Geoscience Reference
In-Depth Information
Chapter 4
Organic Compounds
4.1 Pesticides
Pesticides are substances, or mixtures of substances, intended to prevent, destroy,
repel, or mitigate any pest. They may be chemical substances, biological agents
(such as viruses or bacteria), antimicrobial and disinfectant agents, or other
devices. The term pest includes insects, plant pathogens, weeds, mollusks, birds,
mammals, fish, nematodes (roundworms), and microbes that compete with humans
for food, destroy property, spread or are a vector for disease, or are a nuisance
(EPA
2006
). Pests have attacked and destroyed crops, and pesticides have been
developed, as long as agriculture has been practiced. Some historical examples
include selection of seed from resistant plants in Neolithic times (*7000 BC;
Ordish
2007
), sulfur dusting by the Sumerians (*2500 BC), and over 800 recipes
in the Ebers Papyrus, the oldest known medical document (dated around
1550 BC), which describes recognizable substances that were used as poisons and
pesticides. More recently, during the fifteenth century, arsenic, mercury, and lead
were used to fight pests. The first topic to deal with pests in a scientific way was
John Curtis's Farm Insects, published in 1860, but massive production and
application of pesticides only began around World War II. The major development
at that time was the discovery of the insecticidal properties of DDT by
P. H. Muller in 1942, who received the Nobel Prize (medicine) for his discovery
in 1948.
From this point on, many millions of tons of active ingredients have been
released intentionally each year to the environment, spreading around the globe.
An illustration of the amounts of active-ingredient pesticides applied is shown in
Fig.
4.1
, where total annual amounts used in the USA surpass billions of pounds
for the period from 1982 to 2001.
In contrast to all other groups of contaminants mentioned in Part II, pesticides
are released to the environment in staggering quantities, even though they are
designed to suppress the normal biological growth of different pests. Pesticides
are formulated specifically to be toxic to living organisms, and as such, they are
usually hazardous to humans. In fact, most pesticides used today are acutely toxic
