UPDATE: West Nile Virus vs. Pyrethroid Exposure

You can read Wellness and Equality‘s original post last week about Dallas’ efforts to combat West Nile Virus here: “Pros & Cons: West Nile Virus vs. Pyrethroid Exposure”

What’s really in the air in Dallas?

Public anxiety over the aerial spraying of insecticide in Dallas to control mosquitos has raised questions about safety, but few concrete answers.  Instead of taking the manufacturer’s word that Duet Dual-Action Adulticide is safe, the public should be provided independent studies about the contents of the product itself.  Clarke Mosquito Control, the manufacturer, has a financial incentive to stand behind their polished marketing materials and safety assurances, but what’s really behind the green label?

The insecticide is a cocktail of three active ingredients: sumithrin, prallethrin, and piperonyl butoxide.

  •  Piperonyl butoxide is listed third on the Duet Dual-Action Adulticide label, but it may be the most harmful.

What are its common uses?  Piperonyl butoxide (PBO) is not actually an insecticide itself — instead, it increases the potency of the two other chemicals.  What this means is that although the label may show “safe” levels of other chemicals, the potency of those chemicals is actually much, much stronger in practice.

How does it work? PBO is a synergist which increases the toxicity of other chemicals: the more piperonyl butoxide in a product, the more powerful the other chemicals. The presence of piperonyl butoxide makes determining true levels of the other chemicals a murkier process.  Some products contain up to ten times more PBO than insecticides themselves. Of course, manufacturers often downplay the inclusion of PBO.

Is it safe?  Piperonyl butoxide is especially harmful to the developing fetal brain. A 2011 study, conducted at Columbia University and published in the journal Pediatrics, found that infants whose mothers had been exposed to low levels of piperonyl butoxide (PBO) during their third trimester showed delayed mental development by the age of three.  You can read the full study here, or a summary here.  A more recent study by Duke University study confirmed these findings and found that the chemical also interferes with signaling in the human brain. The Duke study, which was published in the journal Toxicological Sciences, found that PBO’s disruption of the critical neurological pathway “may be the molecular basis for profound developmental defects in children exposed in utero to PBO.”

  • Sumithrin: Sumithrin, also called phenothrin, is a synthetic pyrethroid.
  • Prallethrin: Prallethrin is also a synthetic pyrethroid.

What are their common uses?  Sumethrin and prallethrin are commonly used as insecticides to kill household insects, including mosquitoes.  They appear in products such as Raid, Enforcer, Ortho, and Anvil.  One of the most common uses of sumithrin is in flea and tick products for pets.  It’s also an ingredient in head lice products for humans.

How do they work?  As pyrethroids, sumethrin and prallethrin cause nerve paralysis in the insect, effectively shutting down the insect’s functioning.

Are they safe?  Sumethrin is a known endocrine disruptor, neurotoxin, and likely carcinogen. In 2005, the Environmental Protection Agency (EPA) revoked permission to use sumethrin in flea and tick products after thousands of cats and kittens were poisoned and killed by its use.  Few long-term studies on the safety of pyrethroid insecticides exist because they have only been in widespread use since after 2000 when the the EPA phased out the use of chlorpyrifos and other organophosphorus insecticides due to risks to child neurodevelopment.  Out with the bad, in the worse?

Dallas is not alone.  Almost all cities across the United States use insecticides to control mosquitoes and other summertime insects.  The New York Department of Public Health and Mental Hygiene advises the public — especially anyone with asthma or respiratory sensitivity — to remain indoors during spraying, close vents and turn off fans and air conditioners to reduce indoor exposure, remove children’s toys and outdoor furniture from outside and/or wash them before using again, wash all produce, and wash skin and hair if exposed to the pesticide.  These are fine recommendations, but my concern is that most people are unaware of the spraying schedules in their cities.

Do you know if and when your city sprays these toxic chemicals?

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Pros & Cons: West Nile Virus vs. Pyrethroid Exposure

In Dallas, Texas, it’s raining synthetic pyrethroid Duet Dual-Action Adulticide — 2,000 gallons of it, according to some estimates.  To contain the mosquito-transmitted West Nile Virus, airplanes will wash at least twelve cities in Texas with the toxic insecticide.

If you think this issue only affects Texans, think again.  In parts of California and Florida, aerial spraying of toxic insecticides has been a routine response to summertime mosquitos. Whether to respond to cases of West Nile Virus with aerial spraying will soon be a question faced by other areas of the United States as well. This week, an increasing number of West Nile Virus cases were recorded in Chicago and its surrounding suburbs.

