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More than five years after SARS-CoV-2 was first reported, the world has returned almost to normal. The World Health Organization ended the public health emergency of international concern for COVID-19 in May 2023, and CDC declared its public health emergency over shortly afterward. Although people still become ill with COVID-19, some live with symptoms of long COVID, and more than two-thirds of employers now combine remote and in-office work, enough time has passed that the public health implications of the early stages of the pandemic have become clear.

The next disease of global concern may not resemble COVID-19 in all aspects, but analyzing effective strategies and missteps made during the pandemic will put industrial hygienists and policymakers on a stronger foundation. AIHA’s Aerosolized Transmissible Diseases guidance document was created to do exactly that.

David Krause, PhD, MSPH, CIH, FAIHA, is the past chair of the AIHA Indoor Environmental Quality Committee and a contributor to Aerosolized Transmissible Diseases. He told SynergistNOW that he sees it primarily as a public health policy document that looks back on pandemics in the recent past in anticipation of the next outbreak. “Eventually there will be one,” he said. “Maybe it'll be a year. Maybe it'll be 100 years. But we really need to capture the lessons learned and put them down in writing.”

Layering Controls

Aerosol Transmissible Diseases starts out with a brief explanation of the hierarchy of controls. The document then considers the evidence in favor of sick leave policies for employees, mechanical dilution of indoor air, surgical masks and respirators, cleaning and disinfecting surfaces, germicidal ultraviolet radiation, and ASHRAE Standard 241-2023, Control of Infectious Aerosols. The document concludes by outlining evidence-based recommendations for responding to future pandemics.

The guidance document stresses the need to implement multiple controls with complementary strengths and weaknesses, following the Swiss cheese model. “This strategy highlights the significance of utilizing layered control measures,” the document states, “including administrative and engineering controls, alongside PPE like N95 respirators, to establish a more comprehensive and effective approach to mitigate the transmission of infectious agents.”

Krause agreed and emphasized the need to rely on multiple barriers to disease transmission. For example, Krause noted that although ventilation and air filtration are important controls, upgrading building HVAC systems to high levels of performance is costly and takes time. The redesigned system may never even be used as intended. “How do you prepare enough but not over-prepare? How do you manage the cost of that? And how do you ramp up your response?” he said. “I think this document tries to balance those needs, rather than picking one tool and saying, ‘This one tool is the only tool you need, and this is how you should move forward.’”

Contribution by Experts

Effective implementation of controls requires working with industrial hygienists and other experts in preventing occupational illness. “The main points that the document really tries to push are using a multi-tiered approach, relying upon the hierarchy of controls, and looking towards qualified, competent industrial hygienists to guide you on how to implement those controls and protective measures in the future,” Krause continued.

He discussed one of his clients during the pandemic, a university that had paid tens of millions of dollars for an upgraded ventilation system. However, this system was not installed by people with necessary expertise. When Krause inspected the system, he found gaps as wide as six inches between the filters, allowing much of the air to flow into the gap instead of between the filters. The client had spent a great deal of money without receiving the benefits they had anticipated. “Those kind of realizations made me acknowledge industrial hygienists’ verification and validation of all these efforts,” Krause said. “This system could have made a much greater impact than it really did.”

Moreover, Krause felt that although industrial hygienists were sought out by corporate, industrial, and medical employers, their expertise was “underutilized” by public health organizations and government agencies at the federal, state, and local levels. In terms of “broader public policy and communications with the public,” he said, “industrial hygiene was a bit player. And that should change.”

The Aerosolized Transmissible Diseases document emphasizes industrial hygienists’ abilities to identify and mitigate risks associated with airborne contaminants. “These actions comprise the public health contribution of the IH,” the document states, “grounded in good science and engineering, solid communication skills, and effective risk management.”

Creation of New Standards

The guidance document evaluates ASHRAE Standard 241, which was developed at the urging of the White House COVID-19 Response Team and promulgated in 2023. Krause followed this by stressing the need to create improved standards, not only for ventilation but also for other disease transmission controls. For example, the standardized method for certifying air cleaners developed by the Association of Home Appliance Manufacturers addresses allergens such as dust and pollen but not airborne pathogens, Krause observed. Although some studies have found that portable air cleaners may be effective in limiting infectious disease transmission, there is no standard that measures the devices’ performance at this task. “We can recommend that you have a HEPA-filtered air cleaner that provides a certain level of performance,” he said, “but without a certifying agency or body that ensures the consumer is able to tell the difference” between accurate and fraudulent claims by manufacturers.

He noted that disinfectants and cleaning products are supposed to be regulated under the Federal Insecticide, Fungicide, and Rodenticide Act, but enforcement of FIFRA was temporarily suspended during the COVID-19 pandemic. The use of surgical masks for source control should also be tested, and masks should be assigned standardized ratings for effectiveness, Krause suggested. However, the enforcement of even well-established respiratory protection standards will be hindered by the sudden, drastic reductions in force at NIOSH, which began in late March. “I do have concerns,” Krause said, “that the current budget effects we're seeing and the decimation of NIOSH, the only organization that is out there doing certification for respirators, will leave a gaping chasm in our knowledge and the reliability of respirators.”

“We obviously wrote this and completed it long before the current federal efforts to defund public and workplace health and safety programs came to fruition,” he continued. “We find ourselves less prepared, moving into the next pandemic, than we should be. And maybe even less prepared than we were before COVID-19 struck.”

Who Is the Document For?

According to Krause, Aerosolized Transmissible Diseases is intended for two audiences. The first is industrial hygienists and AIHA leadership. For them, the document records successes and failures during the COVID-19 pandemic. Furthermore, Krause felt that the document itself serves as a call for industrial hygienists to reflect on their contributions to the field, particularly since one of the contributors, Ling-Ling Hung, PhD, FAIHA, passed away last February. Krause encouraged industrial hygienists to “ask themselves what they are contributing to the promotion and use of our own profession.”

The document is also for “policy makers and planners for the next pandemic at the state and federal, even local, levels,” Krause said. It is not intended only to help policymakers prepare but to prompt them to take action. He encouraged policymakers to ask themselves what went well, what went wrong, and what lessons they learned from COVID-19.

“We need to take those lessons learned and put them into our plans for preparing for the next pandemic,” he said. “Because if you're not preparing, you're planning to fail.”

The Aerosolized Transmissible Diseases guidance document may be downloaded for free from AIHA’s website.