- Ethylene oxide is classified as a carcinogen, mutagen, and teratogen for humans and has no safe exposure levels.
- The gas also causes other health problems and is an explosion and fire risk.
- To avoid exposure, problems specific to the process must be addressed to prevent leaks, spills, and overfeeding.
- Reliable sensors that are accurate and fast can be crucial in the detection and prevention of gas buildup and exposure.
The International Agency for Research on Cancer has classified ethylene oxide as a category one carcinogen, so human exposure should be maintained at zero if possible or below the prescribed limit. The gas has been receiving attention due to recalls due to detection in spices. Workers are in greater danger as they could be subject to chronic exposure at higher than permissible levels. Safety managers at fumigation centers can use this article to determine how to control the gas.
Ethylene Oxide as Fumigant
Ethylene oxide (EtO) is a colorless gas with a fruity odor at ambient temperatures, which dissolves in water, organic solvents, and alcohol. The gas has a half-life of 69-149 days in air and 12-14 days in water.
EtO is mainly used to produce other chemicals. Ethylene oxide is used as a pesticide and disinfectant for the fumigation of food and cosmetics and for sterilizing heat and moisture-sensitive medical devices that account for 50% of all medical tools. Around 95% of the gas is used as a pesticide and disinfectant to sterilize medical devices. In the US, less than 1% of EtO is used as a fumigant.
As a fumigant, EtO is used for the following purposes:
- Pesticide: The gas controls pests in bulk grains and tobacco in storage and transit.
- Disinfectant: EtO prevents microbial spoilage and contamination by microbes, particularly coli and Salmonella, in packaged food, spices, and contact surfaces.
EtO gas use as a food fumigant is prohibited in some regions like the European Union because it is carcinogenic and mutagenic, leading to several recalls of spices from India between 2020-2021.
Exposure Points
People can be exposed to ethylene oxide if they work with the gas, live near fumigation centers, through tobacco smoke, and lastly, by consuming products fumigated by the gas.
Figure 1.: A map showing the affected neighborhood of EtO fumigation centers for spice and nuts in New Jersey, US. Blue circles indicate centers that are a cancer risk for surrounding populations. The different colors, red, orange, and yellow, indicate areas in a 1, 3, and 5-mile radius of the fumigation centers, Minovi, 2023. (Image credits: Union of Concerned Scientists)
Occupational exposure
Workers at places producing or using EtO can be exposed to higher doses of the gas than the public. Workers at fumigation centers are exposed to EtO through inhalation or skin contact. Acute exposure to high levels can occur due to accidental spillage, and personnel may be exposed to low concentrations over more extended periods. Manual handling of packaged items from shipping containers exposes workers to higher than permitted levels of gas since the storage units have no ventilation. Ethylene oxide at 1.7 ppm was recorded in some containers, where the occupational allowed levels are only 1 ppm.
Neighborhoods
People living, working, or attending schools in neighborhoods within a five-mile radius of EtO fumigation centers are also considered at risk of getting cancers by the US, see Figure 1. Of nearly 100 EtO fumigation and sterilization centers in the USA, 23 emit levels that can be a cancer risk for surrounding neighborhoods, according to the US Environmental Protection Agency (EPA). Children are at greater risk as they play outdoors; moreover, they have higher respiration rates and have not yet developed sufficient capacity for detoxification.
EtO Hazards
Ethylene oxide is a health and explosion risk for workers and the neighborhood, and its properties leading to specific effects are discussed below; see Table 1.
Table 1: Hazard summary of ethylene oxide. (Credits: NJ Health Hazardous Substance Fact Sheet)
Health impact
The health impact of EtO depends on the type of exposure, which can be through inhalation or contact, and the duration of exposure.
Acute Health Effects
Effects of short-term exposure to ethylene oxide occur immediately or after some time and are as follows:
Skin contact: EtO gas can irritate and burn on contact with skin and eyes, with the possibility of eye damage. Contact with undiluted liquid EtO due to spillage can cause frostbite.
Inhalation: Breathing the EtO gas affects the respiratory system. Lower levels irritate the nose and throat, causing shortness of breath and coughing. Exposure to high doses can cause pulmonary edema. The gas also leads to headaches, dizziness, nausea, vomiting, and seizures.
Chronic Health Effects
Health effects due to chronic exposure take time to manifest symptoms but can last for months and years.
