The present work was carried out to study the effect of seasonal variations on the levels of pesticide
residues in water, feeds and milk. Our results illustrated that the significantly highest concentrations of
OCs in water and feed were detected during summer [(1.05±0.35, 0.72±0.24, 0.77±0.25, 2.5±0.70 and
0.81±0.27 μg/L, for p.p.DDT, aldrin, β-BHC, lindane and γ.chlordane respectively in water samples)
and (30.0±10.20, 45.00±13.02, 65.33±21.90, 35.33±13.20, 43.67±13.30, 22.00±7.33 and 19.13±8.6 μg
/kg, for p.p.DDD, p.p.DDE, p.p.DDT, aldrin, lindane, γ.chlordane and methoxychlor, respectively in
feed samples) ], while the lowest were detected during spring, on the other hand, none of pesticides
detected in winter which may be attributed to environmental factors. The significantly highest
concentration of diazinon in water and feed was recorded during autumn (78.75±26.30 μg/L and
140.00±64.60 μg/kg, respectively), while the lowest levels were detected during spring. Also, the
highest concentrations of deltamethrin was detected during spring in water (55.30±18.50 μg/L) and
during summer in feed samples (78.40±26.70 μg/kg), while the lowest levels were detected during
autumn in water and during spring in feed samples. The significantly highest concentrations of residues
in milk were detected during summer (p.p.DDD, p.p. DDE, p.p.DDT, heptachlor, heptachlor epoxide,
γ.chlordane, methoxychlor, diazinon and deltamethrin were 20.10±6.01, 52.30±17.20, 33.20±20.06,
1.16±0.38, 6.72±0.90, 2.570±2.23, 0.70±0.20, 58.50±19.20 and 45.13±15.10 μg/kg, respectively) and
the lowest were detected in winter. Our results concluded that the seasonal variations greatly influence
the levels of all examined pesticide residues with variable degree specially diazinon and deltamethrin.