ENVIRONMENTAL HEALTH PROFESSION AND ENVIRONMENTAL TOXICOLOGY

Environmental Health is a professional discipline that is directly responsible to the environment. Hence, Environmental toxicology mean everything to the Environmental Health Officer/ Professional/practitioner etc.
To this end, please permit me to share some notes as it concerns Environmental Toxicology (ENTOX) and its importance to Environmental Health profession.

Environmental toxicology, also known as ENTOX, is a multidisciplinary field of science that is concerned with the study of the harmful effects of various chemical, biological and physical agents on living organisms (including man) in their natural environment. Some persons confuse Environmental Toxicology and ECOTOXICOLOGY. They are not exactly the same.

ECOTOXICOLOGY is actually a subdiscipline of Environmental Toxicology that is concerned with studying the harmful effects of toxicants at the population and ecosystems levels.

As a matter of fact, an organism can be exposed to toxicants at various stages of its life cycle but toxicity can vary with the organism's placement within its food web. It is known as BIOACCUMULATION.

Bioaccumulation occurs when an organism stores toxicants in fatty tissues, which may eventually establish a trophic cascade and the Biomagnification of specific toxicants.

Harmful effects of chemicals and biological agents as toxicants from pollutants, insecticides, pesticides and fertilizers can actually affect an organism and its community by reducing its species diversity and abundance. Such changes in population dynamics affect the ecosystem by reducing its productivity and stability.

For purposes of clarity, there are many sources of Environmental toxicity that can lead to the presence of toxicants in our food, water and air. These sources include organic and inorganic pollutants, pesticides and biological agents, all of which can have harmful effects on living organisms and man especially.

They can be called POINT SOURCES of pollution, (for instance the drains from a specific factory). Also, the other, known as NON-POINT SOURCES (ie diffuse sources) like the rubber from car tires that contain numerous chemicals and heavy metals that are spread in the environment.

PCBs (also called POLYCHLORINATED BYPHENYLS): These are organic pollutants that are still present in our environment today, despite being banned in many countries, including the United States and Canada. Due to the persistent nature of PCBs in aquatic ecosystems, many aquatic species contain high levels of this chemical. For example, wild salmon (Salmo salar) in the Baltic have been shown to have significantly higher PCB levels than farmed salmon as the wild fish live in a heavily contaminated environment.

HEAVY METALS:  Heavy metals which are found in food sources such as fish can also have harmful effects. These metals can include MERCURY, LEAD & CADIUM. It has been shown that fish (i.e. rainbow trout) are exposed to higher cadmium levels and grow at a slower rate than fish exposed to lower levels or none. Moreover, cadmium could potentially alter the productivity and mating behaviours of these fish. Heavy metals can not only affect behaviors, but also the genetic makeup in aquatic organisms. Researchers wanted to determine as to what effect metal contamination had on evolutionary responses among populations of yellow perch. Along the gradient, genetic diversity over all loci was negatively correlated with liver cadmium contamination.

PESTICIDES:

These are a major source of environmental toxicity. These chemically synthesized agents have been known to persist in the environment long after their administration. The poor biodegradability of pesticides can also result in bioaccumulation of chemicals in various organisms along with biomagnification within a food web. Pesticides can be categorized according to the pests they target.

1.) INSECTICIDES: Insecticides are are mainly chemical formulations used to eliminate agricultural pests that attack various fruits and crops.

2.) HERBICIDES: Herbicides are also mainly chemical formulations that target herbal pests such as grasses, weeds and other unwanted plants that reduce crop production or provide safe breeding ground for dangerous insects, rodents, reptiles and other pests/vermin's.

DDT

DICHLORODIPHENYLTRICHLOROETHANE: DDT is an organochlorine insecticide that has been banned due to its adverse effects on both humans and wildlife. DDT’s insecticidal properties were first discovered in 1939. Following this discovery, DDT was widely used by farmers in order to kill agricultural pests such as the potato beetle, coddling moth and corn earworm. In 1962, the harmful effects of the widespread and uncontrolled use of DDT were detailed by Rachel Carson in her book The Silent Spring. Such large quantities of DDT and its metabolite Dichlorodiphenyldichloroethylene (DDE) that were released into the environment were toxic to both animals and humans.

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. Furthermore, this effect is amplified when animals who consume the fish also consume the chemical, demonstrating biomagnification within the food web. The process of biomagnification has detrimental effects on various bird species because DDT and DDE accumulate in their tissues inducing egg-shell thinning. Rapid declines in bird populations have been seen in Europe and North America as a result.

Humans who consume animals or plants that are contaminated with DDT experience adverse health effects. Various studies have shown that DDT has damaging effects on the liver, nervous system, and reproductive systems of humans.

By 1972, the United States Environmental Protection Agency (USEPA) banned the use of DDT in the United States. However, despite the regulation of this pesticide in North America, it is still used in certain areas of the world. Traces of this chemical have been found in noticeable amounts in a tributary of the Yangtze River in China, suggesting the pesticide is still in use in this region.

Also, there are still some controversies in Africa and Asia concerning the ban of DDT.

Sulfuryl fluoride

Sulfuryl flouride is an insecticide that is broken down into FLOURIDE and SULPHATE when released into the environment. Fluoride has been known to negatively affect aquatic wildlife. Science had revealed that elevated levels of fluoride has been proven to impair the feeding efficiency and growth of  some marine cratures, especially the common (Cyprinus carpio).
It must be pointed out that exposure to fluoride alters the total protein and lipid levels within these fish as well as ion imbalances, which changes the body composition of the fishes and disrupts various biochemical processes.
-EHSadvisor's Blog