Cancer hazard: Ethylene is carcinogenic and causes leukemia in humans. In animals, it also causes blood, lung, and stomach cancers.
Teratogen hazard: Ethylene oxide may be a teratogen in humans and could cause abortions and damage the developing fetus.
Reproductive Hazard: EtO could damage male reproductive glands.
Other effects: Repeated exposure to EtO can cause bronchitis and damage to the liver and kidneys. High or repeated exposure damages nerves, causing weakness in limbs and “pins and needles.” It could also lead to skin allergy.
Health authorities recommend eliminating improper and unnecessary to minimize ETO exposures.
Explosion risk
Ethylene oxide is highly flammable and is a dangerous explosion and fire risk. The flammability limit is 3% in air. Pure EtO, or 100% of the gas, is flammable even in the absence of air. It is more of a fire risk than hydrogen. After ignition, the fire races back to the source at a speed of 1,800 to 2,400 m/sec!
The gas in closed containers can mix with air and vapor to become ignitable.
Workplace Exposure Limits
Due to the ethylene oxide health and fire risks, various agencies in the US have strict recommendations for monitoring the gas levels at all times.
Occupational Safety and Health Administration (OSHA): The permissible exposure limit (PEL) set by OSHA is legally implementable for industries.
- For an 8-hour work shift, the limit is 1 ppm, and averaged over any 15 minutes, it is 5 ppm.
National Institute for Occupational Safety and Health (NIOSH): The recommended exposure limit (REL) levels are >0.1 ppm. EtO levels averaged over any 10 minutes should not exceed 5 ppm.
ACGIH: The recommended threshold limit value (TLV) averaged for an 8-hour work shift is 1 ppm.
US Environmental Protection Agency (EPA): The EPA sets limits for toxic chemicals to protect the general public. EPA wants EtO levels in the air to remain below 110 ppm for any 1 hr period.
The levels mentioned are for air. Skin contact with EtO is dangerous at lower concentrations. Since it is carcinogenic, any levels of the gas are a risk.
Preventing EtO Hazards
Some common causes have been identified as occupational risks, which can be addressed to control EtO risks for workers and beyond.
Overfeeding: Overfeeding is the leading cause of EtO accidents. EtO is fed into a container with items to be fumigated. Extra gas is burned off or converted to water and carbon dioxide through catalytic conversion to keep levels within permissible levels. The following measures can prevent overfeeding:
- Use the correct cycle for the product.
- Ensure interlocks and safeguards like back vents are working.
- Prevent EtO build by washing or aerating fumigated products.
- Monitor EtO lower flammable levels with sensors that give results in real-time and are not slow.
- Regularly maintain the whole system, including the computer system, controller, etc.
Storing and handling ETO: Store in tightly closed containers in cool, shaded, and well-ventilated spaces. Do not smoke where EtO is stored or used. Also, avoid any other generation of sparks.
Leaks and spill management: Leave a space with a tiny leak or spill. Evacuate the building in significant spillage and call the fire department.
Rescue preparedness: Only properly trained people should attempt rescue. Use full protective gear to rescue people from areas of spills or leaks.
Avoid contact: Prevent skin and eye contact. Immediately wash in case of contact with liquid EtO.
More detailed instructions for workers and employers are available in this resource, prepared by NIOSH, EPA, and the Ethylene Oxide Sterilization Association (EOSA).
Monitoring EtO Levels
One of the vital measures to prevent ethylene oxide hazards is to monitor its levels accurately and provide timely alerts around the clock. One of the causes of explosions is overfeeding, which can occur due to slow sensors. Interscan produces five sensors for EtO for real-time estimations with varying resolutions, some of which can measure small concentrations even in parts per billion. These can be used in fixed instruments to provide permanent monitoring. Portable versions can be used in areas with spills or leaks or to monitor the neighborhood. Such instruments can help fumigation centers make workspaces safer and address general public health concerns.
Contact us at Interscan to find the correct sensor for your fumigation needs.
Sources
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Darya Minovi. 2023. Invisible Threat, Inequitable Impact: Communities Impacted by Cancer-Causing Ethylene Oxide Pollution. Cambridge, MA: Union of Concerned Scientists. https://www.ucsusa.org/resources/invisible-threat-inequitable-impact/
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