Pesticide Residues in Man - Pesticides: Evaluation of Environmental Pollution - page 508

E/A = 20%-35%; (e) Slight occupational exposure for individuals of E/A = 20%-35%; and
(f) Low occupational exposure for individuals of E/A = < 20%.
Information on the hazard awareness and practice of pesticides among farmers from
other African countries were provided by Williamson et al. (2008). Trends in pesticide use
were surveyed for 45 farmers per crop from Benin, and 25 or 50 farmers from Senegal per
cotton or vegetable field, respectively. Approximately, 56% of the Senegal cotton farmers
corresponding to 86% of Senegal vegetable farmers claimed not using protective cloth-
ing. In case of Benin farmers, only 10%-12% destroy empty the insecticide containers, the
remainder reuse these containers for different purposes, and 2%-8% store the pesticides
in the fields, while the others keep them in bedroom, kitchen, separate store, and under
granary. Health effects of pesticides are negligible for 19%-28% of the Benin farmers.
Comparing results of Williamson et al. (2008) with those of Ibitayo (2006) and Mansour
(2008) may indicate similar attitude of pesticide misuse among the African farmers.
Poisoning surveillance systems are usually maintained only at large urban hospitals.
Village health centers may be completely excluded from monitoring reports. Most of the
severe poisoning cases never reach the hospital and many of those that do are misdiag-
nosed as stroke or respiratory and cardiovascular diseases (Loevinsohn 1987).
Taking into consideration the above mentioned facts, Mansour (2008) has summarized
factors contributing to health risks due to pesticides, especially in developing countries,
into three major items: (1) Factors assigned to governmental authorities; (2) Factors referred
to pesticide users; and (3) Other factors (e.g., malnutrition, infectious diseases, multiple
exposure to toxic chemicals and mixtures, poverty, etc.).
15.8 Factors Affecting Persistence and Fate of Pesticide Residues
When a pesticide is used in the environment, it becomes distributed among four major
compartments: water, air, soil, and biota (living organisms). The fraction of the chemical
that moves into each compartment is governed by the physicochemical properties of that
chemical. The physicochemical properties (e.g., solubility, adsorption, and volatilization),
the environmental conditions (e.g., wind, temperature, and location), and the metabolic
processes all have powerful effects on the persistence and toxicity of the pesticides.
This means that the chemicals released into the environment rarely remain in the form,
or at the location, of release. For example, pesticides used as sprays may drift from the
point of application as air contaminants or enter runoff water as water contaminants.
Many of these chemicals are susceptible to microbial degradation and are rapidly detoxi-
fied, frequently being broken down to products that can enter the carbon, nitrogen, and
oxygen cycles. However, as mentioned before, OCPs are recalcitrant to a greater or lesser
degree to metabolism by microorganisms and persist in soil and water as contaminants.
Moreover, they may enter biologic food chains and move to higher trophic levels or persist
in processed crops as food contaminants (Hodgson 2010).
15.8.1 Physicochemical Factors
Pesticides are distributed in the environment by physical processes such as sedimentation,
adsorption, and volatilization. They can then be degraded by chemical and/or biological
processes. Chemical processes generally occur in water or in the atmosphere and follow