As of this past Tuesday, the Centers for Disease Control and Prevention recorded 693 cases of West Nile virus in 32 states. 336 of those cases were reported in Texas. In all likelihood, many more unreported, symptom-free cases exist.

The Environmental Protection Agency acknowledges that, even when applied according to the label, synthetic pyrethroids pose “slight risks of acute toxicity to humans” and at higher doses “affect the [human] nervous system.” Some Dallas area doctors are advising patients with asthma or respiratory sensitivity to leave areas that are being sprayed.

Do officials really believe the aerial spraying is safe?  After all, many officials live within the limits of the regions that will be sprayed.  The answer, it seems, is that aerial spraying is safe for the public — but not safe for government officials.  According to several news sources, pilots were asked to avoid spraying former President George W. Bush’s home with the toxic insecticide.

Which is worse?  Exposure to West Nile Virus or exposure to Duet Dual-Action Adulticide?

West Nile Virus Facts:

  • 80% of those who contract West Nile Virus experience no symptoms and clear the virus without treatment.
  • 20% of those who contract the virus will experience flu-like symptoms (fever, body aches, swollen lymph glands).
  • If infected, you have a less than 1% chance of dying from the disease.
  • 1 in 150 people will have a severe reaction to the virus which could result in permanent damage or death.
  • Humans do not generally transmit the virus to one another, and are considered “dead-end” hosts.  (The virus can, however, be transmitted through blood transfusions, organ transplants, and breastfeeding.)

For comparison, what are the chances of experiencing side effects from pyrethroids? The truth is, we don’t know for sure.  When it comes to approving the use of chemicals, the Environmental Protection Agency behaves much like our judicial system: Chemicals are considered innocent until proven guilty beyond a reasonable doubt — and by that time, it’s often too late for those exposed.

Synthetic Pyrethroids (Insecticide) Facts:

  • Pyrethroids are used as insecticides because they kill insects, fish, and other invertebrates by interfering with, and rapidly shutting down, basic nerve cell functioning.
  • The EPA has classified pyrethroids as “likely to be carcinogenic to humans” if swallowed, inhaled, or otherwise ingested via the mouth.
  • Pyrethroids are a known endocrine disruptor.  Their estrogenizing effects include lowered sperm count in men, and the development of abnormal and cancerous breast tissue in both male and females.
  • Pyrethroids are a known neurotoxin.  Symptomos of neurotoxicity from pyrethroids in humans include nausea, headaches, tremors, seizures, lack of coordination, and elevated body temperature.
  • Pyrethroids are significantly more damaging to the developing systems of children than to adults.
  • Pyrethroids are significantly more harmful to cats than to dogs. (This is one reason manufacturers must make separate flea control products for canines and felines — cats’ livers are unable to handle the higher doses that dogs are able to survive.  Always explore non-toxic flea control for your pet before resorting to chemical products.)  UPDATE 8/19: View the Pet Poison Helpline’s list of pyrethroid toxicity symptoms in cats and dogs by clicking here.

Pregnant women, as is almost always the case, are most at risk to both disease and to chemical exposure since developing fetuses are more sensitive to toxins of any kind.  (On a side note, did you know that babies born in late summer and fall are more likely to develop asthma?  This outcome is generally attributed to pollen season cycles; however, in light of the knowledge that aerial insecticide spraying is most common during the summer months, could there be a link to third trimester insecticide exposure?)

So what can you do?  Unfortunately, there is little you can do to avoid pyrethroid exposure once your city has made the decision to approve aerial spraying without avoiding the area altogether, but there are natural ways to limit the mosquitoes around your home.

Here are some green mosquito control solutions:

  • Inspect the outdoor areas around your home and remove standing water (bird baths, puddles, etc.) since stagnant water sources are breeding grounds for mosquitoes.
  • If you plan to be outside, cover up – wear long pants and long sleeves.
  • Avoid applying scented lotions and perfumes to your body, which can attract insects to you.
  • Consider introducing natural mosquito predators to your backyard, such as mosquito fish or species of fungus. (To learn more about this method, look up “biological pest control.”)

Do you have any other green suggestions?  Please leave a comment below.

UPDATE 8/19: The rain in Dallas has slowed, though not halted, the aerial application of Duet Dual-Action Adulticide.  Given the response to this post, I wanted to provide two additional resources. To view the Pet Poison Helpline’s list of pyrethroid toxicity symptoms in cats and dogs, click here.  To read a sample label of Duet Dual-Action Adulticide, click here.  According to this label, the insecticide’s active ingredients are sumithrin, prallethrin, and piperonyl butoxide.

Read our updated analysis of Duet Dual-Action Adulticidie’s safety by clicking HERE. 

Image below shows geographical West Nile Virus infection. Via.