08
Nov
Elevated Asthma Risk from Chlorpyrifos and Organophosphates Reported as Court Rolls Back Protections
(Beyond Pesticides, November 8, 2023) A study published in Environmental Science and Pollution Research finds organophosphate pesticides (OPs) are linked to an increased asthma prevalence. The study was released just before an 8th Circuit U.S. Court of Appeals November 3 decision vacating EPA’s 2021 decision to cancel all food tolerances for chlorpyrifos and sending it back to the agency. (Required by a 9th Circuit Court of Appeals decision in April 2021 to take action, EPA issued a final rule in August, 2021—in full effect February 28, 2022—after an earlier 9th Circuit decision, concluding that, “EPA is unable to conclude that the risk from aggregate exposure from the use of chlorpyrifos meets the safety standard of the Federal Food, Drug, and Cosmetic Act (FFDCA). Accordingly, EPA is revoking all tolerances for chlorpyrifos.”
Using urinary metabolites of OPs, the study highlights that diethyl phosphate (DEP, the breakdown chemical of chlorpyrifos) has the strongest association with asthma. However, individual and combined exposure to all OPs have a significant link to respiratory disease. 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. Damage to the respiratory system can cause several issues—from asthma and bronchitis to oxidative stress that triggers the development of extra-respiratory manifestations like rheumatoid arthritis and cardiovascular disease.
Organophosphorus pesticides have a wide range of biological uses—from insecticides to flame retardants—that make these chemicals ubiquitous, significantly contributing to ecosystem contamination. Furthermore, despite organophosphates having less bioaccumulation potential, residues are consistently present in human and animal blood, urine, tissues, and milk. Although research demonstrates that OPs are highly toxic, there remains an inadequate understanding of how OP exposure impacts body systems like the respiratory system. Therefore, the rise in respiratory illnesses and organophosphate use over the last three decades is highly concerning. In light of the recent court decision, the OP study is especially alarming and notes, “These findings underscore the importance of continued efforts to mitigate exposure to OP pesticides and improve respiratory health outcomes for the broader population.”
The study analyzes data from the National Health and Nutrition Examination Survey (NHANES) projects conducted between 2003–2008, 2011–2012, and 2015–2018. Using multiple logistic regressions and restricted cubic spline (RCS) regressions, researchers examined the correlation between urinary OP metabolites dimethyl phosphate (DMP), diethyl phosphate (DEP), dimethyl phosphorothioate (DMTP), and diethyl phosphorothioate (DETP), and asthma prevalence among 9,316 U.S. adults, accounting for individual and combined exposure to OPs. The results find that 1,298 of the 9,316 adults in the study cohort have asthma, with a little over 50 percent female and an average age of 47. The metabolites DMP and DEP have the strongest association with asthma incidents, regardless of whether urinary OP concentrations contain an individual or mixture of metabolites. Moreover, DEP has the highest association with asthma occurrence, eliciting the most substantial effects on respiratory outcomes.
The connection between pesticides and associated respiratory risks is nothing new, as many studies link pesticide use and residue to various respiratory illnesses. Exposure to pesticides from residencies near pesticide processing plants, contact with pesticide-tainted clothes and tools, and households with improper storage and use of pesticides are at greater risk of respiratory illness, including asthma (ranking first) from chronic exposure and upper and lower airway obstruction from acute exposure. Studies find pesticide exposure can trigger asthma and the attacks, as exposure to insecticides before the age of five can increase the risk of asthma diagnosis, with toddlers twice as likely to become asthmatic. Furthermore, Significant disparities in asthma morbidity and mortality disproportionately impact low-income populations, people of color, and children living in inner cities.
Agricultural workers and their families are at the most significant risk from these health hazards. Working throughout one’s lifetime increases the risk of asthma, Chronic Obstructive Pulmonary Disease (COPD), and other respiratory issues. A 2016 study linked an astounding 78 pesticides to allergic and non-allergic wheeze among male farmers. Agricultural work with toxic pesticides was associated with an increased risk of the potentially deadly diseases idiopathic pulmonary fibrosis (IPF) in a 2021 study and chronic obstructive pulmonary disease (COPD) in a recent February 2022 report. Unsurprisingly, a comprehensive literature review published in 2020 finds pesticide exposure strongly correlated with the development of respiratory diseases.
