Agricultural and residential pesticides in wipe samples from farmworker family residences in North Carolina and Virginia - Children's Health

Environmental Health Perspectives, March, 2004 by Sara A. Quandt, Thomas A. Arcury, Pamela Rao, Beverly M. Snively, David E. Camann, Alicia M. Doran, Alice Y. Yau, Jane A. Hoppin, David S. Jackson

Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to evaluate associations between categorical variables--for example, the presence of agricultural pesticides on floors and toys. Multiple logistic regression models were used to predict binary outcome measures; proportional odds models were used to predict ordinal outcome measures. Potential predictors were observed sample characteristics and were included in multiple regression models if p < 0.2 in corresponding simple regression analyses. If two predictors in a model were highly related, then only the one judged to have greater predictive value was included. No interaction terms were included. ORs and 95% CIs from the multiple regression analyses were used to evaluate associations between outcome measures and potential predictors, adjusting for other predictors in the model. Statistical significance was defined as p < 0.05 (two-sided). SAS software (SAS Institute Inc., Cary, NC) was used for all statistical analyses.

Results

Table 1 presents descriptive analysis of the households and their residents. The agricultural and residential pesticides detected in floor, toy, and hand wipes are presented in Table 2. The most commonly detected agricultural pesticides were oxyfluorfen and simazine, and the most commonly detected residential pesticide was trans-permethrin. At least one agricultural pesticide was detected in 18 floor samples (44%), 12 toy samples (29%), and nine hand samples (22%). Twenty households (49%) had at least one agricultural pesticide detected in any location. At least one residential pesticide was detected in 39 households (95%), 39 floor samples (95%), 24 toy samples (58%), and 19 hand samples (46%). Eight homes had a low (0-2) number of pesticides detected, 21 a medium (3-5) number, and 12 a high (6-8) number. No home had more than 8 of a possible 13 residential pesticides detected.

When agricultural pesticide detection was compared among sources within households, there was a strong positive association between detecting agricultural pesticides in toy wipes and detecting them in floor wipes (OR = 13; 95% CI, 2.3-74). There was a similar strong positive association between floor wipe and hand detections (OR = 6.7; 95% CI, 1.2-38). This association was even greater between agricultural pesticides found on floors and in toy or hand wipes combined (OR = 17; 95% CI, 2.9-93). In each case, this estimated OR was > 1 (p < 0.05), which indicates elevated risk, given presence of agricultural pesticide(s) on the floor.

When household pesticide detection was compared among the three sources within households, there was a strong positive association between detecting > 0 household pesticide in toy wipes and detecting > 3 pesticides in floor wipes (OR = 7.0; 95% CI, 1.7-28). There was a similar strong positive association between > 3 pesticides in floor wipes and > 1 pesticides in hand wipes (OR = 7.7; 95% CI, 1.7-34). The association was even greater between residential pesticides found on floors and in toy or hand wipes combined (OR = 12; CI, 2.5-59). Similarly, in each case, the estimated OR was > 1 (p < 0.05), which indicates greater likelihood of pesticides on toys or hand, given presence of > 3 residential pesticides on the floor.

A summary of pesticide loadings is given in Table 2, with values for floors and hands expressed as loadings (micrograms per square meter), and toy wipes expressed as weights (micrograms). There is considerable variability in the loadings or weights of pesticides found on the same surface between different chemicals and within the same chemical.

Among possible predictors of at least one agricultural pesticide detected on any surface sampled (Table 3), two reached statistical significance. An elevated risk of agricultural pesticides was observed given agricultural field adjacent to the house (unadjusted OR = 18; 95% CI, 3.7-88). The association persisted for location adjacent to agricultural field, after adjusting for other possible predictors (adjusted OR = 20; 95% CI, 3.2-126.2). No other predictors were statistically significant in the multiple logistic regression model.

Two of the possible predictors of level of residential pesticides detected on any surface sampled (Table 4) were statistically significant (p < 0.05). Increased odds of a higher number of residential pesticides was associated with houses judged difficult to clean (unadjusted OR = 4.2; 95% CI, 1.2-14.9) and rented housing (unadjusted OR = 4.6; 95% CI, 1.0-21). These two predictors, plus pesticide application work, non-nuclear family, and mobile home were tested in the multiple regression model based on p < 0.2 in the simple regression. An increased likelihood of residential pesticides was observed, given that houses were judged difficult to clean (adjusted OR = 5.1; 95% CI, 1.2-22.4).