Assessment of DNA damages in lymphocytes of agricultural workers exposed to pesticides by comet assay in a cross-sectional study

Figures & data

Figure 1. Analysis of the image of a comet. (a) Head DNA; (b) tail DNA; (c) head area; (d) tail area; (e) head radius; (f) tail length.

Figure 2. Classes of DNA damage. Source: Waters DJ et al. (2007).

Table 1. General characteristics of the two groups.

	Exposure groups
	1 (n = 1122)		0 (n = 1252)		Total (n = 2374)
	n	%	n	%	n	%	Pearson’s chi-square	p
Age (years)
≤38	96	8.6	475	37.9	571	24.1	–	–
38–51	533	47.5	196	15.7	729	30.7	–	–
>51	493	43.9	581	46.4	1074	45.2	409	0.000
Sex
Females	49	4.4	126	10.1	175	7.4	–	–
Males	1073	95.6	1126	89.9	2199	92.6	28	0.000
Smoking habits
No smokers	727	64.8	1108	88.5	1835	77.3	–	–
Smokers	395	35.2	144	11.5	539	22.7	189	0.000

Figure 3. Fluorescence microscopy images of cells corresponding to some pesticide exposed subjects.

Figure 4. Fluorescence microscopy images of cells of some controls.

Figure 5. Untransformed and log-transformed distributions of comet assay parameters.

Figure 6. Regression line between Exposure increasing values of pesticides exposure and Tail Moment (Ln). (F = 152.29; p(F) = .000; Adj R² = 0.1307; t = 12.34; p(t) = .000; β = 0.20).

Figure 7. Correlation matrix of log transformed parameters measured by means of comet assay. TMln: tail moment[ln]; HDln: head DNA[ln]; TDln: tail DNA[ln]; OMln: olive moment[ln]; HAln: head area[ln]; IIln: Integral Intensity[ln]; HRln: head radius[ln]; TLln: tail length[ln]; TAln: tail area[ln]; SCln: score[ln].

Table 2. Risk (OR) to observe values of comet parameters above the 75th percentile.

		Exposure (score > 1)
		1 (n = 1122)	0 (n = 1252)	OR	LIC (95%)	LSC (95%)
Tail moment (>0.42)	1	459	134	5.77	4.63	7.21
	0	663	1118	–	–	–
Tail area (>212.67)	1	547	136	5.63	4.53	7.03
	0	665	1116	–	–	–
Head DNA (>99.37)	1	105	490	0.16	0.12	0.2
	0	1017	762	–	–	–
Tail DNA (>9.87)	1	458	135	5.07	4.58	7.12
	0	664	1117	–	–	–
Integral intensity (>593)	1	312	282	1.32	1.09	1.6
	0	810	970	–	–	–
Head radius (>14.76)	1	49	547	0.05	0.04	0.08
	0	1073	705	–	–	–
Tail length (>4.42)	1	481	132	6.36	5.1	7.95
	0	641	1120	–	–	–
Olive moment (>0.88)	1	446	145	5.03	4.06	6.25
	0	676	1107	–	–	–
Head area (>779)	1	48	546	0.05	0.04	0.07
	0	1074	706	–	–	–

Table 3. Adjusted risk estimates (ORs) by confounding variables (age, sex and smoking habits) by means of unconditional logistic regression models.

