Environmental Toxicology, is a multidisciplinary
field of science concerned with the
study of the harmful effects of various chemical,
biological and physical agents on living
organisms.
Rachel Carson is considered the mother of
environmental toxicology, as she made it a distinct
field within toxicology in 1962 with the publication of
her book Silent Spring, which covered the effects of
uncontrolled pesticide use.
• Rachel Louise Carson (May 27, 1907 – April 14,
1964) was an American marine biologist and
conservationist whose book Silent Spring and other
writings are credited with advancing the global
environmental movement.
Late in the 1950s, Carson turned her attention to
conservation, especially environmental problems that
she believed were caused by synthetic pesticides. The
result was Silent Spring (1962), which brought
environmental concerns to an unprecedented share of
the American people. Although Silent Spring was met
with fierce opposition by chemical companies, it spurred
a reversal in national pesticide policy, which led to a
nationwide ban on DDT and other pesticides, and it
inspired a grassroots environmental movement that led
to the creation of the U.S. Environmental Protection
Agency. Carson was posthumously awarded the
Presidential Medal of Freedom by Jimmy Carter.
Agent Orange Vietnam War
During the Vietnam War, between 1962 and 1971,
the United States military sprayed nearly
20,000,000 U.S. gallons (75,700,000 l) of chemical
herbicides and defoliants in Vietnam, the goal was
to defoliate rural/forested land, depriving guerrillas
of food and cover and clearing sensitive areas such
as around base perimeters. The program was also
a part of a general policy of forced draft
urbanization, which aimed to destroy the ability of
peasants to support themselves in the countryside,
forcing them to flee to the U.S. dominated cities,
depriving the guerrillas of their rural support base.
The Vietnam Red Cross reported as many as 3
million Vietnamese people have been affected by
Agent Orange, including at least 150,000 children
born with birth defects. According to Vietnamese
Ministry of Foreign Affairs, 4.8 million Vietnamese
people were exposed to Agent Orange, resulting in
4,00,000 people being killed or maimed, and
5,00,000 children born with birth defects.
Environmental Toxicology
• Harmful effects of chemical and biological
agents can include toxins from pollutants,
insecticides, pesticides, and fertilizers all of
which can impact an organism and its
community through shifts in species diversity
and abundance.
• Resulting changes in population dynamics
impact the ecosystem by altering its productivity
and stability.
sources include organic and inorganic
pollutants, pesticides and biological agents
Pollutants Polychlorinated Biphenyls (PCBs) are
organic pollutants
Heavy Metals
These metals
can include mercury, lead, aluminum and
cadmium
Pesticides
These chemically synthesized agents have been known
to persist in the environment long after their
administration
The poor bio-degradability of pesticides
can result in bio-accumulation of chemicals in various
organisms along with bio-magnification within a food
web.
Insecticides
• Dichlorodiphenyltrichloroethane (DDT
DDT
was widely used by farmers in order to kill agricultural
pests.
DDT is not easily biodegradable and thus the chemical
accumulates in soil and sediment runoff. Water systems
become polluted and marine life such as fish and
shellfish accumulate DDT in their tissues
Hazardous wastes