Beyond Pesticides has reviewed the particular exposure risks farmworkers endure and health outcomes; for example, agricultural (and other) workers exposed to pesticides and other contaminants are at increased risk of developing a lung condition known as idiopathic pulmonary fibrosis. The risk of developing Farmer’s lung—a common allergic disease induced by inhaling biological dust and a contributor to respiratory morbidity among farmers— also increases with pesticide exposure. Thus, chronic inhalation of agriculture-related dust (e.g., particulates from grains, feed, soils, and biological aerosols from plant and animal matter that may harbor synthetic pesticide and fertilizer residues) can increase airway inflammatory diseases, including asthma, chronic bronchitis, and COPD. The particulates in dust play a part in disease development, but so, too, do the various microbiota that may be part of a dusty agricultural environment. A disruption of the homeostasis of the human microbiome (known as dysbiosis) can increase the risk of asthma and other respiratory diseases. In addition, pesticide exposures can alter the gut microbiome, which mediates a significant portion of the human immune response.
Many researchers, including those on this study, suggest an increase in environmental pollutants like pesticides may be responsible for the influx of respiratory diseases. The risk of asthma is seasonal, with the spring having greater incidents due to the influx of pesticide use during this period. Moreover, those handling pesticides without protective equipment have a much greater risk of developing asthma after exposure. A University of California, Berkeley study found that the general exposure to organophosphates (not only chlorpyrifos) corresponds with a measurable decrease in lung function. Prolonged exposure (over 56 days) to the insecticide chlorpyrifos more than doubles the risk of developing lung cancer.
This study assesses the impacts of OP compounds on individuals with asthma, highlighting the positive association between the presence of metabolites in urine and the occurrence of asthma. Although the study notes the mechanisms involved in OP-induced asthma are unclear, previous studies report OPs to inhibit the enzyme acetylcholinesterase, or AChE, impacting smooth muscles in the airway and nerves in the respiratory system. The suggestion of multiple mechanisms involved in OP-induced asthma highlights the significant influence OPs have on respiratory pathology. OPs are cholinesterase inhibitors, which means they bind to receptor sites for AChE, essential to standard nerve impulse transmission. In affixing to these receptor sites, cholinesterase inhibitors inactivate AChE and prevent the clearing of acetylcholine. The buildup of acetylcholine can lead to acute impacts, such as uncontrolled, rapid twitching of some muscles, paralyzed breathing, convulsions, and, in extreme cases, death. The compromise of neural transmission can have broad systemic impacts on the function of multiple body systems, including the respiratory system.
In the U.S., over 25 million people live with asthma. The increasing rate of respiratory pathology since the 1980s demonstrates a need for better environmental policies and protocols surrounding contaminants like pesticides. Considering respiratory diseases represent a significant health issue for agricultural workers—who often experience pesticide exposure at higher rates due to occupation—it is essential to understand the association between pesticide exposure and respiratory pathology or the study of causes and effects of respiratory diseases. Furthermore, with a new report finding an association between air pollution and higher death rates (9%) related to SARS-CoV-2 (COVID-19), global leaders must eliminate excessive pesticide use to mitigate respiratory diseases’ impacts on human health. Policies should enforce stricter pesticide regulations and increase research on the long-term impacts of pesticide exposure. Beyond Pesticides tracks the most recent 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 pesticides, see PIDD pages on asthma/respiratory effects and other diseases. Learn more about how inadequate pesticide use regulations, including organophosphates, can adversely affect human and environmental health; see Beyond Pesticides’ Pesticides and You article “Highly Destructive Pesticide Effects Unregulated.”
Beyond Pesticides advocates a precautionary approach to pest management in land management and agriculture by transiting to organic. Buying, growing, and supporting organic can help eliminate the extensive use of pesticides in the environment and from your diet. For more information on how organic is the right choice for consumers and the farmworkers who grow our food, see the Beyond Pesticides webpage, Health Benefits of Organic Agriculture. Removing pesticides from parks that disproportionately affect people of color in the community and as landscapers. Help convert your parks, playing fields, and schoolyards to organic land management through Beyond Pesticides’ Parks for a Sustainable Future program.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Environmental Science and Pollution Research
