The impacts of mosquito spraying

A program of spraying is intended to quell the mosquito population, provide relief from those biting buggers, and hopefully prevent cases of West Nile disease around the Valley.

However, the Platte Valley is a natural ecosystem where every creature fulfills a role, and trying to manipulate that ecosystem can have negative consequences, right?

Maybe not.

And what about health hazards to humans? The answer seems to be that there is no need to worry. The greatest exposure to the insecticides seems to come from household items and simple measures can be used to prevent harmful doses.

According to a 2010 article in the peer-reviewed journal “Nature”, eliminating mosquitoes from the world may only be of benefit to humans and may have little lasting consequence to other species such as birds, bats, frogs, fish, spiders and flowers. In her article, Janet Fang said “With many options on the menu, it seems that most insect-eaters would not go hungry in a mosquito-free world. There is not enough evidence of ecosystem disruption here to give the eradicators pause for thought.”

There are no known species of plant or animal which feeds solely on mosquitoes, and studies have shown while there may be an initial decline in some populations after the removal of mosquitoes, the gap in the diet would be replaced eventually.

From a human perspective Daniel Strickman, the Program Leader for Medical and Urban Entomology at the US Department of Agriculture says “The ecological effect of eliminating harmful mosquitoes is that you have more people. That’s the consequence.”What about the unintended consequence of killing other insects or even reptilian or avian species with the use of insecticides? The town of Saratoga has contracted the use of both larvicides, chemicals designed to kill mosquito larvae, and adulticides to kill mosquitoes in their flying form.

The chemicals being used are the larvicide VectoBac 12as and the adulticide Biomist 3+15 ULV.

The active ingredient in VectoBac is Bacillus thuringiensis var. israelensis (Bti), a bacteria which is a naturally occurring in certain soils. Bti is only toxic to insects that have specific receptor sites in their stomachs and is only known to kill certain primitive flies, particularly mosquitoes, black flies, and some midges. Bti has been shown to reduce populations of stone flies and May flies after three or more years of use, but this does not seem to have affected the overall number of insects or birds and reptiles in an area.

The active ingredient in Biomist is permethrin, a synthetic pyrethroid. According to the US Fish and Wildlife, there have been very few studies on the non-target effects of adulticides like permethrin, but preliminary evidence suggests some fish species and aquatic invertebrates may be harmed by the insecticide.

Permethrin has been shown to be extremely toxic to bees if they come into contact with the chemical during spraying or up to a day later. This can affect the pollination of plants in sprayed area. The jury is still out, but if applied properly to kill mosquitoes the damage to the environment from the use of permethrin seems to be minimal.

Chuck Bartlett, engineer for the town of Saratoga, said the town used to use Scourge insecticide, but has used the less harmful Biomist for at least the last three years. The larvicides and adulticides are applied by a mixture of aerial spring with planes, truck mounted foggers, and weed sprayers in areas with small ponds or other bodies of standing water.

Based on the available data, the insecticides being used seem to be the safest available, but there have not been any long term studies on the larger effects of these chemicals. It may be up to the community of birders, entomologists and anglers to determine the effects on the local environment.

In a report on the toxicology of pyrethrins and pyrethroids written for the U.S. Department of Health and Human Services the dangers of the pesticide seem to be extremely limited. The report shows that the chemicals breakdown quickly in the natural environment lasting only up to two weeks after application.

Furthermore, since the pyretheriods bond to soils they do not leach into groundwater and have not been seen in high levels in drinking water except in areas near toxic waste sites.

The most common ways for humans to ingest permethrin are through inhalation and absorption through the skin. Most exposure comes through the use of insecticide sprays, aerosol bombs, pet shampoos, and lice treatments.

Exposure has also been shown to occur after eating fruits, vegetables, and grains sprayed with insecticides.

Even with the use of these products and foods, according to the study, the average daily intake of permethrin in U.S. for a 154-pound adult is 1,000 times less than the acceptable level before harmful effects occur as determined by the United Nations Food and Agriculture Organization and the World Health Organization.

Signs of toxic levels of permethrin include tremors, writhing, and salivation. The chemical most notably affects the nervous system and if symptoms occur medical help should be sought immediately.

Various studies have found no link between permethin and statistically significant increases, in either adults or children, in cancer, developmental effects, or reproductive effects.

Children can be more susceptible to infestation of permethrin because they tend to have more contact with soil and dirt. Although, no noticeable harmful effects to children from conception the age of 18 have been shown in any studies.

Preventative measures for avoiding ingestion of insecticides include keeping your windows closed during spraying or fogging, turning off air conditioners and swamp coolers, using household insecticides and pet shampoos according to the manufacturer’s instructions, and washing areas that come in to contact with household pesticides.

In short, don’t follow the fogger around on your bike and stay inside if the aerial spraying plane is passing over your house.