08
Mar
Study Provides First Combined Assessment of Multiple Classes of Pesticides in Human Blood
(Beyond Pesticides, March 8, 2024) A major problem has vexed pesticide regulators and researchers for decades: Humans and other organisms almost always have multiple pesticides in their bodies, but techniques for assessing their combined effects, or cumulative body burden from multiple chemical classes are not typically available. A new study from Chinese and British researchers provides the first combined assessment of multiple classes of pesticides in human blood. The authors believe they are the first to develop a way to quantify multiple types of pesticides in human serum (clear liquid part of blood) as opposed to urine or from other sample collection methods. This is a tool that authors say is a more accurate way of assessing the real world exposure and ultimately the adverse impact of pesticide use on human health.
The researchers had a small sample of 31 men and 34 pregnant women in Wuxi, China. They chose 73 pesticides and a few of their breakdown products to identify from three categories: fungicides, neonicotinoid insecticides, and triazine herbicides. Their testing protocol confirms their expectation that food—primarily produce—is the major source of pesticide exposures. This result reinforces Beyond Pesticides’ mission of supporting the shift in agriculture to pesticide-free methods and regenerative practices. Eating organic food is the most effective way to reduce the body burden of pesticides.
The researchers detect a total of 40 pesticides and 10 related chemicals in the sample. No sample was free of all pesticides. More than 80 percent contained more than 10 pesticides. The researchers note that this adds to the evidence that pesticides are ubiquitous in human bodies. As Beyond Pesticides often stresses, it defies belief that these chemicals could have no effect on human (and ecosystem) health.
Based on the sampling data, the team calculates each subject’s estimated daily intake (EDI) of each pesticide, adding those together to find a cumulative EDI. They then compare the EDI with acceptable daily intake (ADI) standards for each pesticide set by various countries and international organizations, including the U.S. Environmental Protection Agency (EPA) and the World Health Organization. ADI is an estimate of how much of a substance a person could consume daily over a lifetime without suffering adverse health effects. Then they derive a cumulative hazard quotient (HQ), which is an estimate of the health effects resulting from exposures above the ADI.
Of the three pesticide categories, fungicides occurr most often and at the highest levels. Boscalid, a carbamid compound, is the most common fungicide in the samples. Upon its registration in 2003, EPA described it as “practically nontoxic.” But it inhibits succinate dehydrogenase (SDH) a chemical whose structure and functions, in the words of one review, are highly conserved in “nearly all extant eukaryotes”—that is, everything but bacteria and their unicellular cousins, the archaea. Therefore, what it does to one organism it may very well do to all (including humans). Studies in zebrafish show unambiguously that boscalid affects central nervous system development and function and glucose metabolism, causes oxidative stress, and disrupts reproductive hormones.
Four of the fungicides are triazoles, which the authors note can cross the blood-brain barrier and infiltrate cerebrospinal fluid. The current study is the first to find them in human serum. Triazoles affect a steroid synthesis pathway in fungi that is the same in humans. Triazoles are known to damage cardiac tissue and trigger oxidative stress in rats.
Simazine is the most common triazine herbicide in the samples. The triazine family includes the notorious endocrine disrupter atrazine; simazine is used for weed control in fruit and nut orchards, berry fields and cornfields, and aquatic environments. EPA regulates simazine according to its similarity to atrazine. It was approved in 1972 for algae control in swimming pools, hot tubs and whirlpools until 1994, when EPA withdrew this registration based on “unacceptable cancer and non-cancer health risks to children and adults.” However, by 2022, EPA declared in a rule establishing tolerances for certain crops that “cancer risk is not a concern and a quantitative cancer risk was not conducted.” Researchers have found effects of simazine on the hypothalamic-pituitary-gonadal axis leading to, for example, “constant estrus [in heat]” and “continuous estrogen stimulation of mammary gland” in female rats. Endocrine disruption is a well-established factor in the development of many cancers.
Neonicotinoids are widely recognized to be neurotoxic to many beneficial insects such as bees as well as humans, but they may also have other harmful effects, including disruption of metabolic functions involving lipids and leading to obesity and cardiovascular disease. A previous study in Wuxi by different researchers identified nine neonicotinoids in human serum along with nine lipids already known to be affected by environmental contaminants, including dioxins, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and organophosphorus flame retardants. The authors of the current study found eight neonicotinoids in their samples, three of which had not been observed in human serum before. They also observed that, like some fungicides, neonicotinoids can cross the blood-brain barrier.
