As because it was toxic to a wide range

As Earth’s population grows, so does the demand for food,
and use of pesticides have become more prominent with this demand. In 1939,
Swiss chemist, Paul Muller, discovered a synthetic, organic, pesticide called dichlorodiphenyltrichloroethane,
or DDT. This chlorinated hydrocarbon was popular because it was toxic to a wide
range of insect pests, yet appeared to have a low toxicity to mammals. DDT was thought
to be persistent, meaning it did not break down rapidly in the environment;
therefore, reapplication was not often necessary, as it was insoluble and did
not wash off in rain or other weather conditions. Over time, it was discovered
that many insects had developed resistance to DDT, and DDT did pose to be
harmful to the ecosystem. This discovery created wide public interest and people
became aware of the chemicals polluting the environment, and as a result, DDT
was banned in North America and other countries in the early 1970’s. Though
pesticides may decrease the number of insects, it has been proven that they are
detrimental to animals, humans, and the environment.

The publication of Rachel Carson’s book, Silent Spring, in 1962 really helped launch
the environmental movement on the dangers of DDT and effects on the
environment. Carson was a scientist who issued grave warnings about pesticides,
and predicted massive destruction of the planets fragile ecosystems. Through
this discovery, her work allowed society to re-evaluate DDT’s use in the environment,
and it was discovered that DDT was linked to the deaths of non-targeted
creatures, like birds. Many pesticide manufacturers argued with this theory,
and stated that small doses of the pesticide did not have any great effect on
the environment. Through Carson’s experimental work, it was proven that even
the smallest amounts of pesticide could affect the survival and reproduction of
species. More importantly, her research demonstrated that, although
concentrations were very low in the soil, atmosphere, and water, concentrations
were higher in plants, higher still in herbivores, and still higher as one moved
up the food chain.

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As a result, many species of birds were becoming endangered
due to bioaccumulation, an increase in concentration of a pollutant from the
environment to the first organism in a food chain, and biomagnification, an
increase in concentration of a pollutant from one link in a food chain to
another. The concern about these phenomena are even small concentrations of
chemicals in the environment can find their way into organisms in high enough
dosages to cause problems. In order for biomagnification to occur, the
pollutant must be, long-lived, mobile, soluble in fats, and biologically
active. DDT is highly persistent in the environment, having a reported
half-life of 2 and 15 years. When Carson made her discoveries, it was proven
that DDT harms animals as it travels up the food chain. Since DDT is not
excreted, her findings show that DDT is not excrete in watery urine, but
accumulates in the fat of animals, and the transfer of energy from lower to
higher trophic levels is extremely efficient, herbivores must eat large
quantities of plants, and carnivores must eat herbivores, and the food chain
continues. An example of this chain reaction would be when 1000 kilograms of
fish containing pesticides are eaten by 90 kilograms of fish-eating birds, the
pesticide levels in the fish-eating birds would be much higher.

After thorough research of the effects of DDT on animals,
the toxicity of the actual chemical must be taken into consideration. The toxicity
of pesticides to wildlife depends on several factors, such as dose, time and
duration of application, all play an important role in a pesticides toxicity.

For example, wildlife are more susceptible to pesticide effects during nesting,
nursing, or during times of low food availability. It also depends on how
wildlife has been exposed to it. Primary exposure includes eating, drinking,
preening feathers, skin contact, exposed carcasses, or feeding upon insects. If
levels are high enough, wildlife will die suddenly. Due to these occurrences,
new pesticides have been developed, and these chemicals are not as persistent
in the food chain, but some have more of a toxicity level, and have more of an
immediate danger to wildlife. Through new discoveries, high concentrations and
long-term exposures, may be linked to cancers, reproductive abnormalities, and
other human and mammalian effects.  

Although these insecticides were developed to rid the world
of harmful insects, they have had a much greater effect on humans. Evidence collected
in the 1950’s and 1960’s shows that DDT was beginning to accumulate in humans.

DDT enters the body when a person eats contaminated foods, but the
concentration depended on the amount of concentration of the chemical and the
amount eaten. Small amounts may also be breathed in and absorbed into the skin.

DDT also attaches to particles which are usually too large to pass through the
lungs into the body, it is more likely carried upward in the mucus and then
swallowed. Once inside the body, DDT stores itself in the fatty tissues, and
leave the body slowly through urine, and breast milk. These levels in the fatty
tissues may remain relatively the same over time, or increase with continued
exposure. Carson’s work has continually sparked scientists research of the
effects of DDT to current day, and it shown that humans may develop different
types of cancers, decreased immune function, and chemical sensitivity.

Throughout history studies have shown the chemical DDT have
both negative and positive effects. Unfortunately, the negative has outweighed
the positive, and as a result, society has gone through many scientific
discoveries with regards to these pesticides. With Carson’s help, scientists
have discovered how DDT has caused many sever problems with the ecosystem, and
threatened not only wildlife, but human lives too. Although DDT still remains
within the environment, populations are no longer decreasing in great
quantities; however, the environmental problems they caused have created a
decrease in populations within the ecosystem. Carson’s movement caused
pesticides to be more strictly regulated, and some are safer to use. With these
positive and negative effects, pesticides today, are soluble in water, can
break down within the soil, and animals are able to break them down in their
livers and through excretion. Rachel Carson was able to expose these dangers
through her book, and spark an environmental movement with the dangers of synthetic
chemicals to the environment and the human race. She advocated that humanity
should learn to coexist with the environment, and not dominate, and her book
increased environmental awareness and allowed people to understand the delicate
balance of the ecosystem.