Ethylene Oxide - the chemical industry's defense of cancer risk

The chemical industry is mounting a defense of its toxic product

The EPA Integrated Risk Information System (IRIS) program released its Draft hazard assessment of ethylene oxide last summer, with its updated evaluation of the cancer risks from inhaling ethylene oxide (IRIS, July 2013).  Ethylene oxide is already known to be a very toxic chemical. It is one of the 33 most hazardous air pollutants identified by EPA as posing the greatest human health risk in the largest number of urban areas.(IARC Vol 97, 2008) At room temperature, ethylene oxide is a gas. It is toxic, flammable, explosive and causes cancer.

Overall, the EPA IRIS program's draft chemical assessment is pretty good. If it is finalized without being weakened by industry interference, it would provide the scientific underpinning for stronger pollution restrictions, thereby reducing cancer risks.

So it is not surprising that the chemical industry is in full chemical-defense mode.

Over the last few years, as EPA was conducting its review of ethylene oxide, the chemical industry was funding research arguing that ethylene oxide isn’t harmful at the levels that people are exposed, or isn’t as harmful as EPA has calculated, or some such version of the Four Dog Defense strategy that Big Tobacco developed to defend cigarettes (see recent comments on ethylene oxide by the American Chemistry Chemical industry and others at Docket ID No. EPA-HQ-ORD-2006-0756).

Now that the EPA is preparing to convene a scientific peer review committee to review its ethylene oxide assessment, it is seeking independent experts to serve on the committee. About a half-dozen scientists with research funding or collaborations with Dow Chemical or the chemical industry trade association are short-listed to serve on the “independent”peer review committee. None of their financial and collaborative relationships with the chemical industry are identified in public biosketches see the List and Biosketches of Candidates here).

If any of these industry-collaborating individuals are selected for the committee, it seems to me that it would violate EPA’s own guidance that says these committees are supposed to be comprised of scientists without financial conflicts or the appearance of a lack of impartiality. And, it would violate the recommendations of the 2014 National Academies report on the IRIS program, that advises against having financially-conflicted experts serve on scientific panels.

So what is it that the chemical industry doesn’t want us to know about ethylene oxide?

The EPA IRIS draft assessment concludes that ethylene oxide causes cancer in people.  Ethylene oxide exposed workers have an elevated risk of breast cancer, leukemia and non-Hodgkin lymphoma (Steenland et al 2003, 2004). Ethylene oxide exposed lab rodents had similar cancers, and cellular studies confirm that ethylene oxide causes genetic (DNA) mutations and chromosomal damage that can lead to cancer (see summary of relevant cancer data here).

It is most concerning that the IRIS draft finds a strikingly high cancer risk from exposure to high but realistic levels of ethylene oxide; an excess of 1,800 cancer cases per 1 million people that breath air contaminated with 1 µg/m3 ethylene oxide (Table 1-1, page 1-6).  This is 1,800 times higher than what EPA deems an acceptable risk level for the general population. (Maximum ambient air exposure models have been measured as high as 1 µg/m3 [IARC Vol 97, 2008]). 

How are people be exposed to ethylene oxide?

People can be exposed to ethylene oxide at work, such as when sterilizing or fumigating medical and dental equipment, when manufacturing chemical products such as polyester that are made with ethylene oxide, when sterilizing food spices, when making plastic products, and when fumigating agriculture crops (See IARC Monograph here).

People can also be exposed to ethylene oxide if they are working or living near sterilizer facilities, fumigation operations, or other places where ethylene oxide is used or manufactured in large volumes. According to the EPA Toxic Release Inventory, industry reported releasing 324,000 pounds of ethylene oxide waste, mostly into the air as either fugitive (110,800 pounds) or point source (197,400 pounds) air emissions (EPA TRI, 2012).

What is ethylene oxide used for?

Ethylene oxide is a human-made industrial chemical that is a key raw ingredient in the production of many industrial chemicals including ethylene glycol, which is used to make antifreeze and polyester. Polyesters are used in many household and industrial products including fabrics for home furnishings, upholsteries, factory conveyor belts, car safety belts, plastic bottles (PET, or polyethylene terephthalate plastic), tarps, canoes, insulation for wires, wood finishes such as on guitars and pianos, and liquid crystal displays (LCDs). Ethylene oxide is also used to make polyethylene glycols, in perfumes, cosmetics, paint thinners, and plasticizers. (See report on world uses of EO here)

A much smaller amount of produced ethylene oxide –  less than 0.1% - is used as a pesticide, or for sterilizing equipment that cannot be heat-sterilized such as drugs, some medical equipment, packaging, foods, museum artifacts, furs, railcars and aircraft, and beehives.

The US produces about 4 million metric tonnes of ethylene oxide annually (about 9 billion pounds), making it the largest producer in the world. Total global production is about 19 million metric tonnes annually, and rising.