Recruiting Strategy and 24-Hour Biomonitoring of Paraquat in Agricultural Workers

ABSTRACT

The objectives of this study were to recruit agricultural workers in Costa Rica to participate in a 24-hour urine collection for paraquat exposure assessment and to compare the 24-hour sampling to end-of-shift sampling. The authors recruited 187 handlers and 54 nonhandlers from coffee, banana, and palm oil plantations. The completeness of 24-hour urine samples collected (a total of 393 samples) was confirmed by questionnaire and urinary creatinine level. For a subset of 12 samples, the absorbed paraquat level was determined in 24-hours and end-of-shift spot urine samples. The participation rate for handlers was ∼90%. The completeness of 24-hour urine collections was verified as the overall average of creatinine levels from 393 urines (1.11 ± 0.50 g/L). A total of 92.4% to 96.7% of urine samples were considered within the acceptable range of urinary creatinine, whereas 94.7% of the samples were described as “complete” from the questionnaire. Measured creatinine correlated well to predicted values (r = .327, p = .0024, 95% CI .12–.51). Detected paraquat levels in spot urine samples had a sensitivity of 96.9% at the high specificity of 100% compared to 24-hour urine samples as the gold standard. There was a significant (p < .0001) correlation between spot and 24-hour urine paraquat levels (r = .7825, 95% CI .61–.88). The recruiting strategy was successful in getting 24-hour urine samples from a farm worker population. Comparison between the paraquat levels in spot and 24-hour urine samples demonstrated that for this compound, end-of-shift spot urine samples would be an appropriate substitute for 24-hour collections.

KEYWORDS:

• biological monitoring
• 24-hour urine
• recruiting strategy
• paraquat
• Agriculture
• farm worker

This work was supported by Syngenta Research Agreement 002994, the Western Center for Agricultural Health and Safety (NIOSH Cooperative Agreement No. U07/CCU9061202), and NIEHS Superfund Basic Research Program, P42 ES004699. However, it has not been subjected to funding agency review and does not necessarily reflect the views of the funding agency.

The authors express many thanks to all the workers' cooperative participation in this study. The authors are also grateful to Dr. Maria Stoecklin-Marois for her study coordination and valuable comments on the manuscript, Dr. Marja Koivunen for her help in obtaining the paraquat data, and Dr. Suzette Smiley-Jewell for editing the manuscript.