Agricultural pesticide use in California: pesticide prioritization, use densities, and population distributions for a childhood cancer study.

Several studies have suggested an association between childhood cancer and pesticide exposure. California leads the nation in agricultural pesticide use. A mandatory reporting system for all agricultural pesticide use in the state provides information on the active ingredient, amount used, and location. We calculated pesticide use density to quantify agricultural pesticide use in California block groups for a childhood cancer study. Pesticides with similar toxicologic properties (probable carcinogens, possible carcinogens, genotoxic compounds, and developmental or reproductive toxicants) were grouped together for this analysis. To prioritize pesticides, we weighted pesticide use by the carcinogenic and exposure potential of each compound. The top-ranking individual pesticides were propargite, methyl bromide, and trifluralin. We used a geographic information system to calculate pesticide use density in pounds per square mile of total land area for all United States census-block groups in the state. Most block groups (77%) averaged less than 1 pound per square mile of use for 1991-1994 for pesticides classified as probable human carcinogens. However, at the high end of use density (> 90th percentile), there were 493 block groups with more than 569 pounds per square mile. Approximately 170,000 children under 15 years of age were living in these block groups in 1990. The distribution of agricultural pesticide use and number of potentially exposed children suggests that pesticide use density would be of value for a study of childhood cancer.

Pesticide exposures to children from California's Central Valley: results of a pilot study.

In response to concerns about pesticide use and evidence that contaminants may accumulate in house dust, the California Department of Health Services (DHS) conducted a pilot study of pesticide contamination in rural children's home environments. House dust samples for pesticide analysis were collected from eleven homes, five of which had at least one farmworker (FW) resident. Handwipe samples were collected from one child at each residence (ages 1-3 years). Ten of 33 pesticides tested in house dust were detected. Excluding non-detects, concentrations for diazinon ranged from 0.7-169 ppm in four FW homes and 0.2-2.5 ppm in three non-farmworker (NFW) homes (overall median = 1 ppm), suggesting a difference between FW and NFW homes. Chlorpyrifos ranged from 0.2-33 ppm in three FW homes and < 1 ppm in two NFW homes (overall median < 0.5 ppm). All other pesticides were detected at < 2 ppm at four or fewer homes. The sources of these compounds could not be determined. Co-located samples were considerably different in concentration and loading, indicating intra-household variation. Of nine compounds tested, diazinon and chlorpyrifos were found on the hands of two or three FW children (20-220 ng/hand). Dust ingestion scenarios show child exposures could exceed the United States Environmental Protection Agency Office of Pesticide Program diazinon chronic reference dose (9 x 10(5) mg/kg/day). The results suggested that pesticide residues are present in the home environment of some California children and are likely to contribute to exposures. Additional research is feasible and needed to assess the magnitude and distribution of these risks.

Malathion and malaoxon environmental levels used for exposure assessment and risk characterization of aerial applications to residential areas of southern California, 1989-1990.

Between August 1989 and July 1990, California conducted a Mediterranean fruit fly eradication project in southern California which included repeated aerial applications of malathion bait to urban areas where approximately 1.6 million people resided. Concern about the safety of these applications prompted the California Department of Health Services to prepare a risk assessment. The current work presents the estimates of environmental levels of malathion and malaoxon, derived from mass deposition rates during application and monitoring of air. We estimated short and long-term malathion and malaoxon levels on outdoor surfaces, plants, and soils (0.1 and 1.0 cm mixing depth), using a simple first-order exponential decay model and literature half-life values ranging from three to nine days. Direct monitoring data were used to characterize short-term air levels. Average and upper-bound malathion levels immediately following an application were 0.091 microgram/m3 and 0.207 microgram/m3 in air; 22 and 52 mg/m2 on outdoor surfaces; 3.8 and 9.6 micrograms/g in plants; and 1.5 and 3.5 micrograms/g in soil (1 cm mixing depth). Malaoxon levels were 0.039 microgram/m3 and 0.110 microgram/m3 in air; 0.15 and 0.46 mg/m2, 0.03 and 0.09 microgram/g, and 0.01 and 0.03 microgram/g, respectively. Estimates of average and upper-bound levels over the duration of the eradication program were roughly one-third the immediate levels in all media. No field measurements were available for co-products other than malaoxon, for environmental persistence, or for concentrations on surfaces, soil, or plants after repeated applications. Because of limited monitoring data, and the likelihood that similar pest-eradication programs will be conducted, additional studies are warranted to more accurately characterize the environmental fate of malathion and human exposures after aerial application to residential communities.

Assessment of exposure to malathion and malaoxon due to aerial application over urban areas of southern California.

The state of California conducted aerial applications of malathion (MA) bait over urban areas in the southern California air basin in order to eradicate the Mediterranean Fruit Fly (Ceratitis capitata). Concern about the potential human health effects of this activity prompted a risk assessment conducted by the California Department of Health Services. Estimates of potential human exposures to MA and its primary breakdown product, malaoxon, (MO) are based on assumptions of daily human activities which influence the rate of contact with MA and MO. Several exposure scenarios, representing a range of activity levels from sedentary to very active, are used as surrogates for a variety of human activities. For each exposure scenario, acute dose rates are calculated using both the mean and the mean plus 2 standard deviations (SD) (98% upper confidence limit (UCL)) of measured environmental values. Chronic dose rates are calculated using long-term averages incorporating degradation and multiple applications at 14 day intervals, and the estimated 98% UCL for these averages. Based on this model, estimated adult dermal doses (1-246 micrograms/kg-d) are up to about 2000-fold higher than the estimated inhalation doses (0.01-0.1 microgram/kg-d) but are comparable to the doses from ingestion of contaminated unwashed backyard vegetables (30-80 micrograms/kg-d). For the individual who does not consume backyard vegetables, therefore, almost the whole dose of MA or MO would be due to contacting contaminated surfaces with skin.

Temporal trends in the incidence of non-Hodgkin's lymphoma and selected malignancies in a population with a high incidence of acquired immunodeficiency syndrome (AIDS)

Annual incidence rates for 1975-1985 were derived for Kaposi's sarcoma, non-Hodgkin's lymphomas, and seven other malignancies. Never-married men in the San Francisco Bay area constituted the study population. The pattern of increase in incidence of non-Hodgkin's lymphoma among men aged 25-44 years was similar to that seen for Kaposi's sarcoma; both increased significantly in San Francisco between 1980 and 1985 (p less than 0.001), with an increase among census tracts with high incidence of acquired immunodeficiency syndrome (AIDS) that was greater than the increase seen in other San Francisco census tracts. Among men in tracts with a high incidence of AIDS, non-Hodgkin's lymphoma reached an incidence in 1985 that was five times greater than preepidemic rates. These increased rates support the conclusion of clinical studies that non-Hodgkin's lymphoma is an additional manifestation of AIDS. Similar increases in incidence rates were not observed for other malignancies, suggesting that reports of these malignancies in homosexuals may be isolated incidents. Whether rates of non-Hodgkin's lymphoma will continue to increase and whether rates of other potentially AIDS-associated malignancies will increase in the future may depend on the latency of these malignancies and the survival period of AIDS patients.