DNA damage in B and T lymphocytes of farmers during one pesticide spraying season

Abstract

Purpose: The effect of one pesticide spraying season on DNA damage was measured on B and T lymphocytes among open-field farmers and controls.

Methods: At least two peripheral blood samples were collected from each individual: one in a period without any pesticide application, several weeks after the last use (January, at period P0), and another in the intensive pesticide spraying period (May or June, at period P4). DNA damage was studied by alkaline comet assay on isolated B or T lymphocytes.

Results: Longitudinal comparison of DNA damage observed at both P0 and P4 periods revealed a statistically significant genotoxic effect of the pesticide spraying season in both B (P = 0.02) and T lymphocytes (P = 0.02) in exposed farmers. In contrast, non-farmers did not show any significant modifications. DNA damage levels in B and T lymphocytes were significantly higher in farmers than in non-farmers during the P4 period (P = 0.003 and P = 0.001 for B and T lymphocytes, respectively) but not during the P0 period. The seasonal effect observed among farmers was not correlated with either total farm area, farm area devoted to crops or recent solar exposure. On average, farmers used pesticides for 21 days between P0 and P4. Between the two time points studied, there was a tendency for a potential effect of the number of days of fungicide treatments (r (2) = 0.43; P = 0.11) on T lymphocyte DNA damage.

Conclusions: A genotoxic effect was found in lymphocytes of farmers exposed to pesticides, suggesting in particular the possible implication of fungicides.

Keywords: Comet assay; DNA damage; Lymphocytes; Occupational exposure; Pesticides.

Fig. 1

Variability of the internal standard observed in 56 independent experiments. Experiments were performed from May 2009 to September 2009 by experimenter 1; from January 2010 to February 2010 by experimenter 2; from March 2010 to May 2010 by experimenter 3; and from April 2011 to July 2011 by experimenter 4. One experiment is defined as one electrophoretic run. The two dotted horizontal lines represent the range of mean ± 2 SD, representing an acceptable variability for the comet assay, as previously described (De Boeck et al. 2000). The solid horizontal line in the middle of this range represents the mean of the data. Statistical analyses performed for comparisons of DNA damage levels between non-exposed individuals and farm owners were conducted with and without exclusion of the three experiments, for which the OTM of the standard was higher than this range

Fig. 2

DNA damage on B and T lymphocytes in non-exposed group (a) and farm owners group (b). For both groups, S0 samples were collected at P0 period (January) and S4 samples were collected at period corresponding to the intensive spraying period P4 (May–June). For the farm owners group, another sample (S2 sample) was collected at P2 period (after the first day of spraying season). Boxes are limited by first and third quartiles separated by the median; thin vertical lines represent minimum and maximum values in the 10–90th percentile range. Points are the extreme values. Statistical analysis was performed with paired samples Student’s t test