Human Health Risk Assessments – What do they tell us about mosquito control?
Keira J. Lucas, PhD
Deputy Executive Director
Since the rise of the modern environmental movement, concerns about synthetic pesticides, especially the widespread use of DDT to control mosquitoes, have made many people understandably cautious about pesticide use. This caution makes sense!
While the Green Revolution helped boost global food production and played a key role in reducing mosquito-borne diseases, it also came with unintended consequences. The heavy use of synthetic pesticides led to a range of environmental problems, from harming wildlife to contaminating soil and water.
The growing environmental awareness sparked by Rachel Carson’s landmark book Silent Spring shined a light on these issues and inspired lasting change. In response, the U.S. Environmental Protection Agency (EPA) was established to protect human health and the environment, ensuring that pesticides and other chemicals are used safely and responsibly.
How Regulators and Scientists Ensure Safety
The EPA carefully studies pesticides before deciding whether they can be used. Their goal is simple: to make sure people and the environment stay safe. To do this, the EPA runs what’s called a risk assessment, which is a detailed safety check that estimates how likely it is for someone to be harmed by a pesticide and under what conditions. Scientists review all available research and data about each pesticide, including how it’s made, how it’s proposed to be used, and how it might affect people, animals, and the environment.
Essentially, this process determines how and where a product can be used. The EPA may update these rules and restrictions as new scientific data becomes available during the reregistration process, ensuring that decisions stay up to date with the latest information.
In addition to the EPA’s work, many independent scientists, academic partners, and end users further build on these risk assessments. They study how these products perform in real-world conditions, adding another valuable layer of information. This helps ensure that decisions about pesticide use are based on both scientific testing and practical experience.
If the EPA finds that a pesticide could pose a significant risk, they act to reduce it by changing where or how the product can be used. And if a pesticide still doesn’t meet safety standards, even after changes, the EPA will not approve it for use at all.
Why Mosquito Control is Different
Some residents cite studies involving agricultural or occupational pesticide exposure as evidence that mosquito control poses serious risks. Indeed, some of these studies are concerning, such as research linking certain agricultural uses of pesticides to neurological effects, including potential impacts on Parkinson’s disease (Paul et al. 2023).
However, it’s important to understand that mosquito control applications for adult mosquitoes differ dramatically from agricultural or household pesticide use:
When applied correctly, mosquito control products are not considered a significant health risk. Multiple independent studies have consistently shown that potential exposures are well below EPA safety thresholds (CDC, 2005; Peterson et al., 2006; Duprey et al., 2008; Schleier et al., 2009; Macedo et al., 2010; Preftakes et al., 2011; Schleier et al., 2016; Mendoza et al., 2023; Tai et al., 2025; Mendoza et al., 2025). To date, no negative health effects have been linked to mosquito control operations—whether conducted from the ground or by air.
What Recent Research Shows
A comprehensive review of scientific literature published between 2000 and 2024 examined potential human health effects associated with organophosphate use for mosquito control in the United States and Canada (Tai et al., 2025). The review found no evidence that exposure to organophosphates from mosquito control activities is linked to illness, increased hospitalizations, or toxic effects.
A recent human health risk assessment examined how much people might be exposed to naled (Dibrom) during aerial mosquito control applications (Mendoza et al. 2025). Researchers used computer models to estimate how much of the chemical could reach people on the ground after a mosquito control treatment. They based their calculations on an average adult (172 pounds) and a child (22 pounds) who might be in the area for two hours during the application. The results showed that the amount of naled a person might be exposed to is much lower than the safe limit set by the EPA. Adults would receive about 2.5% and children about 14.7% of the EPA’s daily safety level. In simple terms, this means that people’s exposure to naled during normal mosquito control operations is very low and well within safety limits.
Human biomonitoring studies back this up. For instance, aerial applications of pyrethrins in Sacramento County (CA) during the 2005 West Nile virus response did not lead to increased emergency room visits or respiratory, stomach, skin, eye, or neurological problems after treatments (Geragthy et al. 2013). Similarly, during Miami-Dade County’s Zika outbreak, widespread aerial naled applications were not associated with any cases of human poisoning (Mulay, 2018). Other studies that analyzed urine samples before and after truck and aerial pesticide applications also found no increase in pesticide levels (CDC 2005, Duprey et al., 2008). Similarly, Collier County has never recorded a pesticide poisoning related to mosquito control treatments.
Respecting Resident Concerns
Some residents may feel that any level of exposure to chemical pesticides is unacceptable, regardless of the EPA’s established safety limits or scientific risk assessments. These concerns often stem from perceived risks, which can differ from the actual risks identified by scientific studies. Out of respect for these concerns, the District provides advance treatment notifications so residents who wish to take extra precautions have the opportunity to do so before mosquito control treatments take place. These extra precautions help reduce exposure even further, and might include:
In Summary
Modern mosquito control relies on science, regulation, and transparency. EPA and state oversight, decades of safety data, and local accountability ensure that these operations protect both public health and the environment. When used correctly, mosquito control pesticides remain safe (CDC 2005, Peterson et al. 2006, Duprey et al. 2008, Schleier et al. 2009, Macedo et al. 2010, Preftakes et al. 2011, Geragthy et al. 2013, Schleier et al. 2016, Mendoza et al. 2023, Tai et al. 2025, Mendoza et al. 2025) and effective (Lothrop et al. 2007, Carney et al. 2008, Macedo et al. 2010, Hart et al. 2024 ) for reducing mosquito populations. And adult control is most effective as part of an integrated mosquito management program (Wilke et al, 2021).
