Houston’s ‘mosquito apocalypse’ reveals low climate impact preparedness
After Hurricane Beryl stormed through southeast Texas, locals began to notice a horrifying surge in the mosquito population, with some calling it “the mosquito apocalypse”. In the first ten days after the storm, residents of Harris, Fort Bend, and other counties found themselves, confronted with “walls” and “clouds” of mosquitoes upon stepping outdoors. Annoying as that is, the real problem is that mosquitoes carry diseases like West Nile virus, Dengue fever, and Zika.
All of these have been detected in the region. West Nile virus, in particular, has been found in mosquitoes that are part of this Beryl-induced surge. The Texas Department of State Health Services provides information about mosquito-borne diseases.
On July 29, Fort Bend County issued a press release announcing some areas would be subject to aerial spraying of insecticides — including residential areas — starting the next day. Aerial spraying would be done with an insecticide called Dibrom, which is a brand name for the chemical naled.
- The EPA-approved technical label for Dibrom notes the insecticide is restricted for use in the United States, “due to eye and skin corrosivity hazard”.
- The label also specifies Dibrom can be used “only by federal, state, tribal, or local government officials responsible for public health or vector control” or certified professionals in the appropriate category.
- Dibrom is “not for use in and around the home”.
- Earth Justice reports: “Even at low levels of exposure, naled can lead to serious negative health effects.”
The Fort Bend County press release directed residents to a Texas state website, which was posted after Hurricane Harvey, which offers answers to Questions about Aerial Mosquito Control. When reading through the list of points under the question about risks to humans and pets, it is clear that there are known and potential serious risks to health and wellbeing, and that people should have information about those risks and how to reduce or respond to them.
Numerous other public health websites say Dibrom/naled “breaks down quickly” or “degrades quickly” on contact with sunlight or water. What those public health authorities tend not to mention is that Dibrom breaks down into a carcinogenic neurotoxin called dichlorvos (or DDVP), which is restricted in the United States and banned in countries ranging from Bangladesh to Denmark.
According to a study published in Interdisciplinary Toxicology, in 2018, and reposted to the NIH Library of Medicine website:
“Acute and prolonged exposure may lead to death, genotoxic, neurological, reproductive, carcinogenic, immunological, hepatic, renal, respiratory, metabolic, dermal and other systemic effects. Its toxicity is due to the ability of the compound to inhibit acetyl cholinesterase at cholinergic junction of the nervous system.”
The same study cites other research that found that dichlorvos remains chemically intact in solution (in water), and therefore potentially harmful to human health, for a period of weeks to months:
“in winter temperature, dichlorvos was still present in filtered water (pH 6.1) after 180 days; residues in river water (pH 7.3) and filtered river water (pH 7.3) disappeared after 81 days; residues in sea water (pH 8.1) disappeared after 34 days. In summer, dichlorvos residues disappeared after 81, 55, 34 and 180 days for filtered water, river water, filtered river water and sea water, respectively.”
West Nile virus poses a serious threat to public health. It is not, however, news that climate change driven by global heating will lead to the spread of disease-carrying mosquitoes into new areas. Since the greenhouse effect was first understood in the 1800s, it was clear that one effect of a warmer climate would be changes in the distribution of ecosystems and species, including pests.
The mosquito apocalypse induced by Hurricane Beryl is a ripple effect of global heating, just as Beryl itself was. That the quick fix solution to a potential surge in disease carrying mosquitoes is to fly planes over residential neighborhoods to spread a toxic pesticide that breaks down into another, longer-lived toxic pesticide, is a sign of low preparedness for this kind of hazard.
This is another case of a part of the world that has for a long time made its living by investing taxpayers’ money in the fortunes of oil and gas producing companies finding itself threatened by climate-related risks to health and safety. Others include:
- devastating fires affecting the heart of Alberta’s tar sands operation,
- torrential rains and flooding affecting the United Arab Emirates,
- Iran experiencing heat index temperatures in excess of 150ºF,
- Saudi Arabia facing catastrophic fresh water scarcity,
- destabilizing desertification affecting Nigeria and surrounding countries,
- and of course, Hurricane Katrina devastating coastal Louisiana.
There are many more examples.
There are non-chemical methods of household mosquito control, which can also apply to areas where people gather, around restaurants, museums, parks, and shopping centers. For public health authorities, the concern is that they want to not just displace mosquitoes that might carry disease, but kill them. Comprehensive mosquito mitigation needs to be a long-term commitment, with careful planning and engineering of the local environment to reduce the incidence of disease-carrying pests.
This can include careful regulation and inspection of standing water and other structural decisions related to mosquito prevalence, as well as operational assistance to various kinds of facilities, including local water authorities, warehouses and manufacturing facilities, and yes, oil and gas operations as are found throughout the greater Houston area. This can also include municipal and private recreational facilities and commercial centers.
Urban planning and structural engineering should be part of the overall mosquito risk mitigation strategy in all regions, as global heating has driven an explosion of mosquito populations even in the subarctic and near Arctic regions.
Given the potential health risks posed by residual dichlorvos after aerial spraying with Dibrom, public health authorities should do more to support public awareness and responsible remediation actions. This can start with a clear public statement about known chemical residues from spraying, replacing previous statements of “quick” disappearance and “no risk”. It should also include responsible public health guidance on household and local remediation to remove any dichlorvos residue that might remain.
