In the wake of Hurricane Matthew — to spray or not to spray?
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Confronted by devastating Hurricane Matthew, Florida residents and city officials have even more to deal with than the obvious destruction and loss at hand. 

When floods and rain subside, stagnant puddles and newly formed ponds persist — a perfect breeding ground for mosquitoes. What this has meant previously is aerial spraying of highly toxic organophosphate pesticides (OPs).

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Just recall Hurricane Isabel in 2003, or Charley, Jeanne, Frances, and Katrina in 2004 and 2005. Don’t forget Hurricane Irene in 2011. In all instances, flooding resulted in real or anticipated increases in mosquito abundance, and aerial spraying of toxic OPs ensued.

Out went the hurricanes and in came the pesticides. Will this be the story again following hurricane Matthew? It’s only been weeks since Miami Beach experienced repeated aerial spraying of the insecticide Naled in spite of much protest by locals. Yet history would suggest Florida may be in for another spray.

Naled is a potent neurotoxin being used to kill mosquitoes in order to combat the spread of Zika virus. It is also a chemical the European Union banned in 2012. Meanwhile in the U.S. Naled remains the weapon of choice come virus or natural disaster, with nearly 6 million acres of land sprayed in Florida in 2014 alone. As a public health scientist specialized in chemical exposure assessment, I provide a word of caution against this frequent aerial OP spraying.

OPs affect cholinesterase inhibition in the body, and is toxic to the nervous system. While they have been widely used since WWII, their use has not been without consequence.

Rather, a number of scientific studies have shown an association between OP exposure and neurological outcomes such as attention-deficit/hyperactivity disorder, or ADHD, and neuro-developmental impacts to the unborn fetus. Studies have also shown pre-natal OP exposure linked to premature birth, reduced birth weight, and cardiovascular abnormalities. One study showed childhood exposure linked with reduced lung function. OPs can cause toxicity through all routes — inhalation, consumption, and physical skin contact.

According to the Centers for Disease Control and Prevention (CDC), aerial spraying of Naled is inconsequential to human health because the quantities used are very low. This assertion, however, neglects that low dose exposure, particularly repeated exposure, can be problematic if you’re someone prone to chemical intolerance.

As we say, “dose plus host” determines toxicity. This is because people’s ability to detoxify OPs and other chemicals varies greatly from person to person. For some, exposure may go unnoticed. For others, the consequence can be severe and long lasting. Unfortunately, there is no easy way to know which child or adult is genetically susceptible—until it’s too late. That is, until they’ve been exposed. 

Chemical intolerance afflicts many people and can be triggered by repeated low level OP exposure. Dr. Claudia Miller, a physician and research scientist with three decades of experience studying the health effects of OPs and other chemicals, has investigated numerous exposed populations and established a strong link between OP and other low level exposures and chronic health problems. She coined the term Toxicant Induced Loss of Tolerance, or TILT, to describe the two-stage physiological process of an initial chemical exposure followed by subsequent intolerances to many other chemicals.

People who get “TILTed” lose their capacity to tolerate common, chemically unrelated substances such as fragrances, cleaning products, nail polish, and vehicle exhaust. Once TILTed by an initial chemical exposure, these substances can trigger serious health problems such as fatigue, headache, weakness, mood changes, difficulties with memory and concentration, as well as respiratory and skin problems. Symptoms from even a single exposure leave some people debilitated for life. 

In the last decade TILT has become increasingly well documented and studied worldwide by doctors and medical researchers. A validated questionnaire called the Quick Environmental Exposure and Sensitivity Inventory (QEESI) has been developed to help patients and doctors identify this elusive disease process. The QEESI is now being used in more than a dozen countries.

Of great concern in Florida and elsewhere are the repeated OP exposures among susceptible individuals in the spray zones. They and their doctors must be aware of the two stages of TILT, which can develop in the days and weeks following a salient exposure event, such as the recent sprayings in Florida and potentially another in the wake of Hurricane Matthew. Early diagnosis and avoidance of symptom triggers is essential to getting well — similar to when someone develops an allergy to a food or drug.

However, TILT differs from usual allergies in that the specific antibodies that characterize allergic sensitization are largely absent. Consequently most diagnoses are missed by doctors and allergists. Nor are there accepted lab tests for TILT. The QEESI questionnaire is currently the most reliable tool for screening.

Disaster relief efforts are undoubtedly of utmost importance following devastating hurricanes. The routine accompaniment of aerial OP spraying to such efforts, however, must be questioned and suggests the impacts of low level OP exposure are underappreciated. Naled, like many OPs, affects more than just mosquitoes—with every man, woman, and child in the spray zone at risk of developing TILT. And let’s not forget the prenatal impacts during pregnancy.
 
Without question, Zika represents a public health threat that necessitates urgent action. Indeed this will complicate the post-Matthew response efforts. We can be sure, however, that resorting again to aerial spraying of highly toxic OPs is simply opting for one of two evils — replacing mosquitoes with yet another problem. Given our current inability to identify OP-susceptible individuals, spraying cannot be carried out with necessary prudence.
 
As a precautionary measure, residents should therefore be made aware of the risks and be encouraged to remain inside with closed windows during aerial spraying; something the CDC currently deems “not necessary” on its website. Meanwhile, alternative vector control strategies by CDC and other agencies should be thoroughly investigated and funded accordingly by Congress. Aerial OP spraying should be an infrequent resort, if ever a resort at all.

Shahir Masri is an assistant specialist in air pollution exposure assessment and epidemiology. He has his Doctor of Science degree from the Department of Environmental Health at the Harvard T.H. Chan School of Public Health.


 

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