The authors found that there is a clear linear relationship between maximum residue levels allowed in foods, also called tolerances, and the serum levels of pesticides in their study subjects—the higher the allowable residue in food, the higher the serum level of that pesticide. This means that setting these tolerances lower or eliminating them altogether would go a long way toward reducing pesticide exposures, as would better monitoring and enforcement of such regulations in the U.S., especially on imported foods.
One important aspect of the current study is the identification of numerous troubling pesticides not previously found in human serum, findings that adds to the urgency of further investigation. But the study did not directly demonstrate that any of the pesticides they analyzed are causing adverse health effects. The study’s main significance is that it establishes a method for measuring, comparing, and determining cumulative levels of numerous pesticides in human serum. This method can help determine the extent and severity of those pesticides’ consequences individually and cumulatively.
Perhaps unintentionally, the study also highlights the inadequacy of methods calculating exposures and health hazards using the crude estimates of EDI, ADI, HQ and maximum residue levels/tolerances. These concepts are imprecise almost to the point of “hand waving.” They rest on the assumption that there are some levels of pesticides in the body that are harmless—which, even if true, fails to account for the total risks and hazards presented by the ubiquitous body burdens of multiple pesticides. The most rational course to protect humans and ecosystems from pesticide exposures is to switch agriculture to organic methods as soon as possible. For more on the public health outcomes linked to pesticide exposure, see Beyond Pesticides’ Pesticide-Induced Diseases Database.
All unattributed positions and opinions in this piece are those of Beyond Pesticides
Sources:
Exposure levels and health implications of fungicides, neonicotinoid insecticides, triazine herbicides and their associated metabolites in pregnant women and men. Nanxiu Shang, Yingying Yang, Yilin Xiao, Yukang Wu, Kaixuan Li, Xiaoman Jiang, Edmond Sanganyado, Qing Zhang, Xinghui Xia, Environmental Pollution, Volume 342, 1 February 2024. https://www.sciencedirect.com/science/article/abs/pii/S0269749123020717
A comprehensive review of 1,2,4-triazole fungicide toxicity in zebrafish (Danio rerio): A mitochondrial and metabolic perspective. Tao Huang, Haibo Jiang, Yuanhui Zhao, Jia He, Hongguang Cheng, Christopher J. Martyniuk, Science of The Total Environment 2022. https://www.sciencedirect.com/science/article/pii/S0048969721062550
Biomonitoring and risk assessment of human exposure to triazole fungicides panel. Luiz P.A. Marciano, Luiz F. Costa, Naiane S. Cardoso, Josiane Freire, Fernando Feltrim, Geovana S. Oliveira, Fernanda B.A. Paula, Alessandra C.P. Silvério, Isarita Martins, Regulatory Toxicology and Pharmacology, Volume 147, February 2024. https://www.sciencedirect.com/science/article/pii/S0273230024000060
Serum concentrations of neonicotinoids, and their associations with lipid molecules of the general residents in Wuxi City, Eastern China. Qianyu Chen, Yayun Zhang, Jianhua Li, Guanyong Su, Qi Chen, Zhen Ding, Hong Sun, Journal of Hazardous Materials, Volume 413, 5 July 2021
See Beyond Pesticides info:
Disproportionate Risks: The Effects of Pesticide Exposure Among the Population. https://www.beyondpesticides.org/resources/disproportionate-risks/overview
Read More on Beyond Pesticides’ Agricultural Justice Page. https://www.beyondpesticides.org/programs/agricultural-justice
Pesticide-Induced Diseases: Body Burden. https://www.beyondpesticides.org/resources/pesticide-induced-diseases-database/body-burden
Of Note During Organic Month, Study Finds Organic Diet and Location Affect Pesticide Residues in the Body. https://beyondpesticides.org/dailynewsblog/2023/09/of-note-during-organic-month-study-finds-organic-diet-and-location-affect-pesticide-residues-in-the-body/
