The District, the Public Health Department and the Board of Supervisors have carefully weighed the risks and benefits of treatment. The Federal and California EPA, scientific literature, decades of ULV use across the country and treatment operations in Santa Clara County since 2005, all attest to the safety and effectiveness of ULV treatments.
The District uses truck-mounted treatment machines that travel down the street releasing a very fine mist of the treatment product. The District ensures that its equipment is delivering the proper droplet size by using a process called calibration, and the output of the truck-mounted treatment equipment is regulated by radar signals detecting the speed of the truck.
The products Vector Control currently uses in its treatment operations to kill adult mosquitos are called Zenivex® E4 and Merus™ 2.0 (see table below). Both are EPA approved for public health pesticide applications. The EPA provides strict instructions for the usage of Zenivex® and Merus™ and any deviation from these instructions violates federal law.
The County operates in compliance with these instructions, and also submits to inspection by the California Department of Health Services and the local Agricultural Commissioner’s Office. More information on the EPA’s evaluation of Zenivex® and Merus™ can be found here.
Ultra low volume (ULV) treatment for adult mosquitoes reduces the risk of human WNV infections when used as a part of an overall IPM program. If the County did not treat when infected mosquitoes are found, cases of West Nile Virus could become more prevalent in Santa Clara County and cause significant health problems for those who get a symptomatic infection. To get a sense of how significant these problems can be, have a look at this video.