Ammonia Risk Evaluation Good News—Or Not

Babies born in the year the United States Environmental Protection Agency (EPA) last set a human health assessment for ammonia are adults now, and it looks like it’s not as risky now than it was back then. What does EPA’s new assessment portend for facilities that use ammonia and the standard set by the Occupational Safety and Health Administration (OSHA) for workers who handle the chemical? Will You Be Affected? The new assessment may seem like good news for facilities that use ammonia. Fertiliser manufacturers, albeit the largest users of commercially produced ammonia, are not the only ones affected by EPA’s new risk assessment. Other industries that should take note of the updated human health assessment for ammonia include food producers; household product manufacturers; water purifiers; pharmaceutical and other chemical producers; any facility that uses an ammonia-based refrigeration system; combustion sources, such as some industrial boilers that use ammonia to reduce nitrogen oxide emissions; livestock operations; and wastewater companies, to name a few. However, the costs of using ammonia could rise if OSHA changes the worker health standard in response to EPA’s new risk assessment. The EPA risk value is much more stringent that limits set for workers by OSHA. The New Assessment Is Less Stringent EPA’s Integrated Risk Information System (IRIS) assessment is an evaluation of the non-cancer health effects of ammonia when it is inhaled. It includes an estimate of the amount of ammonia that one can breathe every day for a lifetime that is likely to be without harmful health effects. This is known as an inhalation reference concentration (RfC). The RfC for ammonia was developed from a 1989 occupational study that looked at the relationship between decreased lung function and long-term exposure to ammonia from workers at a soda ash plant. Ammonia was last evaluated by the IRIS program in 1991. The result of the re-evaluation recently posted by the EPA, the RfC is less stringent than what was previously on the IRIS database. The new RfC for ammonia is 0.5 milligrams per cubic metre (mg/m3). The previous RfC set in 1991 was 0.3 mg/m3. According to the EPA, respiratory effects have been identified as a human health hazard following inhalation of ammonia. This hazard determination is based on findings from multiple human studies in different settings (workers in industrial, cleaning, and agricultural settings; volunteers exposed for up to 6 hours under controlled conditions; and case reports) and animals. OSHA Limit Much Looser OSHA’s permissible exposure limit (PEL) for ammonia is 35 mg/m3, much less stringent than EPA’s new RfC and considerably less stringent than the National Institute for Occupational Safety and Health’s (NIOSH) recommended exposure limit of 18 mg/m3. A huge discrepancy between OSHA’s PEL and EPA’s RfC for ammonia has existed for years. EPA’s new assessment does not narrow that gap in any significant way. However, with renewed risk assessment focus on ammonia, OSHA will certainly be pressured to tighten its standard for ammonia in the workplace.

EHS Daily Advisor, 27 October 2016 ; ;