductive system, and the developing embryo/fetus.

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Persons working with or working in areas using trichloroethylene in Baldonnel have suffered the following illnesses. 

Untimely deaths are marked thus *

      • Brain Tumour*
      • Colorectal Cancer*
      • Crohn’s Disease*
      • Lung Cancer*
      • Multiple Sclerosis
      • Non-Hodgkin’s Lymphoma*
      • Oesophageal Cancer*
      • Pancreatic Cancer*
      • Parkinson’s Disease
      • Renal Cancer*

Organic solvents and Multiple Sclerosis susceptibility

Abstract

Photo of dichloromethane (DCM) as stored by Irish Air Corps in 2015. DCM was banned in the EU in 2012.
Objective

We hypothesize that different sources of lung irritation may contribute to elicit an immune reaction in the lungs and subsequently lead to multiple sclerosis (MS) in people with a genetic susceptibility to the disease. We aimed to investigate the influence of exposure to organic solvents on MS risk, and a potential interaction between organic solvents and MS risk human leukocyte antigen (HLA) genes.

Methods

Using a Swedish population-based case-control study (2,042 incident cases of MS and 2,947 controls), participants with different genotypes, smoking habits, and exposures to organic solvents were compared regarding occurrence of MS, by calculating odds ratios with 95% confidence intervals using logistic regression. A potential interaction between exposure to organic solvents and MS risk HLA genes was evaluated by calculating the attributable proportion due to interaction.

Results

Overall, exposure to organic solvents increased the risk of MS (odds ratio 1.5, 95% confidence interval 1.2–1.8, p = 0.0004). Among both ever and never smokers, an interaction between organic solvents, carriage of HLA-DRB1*15, and absence of HLA-A*02 was observed with regard to MS risk, similar to the previously reported gene-environment interaction involving the same MS risk HLA genes and smoke exposure.

Conclusion

The mechanism linking both smoking and exposure to organic solvents to MS risk may involve lung inflammation with a proinflammatory profile. Their interaction with MS risk HLA genes argues for an action of these environmental factors on adaptive immunity, perhaps through activation of autoaggressive cells resident in the lungs subsequently attacking the CNS.

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Anecdotal evidence has been emerging for some time of potential illness clusters at Casement Aerodrome to which Multiple Sclerosis has now been added. We are calling for these potential clusters to be investigated by competent authorities.

Suspected illness clusters currently include.

Blind Date – Another human cost of the Irish Air Corps Toxic Chemical Health & Safety scandal

For a very long time now both my mother and my sister have been encouraging me to start writing a blog. ‘Tell people your story,’ they said. I never felt I’d anything interesting to write. Well my mother pointed out something interesting today. She said ‘it’s been twenty years since the date your eyesight went’. I never really thought of myself as getting old, but twenty years is a long time. How much has changed.

Back in 1996, I was 18 and in my second year as an apprentice with the Irish Air Corps. I had joined up when I was 16 and with typical teenage brashness I thought I was the shit. And sure why not. All I’d ever wanted to do was serve. After a youth watching Rambo, Top Gun and Hot Shots on an endless loop, I had my whole career planned out. Alas it was not to be. Over a period of a few weeks around March/April 1996 I started messing up a lot; maps upside down, knocking over pints, not being able to read my writing, not saluting officers, that sort of thing. I was also extremely fatigued.

I still remember the first trip to the medical aid post. ‘Put your hand over your right eye and read the chart,’ said Commandant Collins. Not a problem: Z W T 1 3 7 q e y. Easy. ‘Now cover up your left eye and read the chart’. ‘OK’, I said, ‘Can you put the chart back up please’. After that the fun and games started. After several trips to the medical aid post I found myself on rotation in and out of the Eye and Ear. I had every type of blood and eye test done. Along with an MRI I was being tested initially for a brain tumor and diabetes and then a whole rake of other conditions I’d never heard of at the time. They hadn’t a clue what was wrong. All this time the sight in my right eye was getting worse and the sight in my left eye decided to start packing it in. It’s hard to describe. Blurry cloudy vision. Loss of sharpness with your central vision effected the most. If you look at someone straight on from about a meter away, you can make out their hands and legs but they’ve no head.  Beyond a meter people become more like blurry colours moving around.

