A comment from Dr. Lawton

A few reader comments were generated by the VTDigger article about the imminent DEC decision on the BLSG Insect Control District’s permit to operate. The full verbatim text of a comment by Dr. Benjamin Lawton, the chair of the BLSG, follows with some comments.

Ben Lawton’s (B.L.) comment in italics, our response in blue.

B.L. I have some additions and corrections to the article on mosquito control first notices of intent to apply insecticides are posted at the town clerks offices in the local newspapers and through public service announcements and on our website :blsgmosquito.wordpress.com

Residents would like to be alerted whenever spraying happens on their road. This would allow them to take the actions recommended by the EPA if they are concerned about exposure to pesticides (e.g., for malathion: closing windows, bringing in children’s toys, covering gardens). Could the BLSG district send an email to a few people who can announce (e.g., via social media) that an action threshold has been reached and spraying will occur that evening?

B.L. Any citizen can opt out of adulticiding and their property boundaries will be posted as a no sprays zone !!!

The BLSG website states that pesticide spray from the truck can drift up to 150 feet from the truck. When someone opts out of spraying along their property, does the truck stop spraying 150 feet from that property and start again only when the truck is 150 feet past the property? If this does not happen, isn’t it true that a resident cannot really opt out of exposure to pesticides?

B.L. The district uses ultra low volume applications (the minimum affective volume of a pesticide) against the flying adult mosquitoes. Both ground and Ariel ULV Applications have been the standard method of mosquito adulticiding World wide for more than 45 years

( by the way, the mosquito is the most deadly organism known to man. !)

Technically, mosquitoes have not killed anybody. Several different arboviruses and other microorganisms carried by mosquitoes have killed many. Millions of people have contracted these diseases, most of which ( malaria, yellow fever, Chikungunya, dengue fever, filariasis, Zika virus) are not present in mosquitoes in Vermont.

B.L. The optimum size droplet for mosquito control with field applied ground ULV has been determined to be 5 to 25 µm which is optimal for truck Based sprayers!

This contradicts published studies. Optimum droplet size for effective (≥90% mortality) mosquito control by space spraying via ground application equipment is 8–15 μm (Mount 1998), while a slightly larger droplet size (5-25 μm VMD) is most effective when applied by aerial methods (Mount et al. 1996).

Mount, G. A. 1998. A critical review of ultralow-volume aerosols of insecticide applied with vehicle-mounted generators for adult mosquito control. J Am Mosq Control Assoc 14:305–334.

Mount, G. A., T. L. Biery and D. G. Haile. 1996. A review of ultralow-volume aerial sprays of insecticide for mosquito control. J Am Mosq Control Assoc. 12(4):601-18.

B.L. The ultimate goal is targeted applications with minimal nontarget exposure. Other flying insects do not appear to be affected by mosquitocidal sprays if their body mass is larger than that of a mosquito .

So a small nocturnal mayfly, caddisfly, beetle, or moth can fly through the white cloud sprayed by the truck and be unharmed? What published study suggests that non-mosquito insect species are not harmed by the spray? In those studies, how many species are harmed?

B.L. (Lawler etal 2008,Jensen etal 1999) Found non-detectable concentrations of Pyrethrins and permethrin In water samples from wetlands, before and after truck mounted ULV applications.

I have not been able to find the Lawler or Jensen articles cited above, but other work by these same authors demonstrate the severe effect of pyrethrin, malathion, or permethrin on small insects and other arthropods. For example:

“… significantly (P< 0.001) higher diversity and numbers of nontarget arthropods were found dead on tarps in the treatment sites versus the Davis and non-Davis control sites (Table 2). All of the dead nontarget species were small-bodied arthropods belonging to >25 families in the following orders: Blattodea, Coleoptera, Collembola, Diptera, Hemiptera, Hymenoptera, Psocoptera, Thysanoptera, Acari, and Araneae.”

The orders listed include beetles, springtails, flies, bugs, bees and wasps, thrips, mites, and spiders.

Source: Nontarget effects of the mosquito adulticide pyrethrin applied aerially during a West Nile virus outbreak in an urban California environment. Walter M. Boyce, Sharon P. Lawler, Jennifer M. Schultz, Shannon j. Mccauley, Lynn S. Kimsey, Michael K. Niemela, Carrie F. Nielsen, and William K. Reisen. Journal of the American Mosquito Control Association 2007 23 (3), 335-339

B.L. Results from risk assessments (Schleier etal2009 ,Peterson’s etal2006) and the current weight of scientific evidence indicates that human health risk from residential exposure to mosquito insecticide are low and not likely to exceed levels of concern!

What does it mean that “health risk” is not likely to “exceed levels of concern?” This suggests that there is some health risk, so the above statement is false if there is not much concern. Does that mean that many people in the BLSG district are concerned about pesticide spraying?

Both of the articles cited are modelling studies. Creating the models required that someone assign relative importance to exposure to pesticides and to contracting a disease. No actual data were collected on the consequences of spraying or the consequences of mosquitoes on actual humans.

One of the authors of Schleier et al. 2009 worked for ICM Ventures, Fort Collins, CO. which might have been a petrochemical-related company.

Schleier et al. 2009    

Peterson et al. 2006

B.L. Furthermore, the results indicate that, based on human health criteria, the risk from west Nile virus and equine encephalitis exceed the risks from exposure to mosquito insecticide!

It is not clear what “human health criteria” are, but this does not seem to say anything different from the last statement.

B.L.  In 2012 there were two deaths from EEE In the local towns transmitted by mosquitoes!!!!!

From 2007 to 2016, the average annual incidence of EEE in Rutland County was less than one case per 200,000 people. In Addison County, the 10-year average was zero. This seems like an exceedingly small risk of contracting the disease. In that 10 year period, 2012 was the year of highest incidence of EEE in the US, and it has been much lower since then.

Has anything changed in the operations of the BLSG Insect Control District since 2012 that suggests that those operations will now protect residents from mosquito-borne diseases?

This map shows the distribution of Eastern equine encephalitis virus neuroinvasive disease (encephalitis and/or meningitis) average annual incidence by county of residence from 2007 through 2016. Counties are shaded according to incidences ranging from less than 0.20, 0.20 to 0.49, and greater than 0.50 per 100,000 population. Shaded counties are primarily distributed along the Gulf Coast, Eastern seaboard, and the Great Lakes. Map source: https://www.cdc.gov/easternequineencephalitis/tech/epi.html

B.L. BLSG has been providing mosquito control since 1987 to the area town’s. Unfortunately many of the newer residents of the area have not experienced the clouds are mosquitoes that once infested the area prior to initiating control !!!!!

This is a very important result. The former Vermont State Entomologist, Alan Graham, counted adult mosquitoes in the BLSG district during 1989 and in most years since 2001. I assume that is the source of the information you are referring to. It would be good to see Alan Graham’s report on the long-term trend in mosquito population density in these towns. I am not aware of population data from earlier years so there might be no scientific evidence of your suggested longer term changes in mosquito density. If there is no verified trend in mosquito populations, then there is no basis for inferring any effect of insect control treatments on those populations. If adult mosquito populations have declined over the years because of control measures, this could be due to larvicide treatments which are not a source of concern for residents. Residents are concerned about malathion and permethrin being sprayed along town roads.


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