When the county knows best--or does it?                                December 2004

West Nile virus, an illness transmitted from wildlife to humans by mosquitoes, has made its second appearance in two years in Phoenix, Arizona, resulting in a number of confirmed fatal cases among birds and a growing number of positive cases in humans, reported by hospitals and doctors to the Maricopa county health department's vector control program. In response, the county has tracked the locations of most intense activity, has ramped up its public education program to ask people to be vigilant in draining any stagnant water sources where mosquitoes breed, and advised the public to wear repellent, particularly in the evenings, at night, and early morning when the insects are most active.

After plotting the outbreaks, the county identified a large 'hot zone' of cases and determined that this area -- mostly residential neighborhoods -- should be fogged with insecticide to reduce the mosquito population. The insecticide of choice is a synthetic pyrethroid called Anvil. According to the EPA "pyrethroids can be used ... without posing unreasonable risks to human health when applied according to the label. Pyrethroids are considered to pose slight risks of acute toxicity to humans, but at high doses, pyrethroids can affect the nervous system." *

Maricopa county proceeded with a program to fog an area of about eight square miles in the early morning hours of a Friday; a time when mosquitoes are active, winds are calm, and most people are in their homes asleep. Maricopa county also made the decision to not notify  residents in the affected area in advance that their neighborhood would be fogged.

Many of those homes, however, use evaporative cooling, a process that draws outdoor air into the home. The pesticide fog was also drawn into the homes, and the residents exposed while they slept. Some symptoms of pyrethroid exposure include rash and breathing difficulties. Persons with lung ailments and small children are susceptible at a lower dosage than the 'average' person. Persistent exposure or exposure to large concentrations can cause other health problems. Pyrethroids are a carcinogen.

While it is unknown how many residents of Phoenix were affected by the insecticide, none knew they may have been exposed. Therefore none knew whether, if they did show symptoms, they should seek medical treatment. I am one who came down with a rash after sleeping with an evaporative cooler running on a night when the county fogged my neighborhood.  Evaporative coolers bring in outside air, cooling the air with water.  In this case, the water was off, so it was ambient outdoor air being drawn in. I woke up to the smell of it, but had no idea as to the source.  I learned a few days later that one of my neighbors saw the trucks on our street at 3 a.m.  the day I came down with the rash.

The ethics question -- aside from any legal exposure notification or informed consent requirements -- is: "why did the county health department proceed with this application of pesticides without notifying the residents in the target area that they could be exposed, what the pesticide was, and what actions they should take if they wished to limit their exposure?" Is it possible that county officials believed they knew what was in the best interest of the citizens? Or was this just an act of insensitivity or incompetency?

*http://www.epa.gov/pesticides/factsheets/pyrethroids4mosquitos.htm

Submitted by Thomas Babcock
tom.babcock@phoenix.gov