Forensic toxicology is the study of chemicals and medico-legal aspects of these chemicals on the living organisms, which includes studying their toxicological effects, injuries caused, altered physiochemical pathways, etc. These chemicals are mostly drugs like amphetamines, ketamine, alprazolam or controlled substances like alkaloids (morphine, codeine, thebaine, etc.), pesticides (in cases of suicidal, homicidal poisoning or accidental poisoning), heavy metals etc. These chemicals not only interfere with the primary physiological mechanism of human beings but also alters and leads to environmental instability. These chemicals are potent enough to cause damage to the natural environment. Here, forensic, environmental toxicology comes into play. It is the study of the effects of chemicals, i.e. natural and humanmade on the organisms found in the natural environment and their health. Planet earth is the home which houses all forms of living (biotic) and non-living(abiotic) species, and these all forms of lives live co-dependently. Moreover, the human race needs environmental stability the most for its survival because we derive raw material for food from plants and animals. In contrast, plants live independent of the human race; they prepare their food via photosynthesis. 

Humans are frequently in contact with the chemicals directly or indirectly. Natural environmental toxic elements might come into our contact via Food and Drinks. This vulnerability of human wellbeing answers the importance of controlling the toxicity level of the environment. 

One of the significant threats to the environment is PESTICIDES. These are the chemicals used to kill the insects/pests that deteriorate the crops and make them unfit for consumption. Also, the yield is affected, which ultimately affects the life of farmers and their livelihoods. But these chemicals are hazardous for the environment as they get accumulated in the soil and remains as such (undegraded) for several years. This accumulation, when reaches above the permissible limit, causes deterioration of the natural flora and fauna. These chemicals can also seep into the water bodies like seas, estuaries, ponds.

Moreover, it can cause an explosion in ecosystem stability. Say, for example, Pesticide ‘A’ kills a keystone specie of a pond, then the whole of the ecosystem will be destroyed. DDT (dichlorodiphenyltrichloroethane) is an organochlorine class of pesticide which shows biomagnification i.e. keeps on accumulating in the fatty tissues of living organisms in a food chain and is not broken down easily via metabolic pathways. It is a persistent organic pollutant. DDT usage was banned as it led to the fall in the population of various types of birds and many pests developed resistant towards it. The main reason for the fall was the thinning of eggshells because DDT interfered with the calcium metabolic pathways of the organisms which were responsible for the rigidity and maintenance of the eggshells. The eggs used to break when the bird would sit on the eggs for its maturation, or it was also said that these birds used to find omelets in their nests. Hence DDT was banned after the path-breaking dangers highlighted by Rachal Carson in her book “SILENT SPRING” 1972 which resulted in the establishment of the EPA- environmental protection agency. 

Another chemical ALDRIN classified under class 2B highly hazardous chemical by WHO is an organochlorine (subcategory- cyclodienes). It is highly toxic and persists in the environment for almost three decades, putting it into the category of POP, i.e. persistent organic pollutants. It was used for the prevention of insects and other pests from destroying the vegetables, foliage and food-producing crops. It also found its use in termite eradication and homes against vector-borne diseases like Malaria. It is both occupational as well as an environmental pollutant.  Aldrin on exposure to the environment readily gets converted to dieldrin which persists in nature. The persistence results from its lipophilic properties and if ingested gets accumulated/deposited in the fatty tissues of the organisms. The mechanism of action of this pesticide shows that it affects the GABA type A receptors and disrupts the signaling by preventing chlorine influx. Therefore, causes CNS instability such as neurotoxicity, seizures excitation in human beings and animals.

The lethal dose (LD50) of aldrin in Rana hexadactyla (amphibian) was reported to be 2.4ppm. In fish, Saccobranchus fossilus the LD50 was found to be 0.44ppm. So, the dose varies according to the species. It is more toxic than DDT. Lindane but less toxic than drins (isodrins, endrins). Aldrin affects Zebrafish severely even at deficient concentrations i.e.0.01ug/l. It causes oxidative stress in the fish and also decreases superoxide dismutase activity. In eel, Anguilla Anguilla lipidosis occurs and in teleost fish aldrin disturbs the reproductive processes. In rats, the dose 20-70 mg showed an increase in body weight and mortality with repeated doses at 300pmm of aldrin. For humans, the lethal dose is 5g.

Now if we talk about another category of toxicant that majorly takes part in deteriorating the natural environment has to be Heavy metals. These heavy metals can come into the environment via industries, unchecked and untreated waste of laboratories, agricultural wastes, fertilizers, anthropogenic activities, etc. posing a threat to life, be it animals, humans or plants. Heavy metals like ARSENIC, LEAD, CADMIUM, NICKEL, MERCURY, etc. are highly toxic at even very minute quantity. Heavy metals are toxic as they do not undergo any metabolism and gets accumulated in fatty cells. These enter into the human body via air, food, water, or due to occupational exposure. When the metal toxicity reaches more than what can be handled by the environment, hazardous effects breakout. Soil, water and air are the significant environmental aspects being affected by heavy metals. 

They were taking each aspect one by one. These heavy metals are nondegradable and hence stay as such in the soil, which means there will be taken up by the plants and transferred into the food chain. Therefore, impacting the entire ecosystem. The soil has been found to be the major sink for the heavy metal dumping via all the sources of the pollutant. In water bodies, the heavy metals might seep through the soil, runoff from industries, municipalities, etc. and end up accumulating in the sediments of water bodies and the species residing in it. The toxicity levels will be found to be highest in humans because they are the highest-level consumers. Minamata disease is one of the examples of mercury poisoning due to the ingestion of fishes contaminated with methylmercury in Japan.

Now coming to effects on air, industrialization and urbanization have increased the air pollution levels. Air pollution can lead to respiratory infections, increased premature mortality and cardiovascular disease. These pollutants also cause eutrophication, acid rain, corrosion and deterioration of properties.

Conclusively, we all need to protect our environment more than anything because that is the basic necessity for the survival of all forms of life. Forensic, environmental toxicology thus plays a vital role in keeping checks on that.

References:

Reena CJ, MS. Dahiya, Rakhi A. Forensic Toxicology Research to Investigate Environmental Hazard. J Forensic Sci & Criminal Inves.2017;3(2) :10.19080/JFSCI.2017.03.555610.

https://www.intechopen.com/books/heavy-metals/environmental-contamination-by-heavy-metals

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1518881/

https://scialert.net/fulltext/?doi=rjet.2011.81.96

AUTHOR

SWETA

LNJN, National Institute of Criminology and Forensic Science