14.4 Problems with Pesticide Use A perfect pesticide would have the following characteristics: Inexpensive Only affect target organisms Short half-life Break down into harmless materials Newer pesticides have fewer drawbacks than early pesticides, but none are devoid of problems.

14.4 Problems with Pesticide Use Persistent pesticides become attached to small soil particles and are easily moved by wind or water. They may be distributed throughout the world from local applications. Persistent pesticides have been discovered in polar ice and are present in detectable amounts in the bodies of animals, including humans, throughout the world.

14.4 Problems with Pesticide Use Bioaccumulation is the process of accumulating higher and higher amounts of material within an organism’s body. Many persistent pesticides are fat soluble and build up in fat tissues. Biomagnification is the process of acquiring increasing levels of a substance in bodies of higher trophic-level organisms. DDT, mercury, and PCBs are all known to accumulate in ecosystems. DDT was banned in the U.S. in the early 1970s.

The biomagnification of DDT

14.4 Problems with Pesticide Use Pesticide resistance is a problem associated with the widespread use of pesticides. Insecticides only kill susceptible individuals. Most surviving individuals have characteristics that allowed them to tolerate the pesticide. Survivors pass on genetic characteristics for tolerance. Subsequent pesticide applications become less effective.

14.4 Problems with Pesticide Use Most pesticides are not species-specific, and kill beneficial species as well as pest species. Many kill predator and parasitic insects that normally control pest insects. Insecticides may change the population structure of the species present so that a species not previously a problem may become a serious pest.

14.4 Problems with Pesticide Use Short-term and long-term health effects are also concerns. Acute poisoning during application sometimes occurs when farmers cannot read caution labels on packaging or do not have access to protective gear. The WHO estimates between 1 million and 5 million acute pesticide poisonings occur annually, resulting in 20,000 deaths.

14.4 Problems with Pesticide Use For most people, the most critical health problem is inadvertent exposure to small quantities. Farmers who were occupationally exposed to pesticides over many years show that they have higher levels of certain kinds of cancers than the general public. Chronic minute exposures to pesticide residues in food or through contaminated environments are also of concern.

14.4 Problems with Pesticide Use A variety of factors is likely to make people in developing countries more vulnerable to the toxicological effects of pesticides: Low literacy and education levels Weak or absent legislative and regulatory frameworks Climate factors that make the use of protective clothing during pesticide application uncomfortable Inappropriate or faulty spraying technology Lower nutritional status (weaker physiological defenses against toxic substances)