Environmental toxicants : Source, types and effects

What is Environmental toxicology?

The branch of science deals with the study of harmful effects of chemicals substances, physical substances, and also biological substances on the environment and also on living organisms.

Rachel Carson published the book silent spring in 1962. In which she mentioned the harmful effects of the agents of toxicants and these toxicants are very effective in our lives. And she made this a separate discipline in the field of environmental toxicology and Rachel Carson is known as the mother of environmental toxicology. These toxicants consider as sensitive in some way. She also mentions the consumption of pesticides.

Within its food web toxicity is dependent on the organism. Organisms live in different places and have different effects. Organisms develop toxicity when they accumulate a huge amount of toxicants in their fatty tissue. These accumulations are known as bioaccumulation


Pollutants polychlorinated biphenyls (PCBs)

These consider as the cluster of chemicals which are made by humans. They are liquid and also solid. They have no smell. The Colour is clear and maybe yellow. They are considered very resistant mostly to high temperatures and pressures. Mostly these PCBs are used in electronics such as in capacitors and also in the transformer.

In many countries such as the United States and Canada, these agents are banned but also present in our environment and they are mostly organic. PCBs have persistence. Due to this nature, they affect the aquatic animals and they have a high amount of these agents in their bodies.

For E.g. salmon species have a high level of PCBs.

Heavy metals:

Chemicals elements that may be metallic have high density refer to as heavy metals. These at low concentrations are very poisonous.

E.g. lead, cadmium, mercury, chromium, thallium, arsenic.

In our food materials these metals are common e.g in fishes these are present and these grow at a very slow speed while other fishes that do not have any heavy metals are growing at high speed. These foods ultimately consume as food.

If we work at that places where exposures to these metals are common then we suffer from these heavy metals because when we breathe, if heavy metals are present in the air then these are inhaled by us and affect the lungs.

  • E.g. major factories in the world deal with heavy metals and we expose to these metals.
  • When we construct our house, it uses lead paint which is getting old also a source of heavy metals

Metal toxicity:

Heavy metals like cadmium, chromium, nickel, lead, copper, arsenic, zinc. These metals can destroy the atmosphere and also human health. Although in a low amount these are very effective for health, they need for the body at very low concentration. But as these metals increase at the threshold level them starting causes toxicity. The metals are causing agents of evolutionary changes in the environment and also cause the survival of organisms


In our field, the use of pesticides is very common, and these are also a major source of toxicity. Pesticides are made by humans in labs and they have long-lasting effects on humans’ health and also on the environment.

An organism that consumes these pesticides are faced with bioaccumulation. These pesticides are stored in the human body and remain there for a long time. And there is also the biomagnification of toxic chemicals in the body.

These pesticides become part of the food web different types of pesticides make because it depends on which type of pest we kill.

In crops, we mostly prefer insecticides to reduce the population of the pest. The also weeds are present and also unwanted plants, there is a need to eliminate these agents so then we use herbicides.


Organochlorine insecticides, such as dichlorodiphenyltrichloroethane (DDT), are very toxic agents. Rachel Carson published that this toxic cause very harmful effects on humans and plants.

These toxic chemicals use to kill the pest in crop fields and they cause adverse effects on health so these agents banners in 1962. Because they excrete a large amount of DDE in the atmosphere, there are very harmful to organisms.

DDT has high persistence. They are not easily degradable. They live in soil for a very long time. Aquatic life is very effective from these agents and this DDT store in fish’s bodies. This is the source of biomagnification in the food web.

These fishes consume by various big fish and they also consume those chemicals and stores them in their bodies.

They also have very adverse effects on the lives of birds because birds consume fishes that have this agent. That is why the bird population near sea level reduce.

Sulfuryl fluoride:

It is the chemicals considering as insecticides, before releasing into the atmosphere it reduces into two components one is fluoride and 2nd one is a sulfate.

Researches show that the component fluoride is highly toxic for water living organism. E.g. Cyprinus carpio is also known as common carp that is very effective from these components due to this they reduce the ability of feeding habit.

Whenever any organism exposes to fluoride is facing the problem of ion balancing. And also have a problem with protein and lipid levels. Due to these factors, they face various problems in their biochemical process which takes place in their body.

Cyanobacteria and cyanotoxins

Cyanobacteria blue-green algae and photosynthetic bacteria. They are present in many types of water. These algae growth is related to the high-temperature level and also eutrophication.

Eutrophication is the process in which water has a high level of nutrients and minerals and causes the growth of these algae. It seems that genera of cyanobacteria cause more toxicity.

On the other hand, cyanotoxins are the deals with the toxic of skin, toxic of neurons, toxic of hepatic. Although death from cyanotoxin is very less. They mostly cause allergic reactions in bodies.

Presences of cyanotoxin in water:

 Factor involves who cause toxicity in water;

  1. Directly drink water from sources of water.
  2. Effectiveness of eliminating agents from water sources.

There is no data that tells the amount of toxin in drinking water. The treatment plant that treats the water does tell about how many toxic agents are remaining.

Effects of the toxin on humans

In Australia in 1979, the disease causes by the consumption of water. This is mostly due to a type of cyanobacteria. These cause in organism cylindrospermopsin. This toxin mostly affects the kidney and liver. The kidney damages due to the loss of electrolytes. 

Hazardous wastes:

Hazardous waste plays an important role in spreading toxicity in the environment. It needs to purify every waste before disposal because it becomes the source of pollutants in the environment.

In our society, major sources of hazardous waste are industrial waste because in industry huge amounts of pollutants disposes of every day without treated them so they become major causes of diseases. 

In 1989, the central government made a rule for the management of hazardous waste and it applies in 2000 and 2003. That mostly deals with waste before disposal so that there is no chance of any disease.

These may be in solid and in liquid form and also sometimes in gaseous form. They may collaborate with other material and causes the damage to the atmosphere.

Health effects:

In the whole world, different organizations developing to overcome the problems of waste materials these known as health impact assessments HIA. As we know every type of waste becomes the reason for disease.

In developing countries, various industries disposed of polluting agents in the environment every day they affect adverse damage to the health of humans, plants, and every living organism so there is a need to recycle the waste so that they don’t cause disease in the population.

Wastes of electronics:

In our world, there is a huge demand for use of electronics for their benefits. People in the world depend on this equipment to fulfill their needs so that how much we use these things, according to that waste of electronics also increases. And we consider them a fast-developing waste but municipal solid waste MSW considers 1 % of all the waste.

In electronic heavy metals such as lead, mercury is common to use. When these electronics materials become waste they cause severe damage to health because they have high metals in them.

Routes of exposure:

In plants routes commonly by soil but when we talk about the human there are majorly three ways to exposed with toxicants agents. Then these agents get into the body and cause severe damage to health.

  1. One of the major ways is the respiration process in which we respire all the hazardous waste in our body these chemicals enter the body and cause respiratory problems.
  2. 2nd one is dermatitis means skin routes, and also by eye, in which dangerous chemicals absorb by the skin and cause skin cancer and other severe problems.
  • 3rd most is by getting food, water, which mostly contaminates with toxic substances.

Reviewed by:
Dr. Muhammad Adnan Asghar (Ph.D.)

Chinese Academy of Sciences Fuzhou, Fujian