Hill Valley Home Owners Association

 I can confirm to you that a complaint on Mellowood Drive did bring us to your neighborhood.
    We determine the areas where we will spray on the same day we spray them in order to respond to immediate need.   We operate over 60 monitors around the county where we capture, catalog and record the quantities and species of mosquitoes present.  This also includes a type of monitor which captures mosquitoes specifically suited to West Nile testing.  Unfortunately, mosquitoes are populations are highly variable around the county and we could never have enough man power to operate enough to cover the entire city at once.  Many species of mosquitoes will go their whole lives without ever moving more than a few city blocks from where they originated.  Indianapolis is 368 square miles, so even having one monitor per square mile would be prohibitive in terms of labor.  Therefore, we also rely upon the public to inform us when mosquito populations are high in their area.
    This is the reason why we sprayed your neighborhood last night and the only reason we will ever spray it.  If we do not have information from either a trap deployed in your area or a resident telling us that they are experiencing above average mosquito activity, we do not spray.   I think we can both agree that spraying if there is no need would be wasteful.
    Our program is primarily focused on larviciding.  Mosquitoes are easier to target in their aquatic larval and pupal stages and the means we can use to target them in those stages is decidedly non-toxic.  We can use a thin layer of oil (we have in the past used products based on soy oil and coconut oil) to essentially smother them (mosquito larvae are aquatic but need to come to the surface for air) or, in the case of containers or tires, simply removing the breeding habitat entirely.   We also provide fish to people with horse troughs, ornamental ponds, abandoned swimming pools or unscreened rain barrels.  As they are generally hardy enough to multiply and survive the winter in those sorts of containers, that is often a permanent solution.
    However adult mosquitoes are more vexing.  We have purple martin houses strategically located at the Belmont sewage treatment plant and other key sites, but generally speaking the only realistic way to target them is with pesticides.    Per EPA regulations, all pesticides sold in the United States categorized by one of three “keywords” on the label.   Either caution, warning or danger.   Items labeled danger are toxic and must be handled carefully.  Those labeled “caution” are of the lowest concern.  We only use products with the “caution” keyword.
    Specifically, we use a product called Anvil 2+2.  The active ingredient is sumithrin.  It does contain a warning that it can be toxic to fish, however this warning only applies if the product is misused or spilled as the quantities required to harm fish are far in excess of the quantities used when the other restrictions on the label are adhered to.   Sumithrin is a pyrethroid—a class of chemicals created by slightly tweaking a natural pesticide produced by an orchid called pyrethrum.   Life caffeine, another natural pesticide, pyrethrum and pyrethroids work by exciting the nervous system and symptoms from overexposure are very similar to those of caffeine overdose (jitteriness, shortness of breath, heart palpitations, etc).  However, the actual levels of active ingredient required to cause those symptoms are far less than the amount of caffeine required to cause those symptoms and far, far below the minute quantities we use in our spraying (an amount that works out to be about 1/60th of an ounce per acre once you account for drift).
    Because most mammals have liver enzymes that allow them to very quickly metabolize small quantities of pyrethroids safely, exposures to the extremely small amounts we spray are not known, despite extensive testing required by the EPA, to pose any risk to human health whatsoever under normal circumstances.   
    Despite this, it is our policy that when our drivers spot people outside working or playing on their lawns or out walking, that they turn off their spray when they pass by.  We do this for three reasons:

1.    We don’t wish to trigger anyone’s asthma inadvertently.

2.    There are extremely rare cases of people being allergic to pyrethroids.

3.    We just don’t want to ruin anyone’s fun.

    When we do turn off the spray, the engine continues to run (and it’s quite noisy if you are outside).  Consequently, it might not always be obvious when the spray is off to the casual observer.    
    If you are concerned about residual exposure, you needn’t be.  Our fog is a mist of tiny droplets that drifts only about 300 feet before settling out.  It hopefully remains aloft for up to ten minutes, during which it’s toxic to insects which fly through it.  After which time it settles out in quantities so minute that its not even toxic to  insects anymore.   And, since pyrethroids have weak chemical bonds, the UV radiation they are exposed to when sun is back out will very quickly break down even those trace amounts.  The molecule for Sumithrin contains only hydrogen, carbon and oxygen atoms so that once broken down, there are no inherently toxic elements like mercury, arsenic, lead, etc. left in the environment.
    It id not a fair statement to suggest that are exposing the public to a “dangerous pesticide” both because “dangerous” is a vast overstatement and because exposure is extremely limited or nil.
    I would like to inform you that we do maintain a notification list for people who want to be aware that we will be in the area beforehand.   Due to the nature of our program, you would receive those calls on the same evening we go out to spray — generally, though not always, at least 3-4 hours in advance. The list is primarily for beekeepers and people who have medical conditions such as allergies or asthma which they believe warrant additional caution, however anyone who wants to be added can be added.

Thank you,

Ryan Mercado
Environmental Health Specialist
Marion County Health Department
Office: (317) 221-7452