You are standing before the shipping department of a machine shop, ready to present a safety briefing on a new process and a new chemical hazard never before managed by this company. “The expandible foam required by our new client contains methylene bisphenyl isocyanate,” you say, “better known as MDI. That’s why we’re going to mandate respirators, at least at first.” The workers begin speaking quietly to each other. You can’t help but notice. “Is something wrong?” you ask. “We know about MDI,” says the shop steward, surprising you. “Most of us worked at the chemical plant that shut down a few years ago. It gave a bunch of us asthma.” FRAMING WORKER SUSCEPTIBILITY In August 2020, AIHA’s Content Portfolio Advisory Group (CPAG) approved the work that would eventually be titled the Susceptible Worker Protection Technical Framework (SWPTF). As defined by AIHA, technical frameworks are documents that identify the core knowledge and skills needed for effective performance in a specific practice or expertise. I was one of nine authors of the SWPTF, which was published in May 2023. There are currently 16 frameworks available from AIHA. The purpose of the framework was to provide a useful resource for both new OEHS professionals and those with extensive experience who are seeking to benchmark their practice in this specific domain. The authors hope that this document will be a functional introduction to the topic, emulating the experience of sitting down with a tenured professional. However, the authors also recognized a need to define key principles and terminology to ensure that the theories behind the practice were properly established. The terms susceptible and vulnerable are not used consistently in published literature on either topic. The framework defines worker susceptibility as “the combination of genetic factors or exposome that impact the severity of exposure to a given agent.” Contrast this with discussions of vulnerability, which are more strongly associated with social or economic circumstances related to precarious employment or ethical treatment. Extensive work has been done to define the exposome, which is the sum of internal and external exposures from the environment (including those away from work). The NIOSH Total Worker Health initiative and AIHA’s Total Exposure Health Advisory Group provide extensive resources to better understand how the exposome impacts worker susceptibilities. The framework was written to help OEHS professionals consider issues to think about when protecting workers, not as a conformance standard or proscriptive guide. The right steps to protect against health effects from worker susceptibility will vary by organization, but the principles on which these considerations are established apply to all cases. ALIGNING ON KEY PRINCIPLES Protecting workers with susceptibilities also requires our community of practice to discuss and accept positions on a few key principles. First and perhaps most importantly, worker susceptibility is a dynamic of risk, not of the worker. When an organization consciously accepts the risk of working with an agent, it is also accepting the need to manage exposures with the additional parameter of potential worker susceptibilities. Susceptibility results from the interaction of the agent, exposure dynamics, and individual. Susceptibility is not a shortcoming or drawback of a specific worker. This principle is consistent with the inverse case: we do not allow hearing-impaired workers to be exposed to excessive noise without protection, or particularly resilient workers to be exposed to heat above exposure limits, simply because we believe the risk of health effects is lower for them. Ethical protection of workers is predicated on not discriminating against workers based on genetic factors or exposome. Many susceptibilities are unknown either to the worker or to the organization that employs their labor.

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