3. Results
3.1. Pesticide residues in tomatoes
All pesticides analyzed for were detected in the tomatoes. Each of
the organochlorines aldrin, dieldrin, endosulfan, endrin and methoxychlor
were only detected in four or less samples of the 54 analyzed
samples. For heptachlor, however, concentrations above the
LOD and up to 63 μg of pesticide/kg tomato were detected in 46
samples. The geometric mean of all samples and the 95% confidence
intervals were 3.30 (1.81–4.79) μg of heptachlor/kg of tomato
(Fig. 2). There was no significant effect on residue level of either
time or treatment for any of the organochlorines (Table 2). Dieldrin
showed a slight statistical dependence on time, as all four positive
samples were measured at day three.
The organophosphate residues were found inmuch higher amounts
than the organochlorines, with dimethoate, methyl parathion and malathion
being present in concentrations above 1.000 μg/kg (Table 3). All
organophosphate concentrations decreased significantly with time
presenting decay rate constants ranging from 0.42 to 0.82 per day, corresponding
to half times (DT50) of 0.85 to 1.65 days (Tables 2 and 3,
Fig. 2). Washing or peeling also reduced organophosphate concentrations
significantly, except for malathion where processing lowered the
concentrations, although not significantly (Tables 2 and 3).Washing decreased
the concentrations to an average of 54±0.4% (mean±st. dev.)
in day three for dimethoate, malathion, and methyl-parathion, while
chlorpyriphos and ethyl-parathion almost disappeared with washing