A New Domain
Advancing Protection for Susceptible Workers
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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.
Worker susceptibility is a dynamic of risk, not of the worker.
Managing worker susceptibilities must be a function of managing uncertainty in exposure dynamics, not managing the workers by excluding them from work. This is especially important in circumstances where workers may not be covered by regulations that protect them from such discrimination. This treatment comprises our second principle.
Third, we must acknowledge that the healthy worker paradigm has serious limits. Workers may be modeled as functionally equivalent receptors, but in reality, they are probability spaces of potential health effects given a population of doses. This is especially important when many occupational exposure limit derivations do not consider susceptible workers. The ACGIH TLVs do not consistently include or exclude susceptible workers, often because of limitations in peer-reviewed toxicology literature. This makes reading the documentation provided with the TLVs, and understanding how the exposure limits were derived, critically important. Complexity, especially in light of advances in precision medicine, the availability of consumer genetic testing, and the increase in medical device usage, is greater than ever before. Accepting and respecting scientific uncertainty as part of that complexity is our fourth principle.
Fifth, we must acknowledge that privacy is a complex topic. In combination with scientific uncertainty and unknowns related to worker susceptibility, privacy can become difficult to manage. OEHS professionals should expect to need support from allied professionals in crafting processes that respect and protect privacy.
With these key principles defined, the authors completed an extensive literature search to identify previously published information about susceptibility to specific agents. This resulted in the inclusion of a table of known risk modifiers. The authors believe it is the single most comprehensive resource for worker susceptibility sorted by agent. The table layout was chosen to reinforce the idea that managing susceptibilities is a responsibility that stems from conscious acceptance of the risk of exposure to a specific agent.
The table associates specific agents with genetic factors that may modify susceptibility. Published sources are identified for each agent with a known susceptibility. While descriptions of specific genetic factors are included, the table acknowledges specific agents even if the identified factors are not known on an individual worker basis.
OEHS professionals seeking to further understand the table may want to learn more about single nucleotide polymorphisms. As defined in the framework, SNPs are “the most common type of genetic variation among people, consisting of a variation in a nucleotide base in a specific DNA position in the genome.” The average person has millions of SNPs, and most are not associated with exposure risk modification. SNPs may be used as biomarkers for the risk of some conditions. One such SNP that may be known to the public is BRCA1/BRCA2, associated with the risk of breast cancer. More closely related to occupational health, SNPs are also suspected of increasing susceptibility to chronic beryllium disease. Workers who do not know they have a genetic predisposition to a disease are still just as likely to be at increased risk.
This concept functions the same for exposome exposures. The vignette at the beginning of this article discusses an experiential condition that would cause workers to be susceptible to MDI exposure. The workers in the shipping department may never be exposed to MDI over the OEL but may still experience health effects due to sensitization. The TLV documentation for MDI expressly states that it may not necessarily protect susceptible workers from possible sensitization or an allergic reaction in previously sensitized individuals. This nuance may go unnoticed until illness arises even though many OEHS professionals rely on TLVs and they may be referenced by allied professionals in medical, legal, or organizational functions. For this reason, it is paramount that OEHS professional leadership provide context to exposures.
One of the primary goals of producing the Known Risk Modifiers table was to provide OEHS professionals with an accessible way to prove to stakeholders that worker susceptibilities have been sufficiently identified to warrant consideration. By providing peer-reviewed references for each entry, the authors hope to confer the highest possible degree of legitimacy to OEHS professionals when they introduce difficult concepts to groups making exposure control decisions.
DEVELOPING COMPETENCIES The complexity of this information also highlights the need to define the knowledge, skills, and abilities (KSAs) necessary to appropriately practice in this domain. The framework identifies thirty-four KSAs, which are grouped into four competencies:
1. key principles of susceptible worker protection
2. exposure scenario assessments
3. scientific literacy
4. communication and strategy
KSAs within each competency are aligned with the AIHA Professional Pathway career levels. The early career level has 15 KSAs related to susceptible worker protection, the professional level has 14, and the senior professional level has 5. For each career level, the framework describes the capability associated with that level of competency. For example, the competency statement for the professional level is:
I know susceptibilities to agents I may encounter and can recognize agents with susceptibilities in other industries. I can read, understand, and implement publications and guidance on susceptible worker protection and help my organization implement exposure assessment and control strategies for susceptible workers. I am an important component of my organization’s risk control strategy.
