A review published in Food and Chemical Toxicology suggests organophosphorus pesticides (OPs) may increase the ability of SARS-CoV-2 to cause COVID-19, especially among vulnerable individuals with underlying medical conditions. Organophosphorus pesticides (OP) have a wide range of biological uses that makes these chemicals ubiquitous, significantly contaminating both terrestrial (land) and aquatic (water) environments.

However, OPs are highly toxic, originating from the same compounds as World War II nerve agents. Moreover, OPs are one of the leading causes of poisoning globally. Therefore, it is vital to understand how OPs exposure will impact human health in conjunction with other immunologically compromising diseases like COVID-19.

Considering COVID-19 and OP exposure act similarity on the respiratory system, exacerbating adverse inflammatory responses, reviews like these highlight the significance of evaluating synergism between diseases and toxic chemicals to safeguard human health. Researchers in the study note, “To curb SARS-CoV-2 infection, a healthy immune system is obligatory despite potent vaccine to alleviate morbidities in patients.

But unintentional exposure to OP compounds from several sources can rupture the antiviral defense against SARS-CoV-2. Moreover, respiratory ailments may also be fueled by OP compounds. Hence, SARS-CoV-2 mediated morbidities and fatalities could be backed by unintentional exposure to OPs in patients.”

Amidst the outbreak of SARS-CoV-2 (COVID-19), the global demand for pesticides, including disinfectants and sanitizers, has increased substantially as a means of preventing illness in domestic and community settings. Additionally, the increasing pervasiveness of moist environments from severe weather events like hurricanes increases the amount of mold and mosquito pests in some areas, causing higher inputs of fungicides and insecticides to combat the issue.

However, exposure to these toxic pesticides can weaken the body’s immune response to illnesses, creating an environment for underlying conditions (like respiratory issues such as asthma or endocrine disruption problems like diabetes) to flourish among vulnerable individuals.

In this review, researchers examine the structure, transmission-pattern, and respiratory immune response associated with SARS-CoV-2. Additionally, researchers inspect OP exposure impacts on humans and animals using a combination of in vivo and in vitro studies. Lastly, the review investigates the benefits of antioxidants and co-exposure to SARS-CoV-2 and OP compounds as a means of mitigating disease causes and effects.

The immune system offers the best defense against coronavirus-infection, as the virus stimulates an innate and adaptive immune response to expel viral particles from the body. Innate immune responses are the first line of defense against viral infections, activating myeloid immunocytes (cells that mediate immune responses against pathogens). These mediating cells create antibodies that the complement system (a network of proteins that eliminate pathogens) enhances. Therefore, review researchers speculate immunocytes and the complement system can restrict coronavirus-infections. However, coronavirus infections can suppress/delay interferon (INF) protein synthesis responsible for defending against viral infections, causing a lapse in the innate defense system.

Similarly, an adaptive immune response involves various immune cells and antibodies essential to protect against coronavirus infections. Still, injury to cells responsible for safeguarding against viral infections can induce more severe disease progression, immunocompromising the respiratory system of COVD-19 patients.

OP compounds are immunotoxicants. They modify the structure of lymphoid organs responsible for immunocyte cell production, causing injury and alteration to the cells. Additionally, these compounds lower antibody concentration and reduce autoimmune response to stimuli. The review finds current OPs, including chlorpyrifos and malathion, induce oxidative stress and DNA damage in immune system blood cells, similar to one of the most toxic, restricted OPs, methyl parathion.

Furthermore, OPs can disrupt the homeostasis of proinflammatory and anti-inflammatory responses of cytokine proteins like INF responsible for immune protection.

This review demonstrates many immunotoxic similarities between OP exposure poisoning and coronavirus. Both OPs and coronavirus attack the immune system impacting immune cell concentrations (via death or injury), altering immune protein function and response, and dampening autoimmune reaction. Similarly, coronavirus and OP exposure predominantly impact respiratory capacity, causing various ailments that can lead to respiratory failure.

Although coronavirus can induce other adverse immunological outcomes, such as cardiac dysfunction, gastrointestinal issues, kidney damage, and dermal reactions, studies find OP exposure can have similar adverse multi-organ effects. Therefore, co-exposure to OPs and coronavirus can exacerbate disease effects in COVID-19 patients, with additional exposure to OPs intensifying inflammatory response and respiratory issues that can lead to death.

