Distribution of pesticide residues within homes in central New York State

Residues for 17 pesticides were analyzed in 41 households in central New York State that represented farm, rural, and urban houses. Samples were taken in both summer and winter of 2000-2001 from the same households from four locations; family room carpet; adjacent smooth floor; flat tabletop surface; and settled dust collected in a Petri dish on a tabletop. Pesticide residues were analyzed to identity factors that influence both the transport into and the redistribution of pesticides in the indoor environment. Differences were observed between the various pesticides and pesticide classifications relative to location within and between households as well as by season. Variations in the pesticide residues were related to a number of factors. Higher residues were observed in the farm households, particularly in summer, with the highest amount observed for chloropyrifos in carpet (33 microg/m2). For many pesticides, the frequency of detection and the amount of residues were higher in summer, which relates to usage patterns in agriculture and horticulture; however, larger amounts of insecticides such as mecoprop, resmethrin, and tetramethrin were found on flat surfaces in winter, indicating household use and possible redistribution within the home. Distribution patterns suggest that routines within a household may cause high variation in residues; these practices include indoor pets and treatment for fleas and ticks, use of termiticides, and fastidiousness of occupants. Frequency of pesticide detection was highest in carpet for both summer and winter for all households, indicating that carpets hold pesticides over time. Adsorbent fibrous materials such as textiles hold pesticides by macro- and micro-occlusion in their complex structures. Amounts of pesticide residue were higher in carpets than on smooth floors, particularly for rural farm households where the farmer was a certified pesticide applicator. The maximum amount of pesticide residue on a smooth floor surface was 13.6 microg/m2 malathion while the maxima on wiped surfaces and in settled dust were 1.8 microg/m2 2, 4 D and 3 microg/m2 pendimethalin, respectively. Physical properties of individual pesticides such as vapor pressure influenced the distribution of the pesticide within the households. Evidence of volatilization of pesticides and redeposition on surfaces was observed, indicating that this is a mechanism for contamination of surfaces in addition to adsorption on airborne particles and tracking. High residues in winter are evidence that closure of households in winter that reduces ventilation results in redistribution of pesticides within households.