Since first hitting the market around 30 years ago lithium-ion batteries are now present in a wide range of every-day consumer products, such as mobile phones, laptops, tablets, digital cameras, power tools and electric and hybrid automotive vehicles.
In 2016, consumer products accounted for the production of batteries with a total storage capacity of about 45 gigawatt-hours (GWh), which represents the output of approximately 200 million photovoltaic panels, or 22,000 utility-size wind turbines. The US Department of Energy predicts that production of these batteries will more than triple to around 164 GWh by 2020.
The storage of lithium batteries is becoming more frequent in the workplace as usage is increasing due to their high energy and power densities. Exceeding the thermal stability limits of a lithium-ion cell can result in thermal runaway. Such failures can generate intense heat, smoke and toxic substances, including hydrogen fluoride (HF). This poses a potential health and safety risk to employees and has prompted a need for risk management plans.
Golder’s risk assessment and toxicology team was called upon by a client to conduct a human health and toxicological risk assessment of a lithium-ion battery testing and storage facility in Australia to assess potential HF exposures to staff in the event of thermal runaway occurring.
While thermal runaway was expected to be a rare occurrence for the battery testing facility, assessment of the risk to worker health was nonetheless prudent. The project required consideration of the duration of acute exposure under a defined workplace scenario. The key exposure pathway assessed was inhalation as HF is readily absorbed in the upper respiratory tract and lungs, which is the most sensitive target of acute HF toxicity.
An estimation of emission rates for HF and subsequent conversion to HF indoor air concentrations was included in the assessment. Emission rates of HF depended on the degree of charge of the batteries, which was incorporated into scenario models, adding to the complexity and range of results. A toxicological assessment of the concentration-time response was undertaken to characterise potential risks to workers.
The results showed that the modelled indoor air concentrations exceeded the selected guideline and the potential health consequences required further analysis. Combining risk assessment principles with toxicological understanding of HF behaviour allowed a more detailed assessment of the actual (likely) risks. The project aided the client by recommending mitigation measures to reduce the risks inferred by the study.
This project also illustrated the challenges and complexities in assessing rare emergency exposure scenarios that may not fall within the routine guidance and methodologies commonly employed in an environmental contaminants risk assessment. This methodology could be applied to inform risks for other lithium-ion storage and handling situations, factoring in specific exposures and occupational settings for each risk assessment.
More information about this project can be viewed here.