Dependent variables	Independent variables	Odds ratio	SE	Z	p > z	95% CI		LR chi^2 (4)	p > chi^2	Log likelihood	Pseudo R^2
Tail moment	Exposure score	4.61	0.43	16.32	0.000	3.84	5.54	327.67	0.00	–1454.29	0.10
	Age	1.22	0.07	3.24	0.001	1.08	1.39	–	–	–	–
	Sex	1.59	0.29	2.53	0.012	1.11	2.29	–	–	–	–
	Smoking habits	0.70	0.85	–2.87	0.004	0.55	0.89	–	–	–	–
Tail area	Exposure score	2.46	0.22	10.01	0.000	2.06	2.94	125.35	0.00	–1582.86	0.03
	Age	0.80	0.05	–3.63	0.000	0.71	0.9	–	–	–	–
	Sex	1.02	0.17	0.13	0.894	0.73	1.43	–	–	–	–
	Smoking habits	0.62	0.07	–4.04	0.000	0.49	0.78	–	–	–	–
Head DNA	Exposure score	0.27	0.02	–14.17	0.000	0.64	0.82	270.05	0.00	–1510.50	0.08
	Age	0.72	0.04	–5.17	0.000	0.64	0.82	–	–	–	–
	Sex	0.79	0.13	–1.33	0.182	0.56	1.11	–	–	–	–
	Smoking habits	1.27	0.15	2.02	0.043	1.01	1.61	–	–	–	–
Tail DNA	Exposure score	3.61	0.32	14.12	0.000	3.02	4.30	269.68	0.00	–1510.68	0.08
	Age	1.37	0.08	5.21	0.000	1.22	1.55	–	–	–	–
	Sex	1.23	0.21	1.24	0.215	0.88	1.72	–	–	–	–
	Smoking habits	0.79	0.09	–1.94	0.053	0.62	1.01	–	–	–	–
Integral intensity	Exposure score	1.35	0.11	3.47	0.001	1.14	1.60	55.74	0.00	–1617.66	0.01
	Age	0.74	0.04	–4.91	0.000	0.66	0.84	–	–	–	–
	Sex	1.65	0.28	2.88	0.004	1.17	2.33	–	–	–	–
	Smoking habits	1.19	0.13	1.56	0.118	0.95	1.49	–	–	–	–
Head radius	Exposure score	0.17	0.01	–18.22	0.000	0.14	0.21	441.36	0.00	–1424.82	0.13
	Age	0.82	0.05	–3.02	0.003	0.72	0.93	–	–	–	–
	Sex	1.28	0.22	1.42	0.154	0.9	1.81	–	–	–	–
	Smoking habits	0.87	0.10	–1.10	0.273	0.68	1.11	–	–	–	–
Tail length	Exposure score	4.61	0.43	16.32	0.000	3.83	5.54	327.67	0.00	–1454.29	0.10
	Age	1.22	0.07	3.24	0.001	1.08	1.39	–	–	–	–
	Sex	1.59	0.29	2.53	0.012	1.11	2.29	–	–	–	–
	Smoking habits	0.70	0.08	–2.87	0.004	0.55	0.89	–	–	–	–
Olive moment	Exposure score	3.30	0.29	13.18	0.000	2.76	3.94	243.48	0.00	–1523.13	0.07
	Age	1.44	0.08	6.01	0.000	1.28	1.63	–	–	–	–
	Sex	1.47	0.25	2.26	0.024	1.05	2.05	–	–	–	–
	Smoking habits	0.68	0.08	–3.20	0.001	0.54	0.86	–	–	–	–
Head area	Exposure score	0.22	0.02	–16.12	0.000	0.18	0.27	416.68	0.00	–1437.17	0.12
	Age	0.77	0.04	–4.03	0.000	0.68	0.87	–	–	–	–
	Sex	1.30	0.22	1.55	0.121	0.93	1.83	–	–	–	–
	Smoking habits	0.60	0.07	–3.96	0.000	0.47	0.77	–	–	–	–

Table 4. Sensitivity, specificity and predictive positive value (PPV) of the comet assay toward the pesticide exposure.

		Exposed to pesticides (score ≥ 1)
		+	−	Total
Comet assay	+	459	134	593
	−	663	1118	1781
	Total	1122	1252	2374

Sensitivity (41%); specificity (89%); PPV (77%).

Waters, D.J., et al. 2007. Non-invasive prediction of prostatic DNA damage by oxidative stress challenge of peripheral blood lymphocytes. Cancer epidemiology biomarkers & prevention, 16(9), 1906–1910.

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