To sign up for advance treatment notifications, please visit our website here: https://cmcd.org/treatment-notifications/
To learn more about our control materials, please visit our website here: https://cmcd.org/science/history/control-materials/
*PLEASE NOTE*: If you believe you’ve been exposed to a pesticide or are experiencing symptoms of pesticide poisoning, take action immediately. Call 911 for emergencies or contact the Florida Poison Information Center at 1-800-222-1222 for expert guidance. For more information on pesticide poisoning, please visit: https://www.floridahealth.gov/environmental-health/pesticide-poisoning/index.html
References
Carney RM, Husted S, Jean C, Glaser C, Kramer V. 2008. Efficacy of aerial spraying of mosquito adulticide in reducing incidence of West Nile virus, California, 2005. Emerg Infect Dis. 14: 747-54.
Centers for Disease Control and Prevention [CDC]. 2005. Human exposure to mosquito-control pesticides – Mississippi, North Carolina, and Virginia, 2002 and 2003. Morb. Mortal. Wkly. Rep. 54: 529–532.
Duprey Z, Rivers S, Luber G, Becker A, Blackmore C. Barr D, Weerasekera G, Kieszak S, Flanders WD, Rubin C. (2008) Community aerial mosquito control and naled exposure. J Am Mosq Control Assoc. 24: 42-6.
Environmental Protection Agency [EPA]. 2015. Introduction to Pesticide Labels. Accessed: August 11, 2025. Website: https://www.epa.gov/pesticide-labels/introduction-pesticide-labels
Environmental Protection Agency [EPA]. 2021. Naled for Mosquito Control. Accessed: August 11, 2025. Website: https://www.epa.gov/mosquitocontrol/naled-mosquito-control
Geraghty EM, Margolis HG, Kjemtrup A, Reisen W, Franks P. 2013. Correlation between aerial insecticide spraying to interrupt west nile virus transmission and emergency department visits in Sacramento County, California. Public Health Rep. 128: 221-30.
Hart JD, Pandolfi A, Jones T, Jenkins DG. 2024. Ground-Based Pyrethroid Adulticides Reduce Mosquitoes But Not Nontarget Insects in Central Florida. J Am Mosq Control Assoc. 40:125-136.
Lothrop H, Lothrop B, Palmer M, Wheeler S, Gutierrez A, Gosmi D, Reisen W. 2007. Evaluation of pyrethrin and permethrin ground ultra-low volume applications for adult Culex control in rural and urban environments of the Coachella Valley of California. J Am Mosq Control Assoc. 23: 190-207.
Macedo PA, Schleier JJ III, Reed M, Kelly K, Goodman GW, Brown DA, Peterson RKD. 2010. Evaluation of efficacy and human health risk of aerial ultra-low volume applications of pyrethrins and piperonyl butoxide for adult mosquito management in response to West Nile virus activity in Sacramento County, California. J Am Mosq Control Assoc. 26: 57-66.
Mendoza DL, Peterson RKD, Bonds JAS, White GS, Faraji A. 2023. Are adult mosquito control products (adulticides) harmful? A review of the potential human health impacts from exposure to naled and dichlorvos (DDVP). Pollutants. 3: 603-615.
Mendoza DL, Bibbs CS, Dewsnup MA, Rochlin I, White GS, Bonds JAS, Peterson RKD, Faraji A. 2025. Evaluating human health risk of aerial ultra-low volume insecticide applications for adult mosquito management. J ASABE. 68: 753-760.
Mulay PR. 2018. Utilization of syndromic surveillance to identify naled-related illness in Florida.Online Journal of Public Health Informatics, 10(1).
Occupational Safety and Health Administration [OSHA]. 2012. Hazard Communication Standard: Safety Data Sheets. Available at: https://www.osha.gov/sites/default/files/publications/OSHA3514.pdf
Paul KC, Krolewski RC, Moreno EL, Blank J, Holton KM, Ahfeldt T, Furlong M, Yu Y, Cockburn M, Thompson LK, Kreymerman A, Ricci-Blair EM, Li YJ, Patel HB, Lee RT, Bronstein J, Rubin LL, Khurana V, Ritz B. 2023. A pesticide and iPSC dopaminergic neuron screen identifies and classifies Parkinson-relevant pesticides. Nature Communications. 14: 2803.
Peterson RKD, Macedo PA, Davis RS. 2006. A human-health risk assessment for West Nile virus and insecticides used in mosquito management. Environ Health Perspect. 114: 366-372.
Preftakes CJ, Schleier JJ III, Peterson RKD. 2011. Bystander Exposure to Ultra-Low-Volume Insecticide Applications Used for Adult Mosquito Management. Int J Environ Res Public Health. 8: 2141-2152.
Schleier JJ III, Macedo PA, Davis RS, Shama LM, Peterson RKD. 2009. A two-dimensional probabilistic acute human-health risk assessment of insecticide exposure after adult mosquito management. Stoch. Environ. Res. Risk Assess. 23: 555–563.
Schleier JJ III, Marshall LA, Davis RS, Peterson RKD. 2015. A quantitative approach for integrating multiple lines of evidence for the evaluation of environmental health risks. PeerJ. e730.
Tia Z, Connelly CR, Lange SK, Foley N, Rivera JDL, Lazano S, Nett RJ. 2025. A scoping review to determine if adverse human health effects are associated with use of organophosphates for mosquito control. J Med Entomol. 62:8-18.
Wilke ABB, Vasquez C, Carvajal A, Ramirez M, Cardenas G, Petrie WD, Beier JC. 2021. Effectiveness of adulticide and larvicide in controlling high densities of Aedes aegypti in urban environments. PLoS One. 16: e0246046.
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Dr. Keira Lucas serves as the Deputy Executive Director of the Collier Mosquito Control District, bringing a background in vector biology. She specializes in mosquito reproduction and biology, integrated pest management and pesticide resistance management, with experience in applying science-based strategies for effective and sustainable mosquito control.