COVID-19 is a systemic (general) disease that overwhelmingly impacts the respiratory system of many patients. The respiratory system is essential to human survival, regulating gas exchange (oxygen-carbon dioxide) in the body to balance acid and base tissue cells for normal function. However, damage to the respiratory system can cause a plethora of issues — from asthma and bronchitis to oxidative stress that triggers the development of extra-respiratory, systemic manifestations like rheumatoid arthritis, and cardiovascular disease.

Furthermore, underlying medical conditions (i.e., heart/kidney disease, diabetes, cancer, high blood pressure, obesity, etc.) heighten risks associated with severe illness from disease, including COVID-19.

Exposure to organophosphate pesticides (i.e., chlorpyrifos, malathion, diazinon, etc.) can heavily influence the respiratory system. Studies link pesticide use and residue to various respiratory illnesses. Organophosphates produce adverse effects on the nervous system, having the same mode-of-action as nerve agents for chemical warfare.

Chemical exposure can cause a buildup of acetylcholine (a chemical neurotransmitter responsible for brain and muscle function) that can lead to acute impacts, such as uncontrolled, rapid twitching of some muscles, paralyzed breathing, convulsions, and, in extreme cases, death. The compromise of nerve impulse transmission can have broad systemic impacts on the function of multiple body systems. In addition to being highly toxic to terrestrial and aquatic organisms, human exposure to organophosphates can induce endocrine disruption, reproductive dysfunction, fetal defects, neurotoxic damage, and kidney/liver damage.

Although most OP uses in the U.S. are agricultural, toxicity experts recommend a ban on all OP uses as the Environmental Protection Agency (EPA) and World Health Organization consider more than 40 OPs that are moderately or highly hazardous to human health. States, including Hawaii, California, New York, and Maryland, plan to phase out chlorpyrifos use in agriculture following evidence of neurotoxic effects on children.

However, other OPs remain in use despite their notorious toxicity. EPA classifies some commonly used OPs like malathion, a popular mosquito control, and tetrachlorvinphos, a common flea and tick killer in pet collars and shampoos, as probable carcinogens. Therefore, OPs remain a human health risk in conjunction with respiratory distress commencing from diseases like COVID-19, especially to individuals with underlying medical conditions.

This review reinforces evidence that OP exposure can compromise immune function against viral infections. A healthy immune system is vital to overcome coronavirus infections. However, exposure to OPs before, during, and possibly after coronavirus infections may promote adverse respiratory function and inflammatory responses in patients. Moreover, researchers suggest OP-induced immune cell death from oxidative stress may reduce vaccine effectiveness due to the lack of antibodies.

The review researchers conclude that world leaders should investigate potential augmented interactions (synergism) between OPs and deadly viral pathogens like coronavirus to protect human health:

“Since direct experimental works dissecting the collaborative impacts of OPs and SARS-CoV-2 are still lacking, this review will attract the scientific community across the planet to concentrate on the proposed hypothesis to unveil the synergism between the two threats to the human race. Serious health problems discussed in the review will also draw attention of global environmental policymakers and concerned government/non-government organizations toward the perilous impacts of OP exposure in humans. Alongside, it will insist them to adopt necessary resolutions and amend policies that could limit human contacts with OPs.”

As the U.S. COVID-19 cases continue to rise, there is an urgent need to evaluate the effect pesticide exposure and uses have on health outcomes of disease. Although some practices and products can prevent coronavirus infections, the continued use of toxic pesticides in the surrounding environment increases disease risk factors. Pesticide use should not allow harm to those disproportionately affected by these chemicals, including people of color, essential workers, and farm/landscape workers who may suffer elevated rates of exposure to the virus.

Advocates maintain individuals and government officials alike should assess all risks associated with pesticide use, including the mode of action. However, EPA’s failure to respond to current science is a significant shortcoming of its risk assessment process, especially regarding disease implications.

Beyond Pesticides tracks the most recent health studies related to pesticide exposure through our Pesticide-Induced Diseases Database (PIDD). This database supports the clear need for strategic action to shift away from pesticide dependency.

For more information on the multiple harms of pesticide exposure, see PIDD pages on asthma/respiratory effects, cancer, endocrine disruption, and other diseases. Additionally, learn how to protect yourself from COVID-19 safely by visiting Beyond Pesticides’ webpage on Disinfectants and Sanitizers for more information.

Beyond Pesticides advocates a precautionary approach to pest management in land management and agriculture by transitioning to organic. Learn more about how the lack of adequate pesticide use regulations, including organophosphates, can impact human and environmental health using Beyond Pesticides’ Pesticides and You article “Highly Destructive Pesticide Effects Unregulated.”

Originally published by Beyond Pesticides.