Although a total pain in the ass and not exactly what I wanted to be doing with my life, these trips to the Eye and Ear were entertaining nonetheless. As nobody knew what was wrong every doctor and med student wanted to poke around my eyeballs. My friends from the Air Corps who would accompany me on these trips would get rather jealous as a young pretty female med student would bend over and look into my eyes with some strange instrument. Then again they had a different view.

On another occasion though I was on my own. So what happens is you’re put in a big waiting room and given a raffle ticket. ‘Take a seat your number will be called’. From what I remember I was the youngest person there. Everyone else seemed to me at that time to be ancient. You have to really picture this scenario. It’s a room full of people with bad sight or bad hearing or because of their age, both.  A voice bellows from the top of the room ‘No. 17’ (it could have been any number I can’t remember). ‘Hmm’ I think to myself, ‘it might have been handy if I’d asked what number my ticket was’. There’s a pause, a bit of shuffling and mumbling. Half the people can’t see their tickets and the other half are asking ‘did someone say something’. ‘No. 17’ the voice from the top of the room bellows again. I get a nudge on the arm from an old lady beside me: ‘Excuse me son what number ticket do I have’. Absolutely comical.

On one of these trips to the Eye and Ear to get poked at again by so called experts who’d no idea what was wrong I was sitting in the waiting room when I heard a nurse talking to an older man. I was positive I recognised his voice. Getting up I went to the other end of the corridor. ‘Uncle Danny,’ I said, ‘Is that you’. (Uncle Danny was my mam’s uncle). ‘It is’, he said, ‘who’s that’. ‘It’s Wes,’ I said, ‘there’s something wrong with my sight. What are you here for?’ ‘My sights going too’, he said with a worried sigh. Not being able to see each other clearly we both could tell we were looking at each other and thinking ‘what the …’ The nurse was thinking the same. She went off to get the doctor.

With the extended family brought in we discover we have a condition called Leber’s hereditary optic neuropathy (LHON). At the time there was no test in Ireland because it is a genetic condition. A cousin of my grandmother had been clinically diagnosed with mutation 11778. After we told the doctor about LHON I still remember the doctor taking down a book and blowing off the dust. (Or at least that’s my version of the account). ‘Yes that’s what you have. Some of the cells in the optic nerve are dead and the signal isn’t going to the brain. It’s a very rare condition’. Personally I’d have preferred to have won the lotto.

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As mentioned in the above story Leber’s Hereditary Optic Neuropathy involves genetic mutations that can lead to blindness through optical nerve mitochondrial depowering. One very interesting aspect to this disease is that only a minority of persons with the mutation actually suffer blindness. The breakdown by sex is that only 10% of females and only 40% of males with the mutation go blind.

For years the “trigger” for the blindness was unknown but in the past 20 years a number of trigger chemicals have been identified. One of these chemicals is an Alkane known as nHexane and it is important to note that this chemicals was involved in the intoxication & injury of 2 Air Corps technical personnel in 2015 that lead to the eventual Health & Safety Authority investigation.

Furthermore the neurotoxicity of nHexane is enhanced significantly in the presence of Methyl Ethyl Ketone (MEK). This is another chemical that was also used without any precaution for decades in the Irish Army Air Corps.

It is important to also note that the person in the story above went blind within two weeks of starting work in Engine Repair Flight (ERF). As an Air Corps Apprentice he only had to spend 10 weeks work experience in this location which were, unfortunately for him and others, life changing and career ending. ERF and its associated Non Destructive Testing (NDT) workshop (photographed below in 2007), were possibly one of the most chemically toxic workplaces anywhere in Ireland.

This workshop was found to be 3½ times over allowable limits for Dichloromethane (DCM) in 1995 but personnel were not warned and it was left operational for a further 12 years. During that time there were at least 5 adult deaths, at least 1 child deaths and and at least 2 children born with severe genetic mutations that we believe were associated with chemical exposures in this workshop alone. Chemicals in use were carcinogenic, mutagenic & teratogenic.

The engineering officer who commissioned these air quality tests is still serving in the Irish Army Air Corps in a senior role as is the engineering officer who ordered the test results destroyed in later years.