Degradation of Pesticides - Pesticides: Evaluation of Environmental Pollution - page 75

TABLE 3.1
Hazardous Effects of Pesticides and Their Degraded Products

Types of Pesticides Hazardous Effects

Dieldrin, BHC, DDT Headache, dizziness, gastrointestinal disturbances, numbness and weakness of the

extremities, apprehension, and hyperirritability
DDT produces serious functional and morphological changes in every organ of the
body; most affected is the nervous system. Metabolites of DDT are carcinogenic

2,4-D and 2,4,5-T Irritation to skin and mucus membranes, vomiting, headache, diarrhea, confusion,

bizarre or aggressive behavior, and muscle weakness

Organophosphate Headache, excessive salivation and tearing, respiratory depression, blurred vision,

cramps, nausea, diarrhea, rapid or slow heart rate, weakness, and giddiness

Carbamate Malaise, muscle weakness, dizziness, sweating, headache, salivation, nausea, vomiting,

abdominal pain, diarrhea, nervous system depression, blurred vision, and weight loss

Pyrethroids Abnormal facial sensation, dizziness, salivation, headache, fatigue, vomiting, diarrhea,

numbness, irritation to skin and upper respiratory tract, and asthma

Stable airborne pesticide residues and their degradation products may move from the
application site and be deposited in dew, rainfall, or dust. This may result in pesticide redistri-
bution within the application site or movement of some compounds off site. Strongly sorbed
and high-persistent pesticides, that is, large t 1/2 values remain near the ground surface for a
long period, increasing the chances of being carried to a stream or lake or into groundwater
via runoff or leaching. Organochlorine compounds, which are highly stable, pose a threat to
nontarget animals inhabiting the water bodies, which can get polluted through groundwater.
Though most of the organochlorine compounds, especially DDT and BHC, have been banned
in the last decade, most of the groundwater samples still contain DDT or BHC or both.
In Table 3.1, some hazardous effects of pesticides and degraded products are depicted.

3.5.1 Adverse Effects

• Some pesticide degradation products show much more toxicity to animals and
humans than the parent compounds (Table 3.1).
• Pesticide degradation products may enhance or decrease microbial population,
inhibiting the growth of one or more specific microbes.
• Sulfonylureas and their degraded products show acute toxicity to the cladoceran
Daphnia magna , a primary consumer in freshwater ecosystems.
• Pesticide degradation products in water may block the action of hormones in fish
and amphibians, causing reproductive dysfunction and abnormal development,
which cause diminishing of productivity and fecundity.

3.6 Conclusions

• Biotic degradation is the major pathway for pesticide degradation in soil and
water, followed by photolysis.
• Oxidation, hydrolysis, reduction, conjugation, and rearrangement are the major
reactions that occur during pesticide degradation.