Uses and Environmental Pollution of Biocides - Pesticides: Evaluation of Environmental Pollution - page 13

from crops and agricultural soils, wind erosion of contaminated soils, and emissions from
manufacturing and disposal processes constantly add to the level of pesticides in the atmo-
sphere. Both direct and indirect sources and other routes play important roles in pesticidal
contamination of the major components of the environment.
The environmental dynamics of pesticides are influenced largely by the various factors
operating in the environment and the physicochemical and biological properties of pesti-
cides. In the broad sense, the environment is divided into four major components, namely
atmosphere (air), hydrosphere (water), lithosphere (soil), and biosphere (biota), each pos-
sessing its own physical and chemical and/or biological properties. The biotic and abi-
otic elements in each component influence the dynamics of pesticides. The environmental
dynamics of pesticides are further influenced by the physicochemical properties of pesti-
cides. Such properties of pesticides as hydrophilicity or lipophilicity, partition coefficients,
adsorption, vapor pressure, and volatility determine the ultimate fate of pesticides in the
living and nonliving portions of the systems. This part will be explained in more details
in Chapter 2.
Trans-boundary transport of chemicals is known since long ago. Once applied, pesti-
cides disperse from the point of application and become redistributed, some on a global
scale. Organochlorine insecticides such as DDT have been detected in the Arctic as well as
in the mid-Pacific Ocean. They are long lived and spread through the atmosphere mostly
as spray drift, which adheres to dust and is transported thousands of kilometers by global
wind currents.
Outside the food chain, the atmosphere is probably the most important medium for
long-distance dispersal of pesticides. Prevailing air currents may transport these pesti-
cides and their alteration products over a great distance (Wolfe 1979).
Pesticides belong to the category of semivolatile organic compounds and can be trans-
ported owing to their aerial/particulate distribution into the atmosphere (Valavanidis 2000).
In this manner, pesticides used in one country may reach another in which their use has
been banned. Pesticide residues may return from the atmosphere to the surface of Earth by
way of rainout, fallout, or direct sorption. In largely agricultural regions, pesticides in the
ambient air may constitute a major source of exposure for human beings and wildlife. On a
global scale, airborne pesticides may affect the ecological balance in nonagricultural areas.
1.3 Unavoidable Cost
Although the use of synthetic chemical pesticides is unavoidable, the extensive consump-
tion not only constitutes a massive loss of money but also causes a lot of undesirable side
effects on human health, environment, food quality, and biodiversity. Pesticide drift occurs
when pesticides suspended in the air as particles are carried by wind to other areas, poten-
tially contaminating them. It has been reported that over 98% of sprayed insecticides and
95% of herbicides reach a destination other than their target species, including nontarget
species, air, water, and soil (Miller 2004). Pesticides are one of the causes of air and water
pollution, and some pesticides are considered POPs and contribute to soil contamination.
Some pesticides, even though no longer used, nevertheless, persist in the environment.
Residues of these pesticides are sometimes found on food grown on contaminated soil or
in the fish that live in contaminated waters. Chlorinated pesticides have been implicated
in a variety of human health issues and as causing significant and widespread ecosystem
disruption through their toxic effects on organisms.