Formaldehyde Exposure Tied to Cognitive Impairment

Megan Brooks

December 23, 2021

Long-term exposure to formaldehyde on the job is linked to cognitive impairment down the road, new research suggests.

In a large observational study of adults aged 45-70 years, researchers found a 17% higher risk for cognitive problems in those with occupational formaldehyde exposure — and higher risks for those with longer duration of exposure.

"The effect of formaldehyde on the brain has been previously shown mainly in animal experiments, but very few studies have been done on humans," lead author Noemie Letellier, PhD, Institute for Neurosciences of Montpellier, University of Montpellier, France, told Medscape Medical News.

"Our results show that being or having been occupationally exposed to formaldehyde is associated with cognitive impairment in a relatively young population," Letellier said.

The findings were published online December 22 in the journal Neurology.

Dose-Effect Relationship

The investigators assessed a representative sample of 75,322 adults in France (median age, 57.5 years; 53% women). All were part of the CONSTANCES cohort, an observational cohort with a focus on occupational and environmental factors. 

A total of 6026 participants (8%) were exposed to formaldehyde during their careers. Their occupations included nurses, caregivers, medical technicians, workers in the textile, chemistry and metal industries, carpenters, and cleaners.

The researchers calculated lifetime formaldehyde exposure using a French job-exposure matrix created to estimate a person's exposure to potential health hazards in different occupations.

Individuals were divided into three equal groups according to their years of exposure to formaldehyde. "Low" was considered to be 6 or fewer years of exposure, "medium" was 7 to 21 years, and "high" was 22 or more years.

Participants were also split into three groups according to their cumulative exposure (total lifetime formaldehyde exposure based on the probability, intensity, and frequency of exposure).

Prevention Efforts Needed

After adjusting for age, sex, education and other confounders, participants exposed to formaldehyde were at higher risk for global cognitive impairment (adjusted relative risk [aRR], 1.17; 95% CI, 1.1 - 1.2).

Longer duration of exposure and high cumulative lifetime exposure were associated with worse cognitive impairment, "with a dose-effect relationship for exposure duration," the researchers report.

Those exposed to formaldehyde for 22 years or more had a 21% higher risk of global cognitive impairment and workers with the highest cumulative exposure had a 19% higher risk of cognitive impairment compared with workers with no exposure.

Although workers with recent exposure showed higher cognitive impairment, "time may not fully attenuate formaldehyde-associated cognitive deficits, especially in highly exposed but also in moderately exposed workers," the researchers write.

They caution that their findings only show an association and does not prove that exposure to formaldehyde causes cognitive impairment.

Nonetheless, Letellier encourages healthcare providers to "be aware of lifetime occupational exposure to target prevention efforts to the identified occupational groups."

This especially includes the care sector where the most people are exposed to formaldehyde, such as nurses, caregivers, and medical technicians, she added.

"Despite the restrictions on the use of formaldehyde due to the better knowledge of its toxicity, especially its carcinogenic effect, formaldehyde is still widely used in many sectors. These results encourage prevention efforts to further limit worker exposure to formaldehyde," Letellier said.

Relevant to Healthcare Workers

Commenting on the study for Medscape Medical News, Shaheen E. Lakhan, MD, PhD, a neurologist in Newton, Massachusetts, told Medscape Medical News that exposure to some degree of formaldehyde is found in every home and workplace, "from the floors to furniture."

"If you have cigarette smoke in the environment, your exposure rises sharply. When limiting your exposure, it's not only cancer that you are preventing, but also your brain health," added Lakhan, who was not involved with the research.

He said the disturbances in cognitive function noted in the current study were "particularly relevant to healthcare workers, given the use of formaldehyde in sterilization, tissue pathology processing, and embalming."

"Interestingly, with only past exposure, there seems to be some degree of cognitive recovery," but it does not return to a level before any exposure when corrected for age and other factors, Lakhan said.

Some caveats should also be noted, he pointed out. The study included a French population, but regulators such as the US Occupational Safety and Health Administration (OSHA) and the California Office of Environmental Health Hazard Assessment have strict standards on formaldehyde use in a variety of work settings.

On the flip side, given the COVID-19 pandemic, there has been greater use of chemical disinfectants in and out the workplace, some of which contain formaldehyde, Lakhan said.

In addition, he noted the study assessed data from 1950-2018, so pre-pandemic.

"A word of advice from a brain doc: check with your employer on the level of occupational exposure to formaldehyde, heavy metals, and other toxic substances — and cross-reference with your local environmental standards," Lakhan concluded.

The research was supported by a grant from the French Agency for Food, Environmental and Occupational Health & Safety. The investigators and Lakhan have disclosed no relevant financial relationships.

Neurology. Published online December 22, 2021. Abstract

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