3 November 2020

Pesticides Contribute to Infectious Disease Prevention and Public Health

S. Eliza Halcomb, MD, FACMT

Medical Sciences and Outreach Lead
Bayer U.S. Crop Science

By S. Eliza Dunn (Halcomb), MD, FACMT

The greatest public health achievement of the 20th century is a 30-year increase in life expectancy. Never before has the human population achieved such a milestone. Several simple interventions contributed significantly to this unprecedented advance: the introduction of vaccines, antibiotics, water sanitation and surprisingly, pesticides. While the first three are frequently credited with revolutionizing the prevention and management of infectious diseases, the contribution of pesticides is often overlooked. Pesticides not only prevent the transmission of vector-borne illness in people, but also significantly improve food security by preventing insect-borne diseases in plants and crop loss due to weed infestations. The overwhelming scientific consensus is that all these interventions have decreased diseases and deaths around the world. Unfortunately, recent unscientific and sensationalized claims are reversing this positive trend. For the first time in decades, we are witnessing a backslide due to systematic dismantling of these public health advances.

Pesticides not only prevent the transmission of vector-borne illness in people, but also significantly improve food security by preventing insect-borne diseases in plants and crop loss due to weed infestations.

Insect-Borne Health Threats

According to the World Health Organization (WHO), insect-borne illness is responsible for over 700,000 deaths annually worldwide. Malaria infects over 219 million people every year and with global warming, novel diseases spread by the invasive Aedes mosquito have been emerging in areas that were previously protected by cooler climates. For example, prior to the COVID-19 outbreak, Pakistan reported that its hospitals were overrun with an outbreak of Dengue fever. Dengue can develop into an Ebola-like hemorrhagic fever.  The Aedes mosquito also carries viral diseases such as yellow fever, Zika, West Nile and many other life-threatening diseases with no cure.

This year, Africa, the Middle East and South Asia are facing a food crisis due to an outbreak of another sort: desert locusts. This locust is a voracious crop pest that can travel in a swarm up to 150 kilometers eating everything in its path. During plagues, swarms can cover an enormous area of 29 million square kilometers into up to 60 countries. This is more than 20 percent of the world’s total land surface. Outbreaks can damage the livelihood of up to 10 percent of the world’s population. An estimated 42 million people are acutely food insecure due to this year’s outbreak, which has been largely overshadowed by the COVID-19 pandemic. Pesticides are critical tools for controlling locusts worldwide, thereby increasing food security.

These concerns may seem far-flung, but closer to home there is a serious need for pest control as recent outbreaks of insect-borne diseases have emerged in the United States. Pests like fleas and lice carry bacterial diseases like typhus and trench fever. These illnesses were common in the Middle Ages and have had a recent resurgence. Concerning news reports from Los Angeles and Denver describe outbreaks of both diseases, which often require hospitalization and long courses of antibiotics. The plague, which killed a third of the European population in the 1300s, is also carried by fleas and endemic to the southwestern U.S.

Contrary to the unscientific and sensationalized claims in the press, pesticides – like vaccines, antibiotics and water sanitation – are vital tools that have afforded us an improved quality of life, food security and an unprecedented increase in life expectancy.

Pesticide Testing and Safety

The public has become concerned about pesticides because of sensationalized reports in the media claiming that there are health risks associated with exposure to them. Fortunately, regulatory agencies around the world have strict requirements governing safety. Companies are required by law to conduct a battery of toxicology tests prior to introducing a chemical on the market. That’s why the development of a new pesticide takes an average of 10 years and costs close to $250 million.

Pesticide studies are designed by regulatory agencies and regularly audited. Any adverse effects are reported by the companies to the agencies. These studies are conducted under the umbrella of “Good Laboratory Practice” which means that every test is validated and reproducible. The studies evaluate everything from environmental to human and animal health impacts of exposure and are critical for establishing exposure limits that are orders of magnitude lower than any level associated with toxicity. Moreover, regulatory agencies strictly enforce pesticide residue limits (also known as “tolerances”) on crops through schemes like the U.S. Pesticide Data Program. These limits are thousands of times lower than any level associated with toxicity, so by definition, pesticide residues are non-toxic. These exposures have no associated health risks and more importantly, use of pesticides on crops confer important benefits!

While this may seem confusing to people, it is important to understand that pesticides protect crops from insect-borne illness and toxic weeds. For example, when insects eat crops, they often carry fungal spores on their coats. These fungi can cause infections and often release potent human carcinogens such as aflatoxins. In order to prevent this kind of contamination, insecticides and fungicides are used. Herbicides are used to prevent crops from being contaminated with toxic weeds. In fact, last year there was a large recall of French green beans because they were contaminated with Datura stramonium. When people consume this plant, they develop an agitated delirium with vivid hallucinations and can die of heat-stroke. Therefore, it is critical to make sure these weeds do not contaminate the food supply.

In conclusion, for agriculture, pesticides are akin to medications for crops, preventing insect-borne illnesses and treating weed infestations that can negatively affect consumers. From a public health perspective, pesticides prevent the rampant epidemics of the Middle Ages, such as the plague and typhus. Contrary to the unscientific and sensationalized claims in the press, pesticides – like vaccines, antibiotics and water sanitation – are vital tools that have afforded us an improved quality of life, food security and an unprecedented increase in life expectancy. Ultimately, pesticides are critical for public health.

Eliza Dunn(Halcomb), MD, FACMT, is medical affairs lead at Bayer U.S. Crop Science in Chesterfield, Missouri, USA.

 

 

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