While many seasoned OEHS professionals may not have developed the competencies needed to practice at a level that aligns with their general seniority due to the emerging nature of this domain, the framework authors hope that integration of this subject matter into education and practice will allow for the presented competencies to reflect practice in the foreseeable future.
As established in other frameworks, the degree of complexity dictating the progression of competencies is related to both the degree of novelty and the extent of trust invested in the individual by the organization. While early career professionals may be grounded in concepts for ongoing exposures, those at the professional level are expected to demonstrate understanding of uncertainty, the impact of the exposome, and the crafting of OELs. Senior professionals are relied upon to use derived guidance, adapt methodologies, and lead or develop organizational strategies.
Protecting susceptible workers is fundamentally a new domain of practice for OEHS. The framework authors hope that this foundational work will serve as a primer for those who need accessible information to manage existing exposures, as well as a guide to future education and professional development activities focused on specific practices or the dynamics of individual agents.
SCENARIOS MAKE IT REAL Included in the framework are ten practitioner scenarios written by the authors. Each scenario is intended to highlight an aspect or principle of susceptible worker protection and prompt organizations to discuss how they would handle the presented cases. These scenarios can be used as tabletop exercises for professional development, as part of a stress test of organizational processes, or to help inform risk tolerance decisions related to organizational management.
Presenting difficult ideas to organizations can lead to a form of psychological inoculation, whereby introducing the concept of susceptible worker protection in advance of a challenge of this nature can prepare an organization to address it. The process of psychological inoculation was first described in 1961 but has recently been applied to pressing topics such as limiting the impact of anti-science misinformation in social networks. The authors hope that discussion of these difficult topics in the context of a newly published framework can prepare stakeholders to better contextualize similar scenarios.
PREPARING FOR THE FUTURE In addition to the resources collected in the framework, the authors present a call to action that identifies three further works in this domain that need champions.
First, additional authoritative guidance is needed for agents that have the additional risk dimension of worker susceptibilities. Work done by ACGIH on TLV notations such as Skin, DSEN (dermal sensitization), and RSEN (respiratory sensitization) may be the best way to proceed for key susceptibilities, but other organizations such as Toxicology Excellence for Risk Assessment have also done excellent work expanding available information when considering occupational exposures.
Second, a unified and ethical approach is needed for identifying relevant susceptibilities in worker populations exposed to agents with known susceptibility factors. While many employers voluntarily work to identify these susceptibilities for the purpose of avoiding risk, leadership is needed from regulatory agencies and organizations that provide insurance and medical guidance. Without such leadership, employers may not adequately consider susceptibility, leading to avoidable illness or disability.
Third, and as always, workers need to be more empowered to understand their personal risk factors and the dynamics of the agents to which they are potentially exposed.
The framework authors believe that the needs for susceptible worker protection will only accelerate given recent trends in medicine and employment dynamics. Now more than ever, OEHS professionals must chart a difficult course through uncertainty and emerging science to share complex information with decision makers. As this new domain evolves, it is important to keep in mind those who may need our protection the most.
SPENCER PIZZANI, CIH, is the occupational health manager for PepsiCo Global EHS. His professional passions include sensor technology, genetic susceptibilities, and accessibility of industrial hygiene technical information.
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AIHA: “Frameworks.”
AIHA: “Technical Framework: Susceptible Worker Protection” (May 2023).
ScienceAdvances: “Psychological Inoculation Improves Resilience Against Misinformation on Social Media” (August 2022).
Sociometry: “The Effectiveness of Supportive and Refutational Defenses in Immunizing and Restoring Beliefs Against Persuasion” (June 1961).