Some Environmental Pollutants Increase Risk of COVID-19

In the last three-plus years, scientists have discovered multiple explanations for the wide variation SARS-CoV-2 presents with—be that why it infects one person but not another, or why one patient lands in the hospital while another just has a headache.

Researchers have linked biomarkers, genes, microbiome, olfactory cells and more to the infection and onset of severe COVID-19. Still, the question as to why some people get infected and others don’t is largely unexplained—or at least some pieces of the puzzle are missing.

Now, Spanish scientists say they have found one such puzzle piece that may help further explain—specific chemical pollutants.

In the first prospective study of its kind, researchers show that high levels of certain chemical pollutants in the blood are associated with an increased risk of SARS-CoV-2 infection and COVID-19 disease.

For the study, published in Environmental Research, the team tested 154 frozen blood samples collected in 2016 for numerous environmental chemicals. Then—in the same individuals—the team collected samples from and examined the relation between environmental chemicals in the blood and the frequency of SARS-CoV-2 infection during the pandemic years 2020 and 2021, taking into account personal habits and living conditions at the time.

Overall, the researchers tested 112 compounds, including persistent organic pollutants (POPs) and 20 rare earth elements.

The findings reveal that people with higher blood levels of certain pollutants had a higher risk of both becoming infected with and developing SARS-CoV-2.

Among POPs, DDD and DDE—derivatives of the Silent Spring-famed pesticide DDT—were associated with a higher risk of developing COVID-19. On the chemical side, lead, thallium, manganese, aluminum and ruthenium were significantly associated with COVID-19. Additionally, high levels of thallium, ruthenium, lead and gold, were associated with a higher risk of infection.

Significantly, a number of mixtures of up to five agents were identified with all substances associated to a positive risk of SARS-CoV-2 infection and COVID-19 development. In most mixtures, the substances belonged to several different chemical groups.

“This finding is remarkable in itself, and suggests that mechanistic, clinical, and epidemiological studies are really warranted to refute or to expand our findings,” the study authors write. “The results should encourage translational research from the observations we made in a real human population to the clinic and the laboratory.”

In data the team calls “reassuring,” historically or currently prevalent immunoactive substances, such as polychlorinated biphenyls (PCBs) and most POPs were weakly or not associated with COVID-19 or seropositivity, including arsenic, cadmium, mercury and zinc.

“These [results] are important for clinical and public health reasons,” write the researchers. “For example, zinc supplementation has been hypothesized—but so far failed to prove—to be effective for the prevention and treatment of COVID-19. In medicine, factors that influence risk of infection, incidence of the disease, severity and the clinical course are often different.”

Meanwhile, the study results showed high levels of iron and selenium played a protective role against infection with SARS-CoV-2.

The study authors emphasize more research into the topic is needed, as the environmental agents in their study may influence immune processes and other disease attributes.

“Several of [the identified] pathways overlap with those involved in the host response to the SARS-CoV-2 virus and may contribute to explain the observations we report. The contaminants we analyzed are also risk factors for numerous diseases that increase susceptibility to or worsen the course of SARS-CoV-2 infection,” conclude the study authors.