Following the Environmental Protection Agency’s phase-out agreements with the manufacturers of organophosphate insecticides chlorpyrifos and diazinon in 2000 and 2001, the Columbia University researchers sought to determine the impact of the new regulations on pest infestation levels, pesticide use, and pesticides measured in indoor air samples. They enrolled 511 pregnant women from inner-city New York between 2000 and 2006. Permethrin, a pyrethroid insecticide; PBO, a pyrethroid synergist; chlorpyrifos; and diazinon were measured in 48-hr prenatal personal air samples. Data on pest infestation and pesticide use were collected via questionnaire.

88% of women report using pesticides during pregnancy and 55% report using higher-exposure pesticide applications (spray cans, pest bombs and/or professional pesticide applicators). Self-reported pest sightings and use of higher-exposure applications increased significantly after the regulations were implemented. PBO, cis-, and trans-permethrin were detected in 75, 19, and 18% of personal air samples, respectively. Detection frequencies of PBO and cis- and trans-permethrin increased significantly during this time period. Levels and/or detection frequencies of these compounds are significantly higher among mothers reporting use of high exposure pesticide applications. Chlorpyrifos and diazinon levels decrease significantly during this time.

PBO, a highly toxic substance that causes a range of short- and long-term effects, including cancer and adverse impacts on liver function and the nervous system, is one of the most commonly used synergists in pesticide products. Synergists are chemicals added to pesticide formulations to enhance the toxicity of the active ingredients. PBO is frequently used, especially in aerosol products and mosquito sprays, to increase the potency of pyrethrin and synthetic pyrethroids, as well as other types of insecticides. Products generally contain between five to ten times as much PBO as pesticide product active ingredient. PBO has been associated with decreased liver function.

Permethrin is a possible human carcinogen and exposure is linked to possible endocrine disruption, immunotoxicity, neurotoxicity and reproductive effects. It is also highly toxic to fish, aquatic organisms, and bees.