Chemicals in the environment and their health effects

Chemicals in the environment and their health effects DR. SAADIA RASHID TARIQ TENURED ASSOCIATE PROFESSOR DEPTT. CHEMISTRY, LCWU

Chemicals in the environment • Today, globally, chemical pollution has become a serious threat to sustainable development. • Both humanity and ecosystems are suffering from the adverse effects of chemicals either through long-term exposure, low or sub-lethal concentrations of certain chemicals / mixtures of chemicals. • Becoming economically sound by doing less effort, has become a prime focus today all over the world. • The contamination of aquatic environments by pesticides mainly the nitrogen and phosphorous fertilizers are effecting more than 90 per cent of water and aquatic life.

Chemicals in the environment • Recently there was a report of dying of fishes at river Gomti due to poor BOD (Biological Oxygen Demand). • The Oxygen level was decreased because of the contamination due to the dumping of non-degradable waste materials, industry effluents, littering etc. • It has been reported that about 3 % of exposed agricultural workers suffer from an episode of acute pesticide poisoning every year. • Chemicals enter in the air as emissions and in water as effluent.

• The release of chemicals involves many steps in their life cycle. Chemicals in the environment • They begin from the extraction of raw materials - through production chains - transport and consumption - to final waste disposal. • Their distribution sources mainly are through indoor environments, food and drinking water, soils, and water bodies (rivers , lakes etc. ). • Certain long-lived chemicals such as persistent organic pollutants (POPs) and heavy metals are transported globally; reaching otherwise pristine environments such as rain forests, deep oceans or polar regions, and can quickly pass along the food chain, bioaccumulating to cause toxic effects in humans and wildlife. • Boimagnification of DDT (Dichloro diphenyl dichloro ethane ) can be quoted as one of the examples where osprey birds were found to suffer a sharp decline in their population due to increase in its concentration along the food chain through phytoplanktons to zooplanktons and then to fish which was eaten by birds.

ay, in the 21 st century, one of the major environmental lenges lies with the E-waste, which has also become a or threat to all the living systems. found to be the fastest-growing waste stream in the d, with an estimate of 20– 50 million tonnes per year. se E-wastes are of particular interest because it contains ardous substances – such as heavy metals including cury and lead ; Brominated flame retardants (BFRs) ocrine-disrupting substances) and various strategic als ( gold, palladium and rare earth metals ) that can be cled and recovered. Chemicals in the environment

• It is the study of toxic chemicals and their effects/ modes of action. Chemical toxicology • Once they enter our biological system, they disturb the biological process leading in some cases to fatal results. • Some useful and important chemicals are being controlled rigorously as their non-toxicity has not been proved. • Many metals, in spite of being essential dietary trace elements required for normal growth and development of animals and human beings are also listed as environmental hazards. • Even some of the well-known toxic elements Arsenic, Lead and Cadmium are required in trace quantities for the growth of animals. • The major cause of Hemodialysis in patients, is due to use of water containing 100 -1000 ppb of Al(where alum is used in water treatment plants). • In addition biologically inert Aluminum causes brain damage, bone diseases and anemia too in various patient.

Chemical toxicology • The classification of Toxic substances can be done according to their functions and effects. • A chemical which is hazardous as a result of its acute lethal effects can be classified as: • Oral Dose(Through Mouth): If LD 50 < 25 mg/kg is absorbed orally in rat, it is very toxic (R 28). If LD 50 between 25 and 200 mg/kg is absorbed orally in rat, it is toxic(R 25). If LD 50 between 200 and 500 mg/kg is absorbed orally in rat, it is harmful (R 22) 3. • Dermal Dose (Through Skin): LD 50<5 mg/kg percutaneous absorption in rat or rabbit is very toxic (R 27). LD 50 between 50 and 400 mg/kg percutaneous absorption in rat or rabbit is toxic(R 24). LD 50 between 400 and 2000 mg/kg percutaneous absorption in rat or rabbit is harmful (R 21) 3.

• A few of the heavy metals are among the most harmful of the elemental pollutants and are of particular concern because of their toxicities to humans. Heavy metals • These elements are in general the transition metals, and some of the representative elements, such as lead and tin, in the lower right-hand corner of the periodic table. • Heavy metals include essential elements such as iron as well as toxic metals such as cadmium and mercury. • Most of them have a tremendous affinity for sulfur and disrupt enzyme function by forming bonds with sulfur groups in enzymes. • Protein carboxylic acid (–CO 2 H) and amino (–NH 2) groups are also chemically bound by heavy metals. • Cadmium, copper, lead, and mercury ions bind to cell membranes, hindering transport processes through the cell wall. • Heavy metals may also precipitate phosphate biocompounds or catalyze their decomposition.

Arsenic Heavy metals • The main sources of Arsenic are mainly from mining as byproducts, pesticides and chemical wastes and many of its compounds are especially potent poisons. • Many water supplies nearer to mines are contaminated by these poisons. • Arsenic causes harm by disrupting metabolism at the cellular level.

• Cadmium occurs naturally in the earth's crust combined with other elements. Cadmium • Cadmium enter into our body by drinking contaminated water mainly through pipe lines, Metal plating, smoking cigarettes, eating contaminated foods and inhaling it by workers during welding, brazing or soldering processes in factories. • Cadmium can be acutely toxic to freshwater organisms. • On one hand, marine organisms are more resistant to cadmium but people have harmful effects by intake of shellfishes where high concentration of cadmium is present. • In view of biochemical effects of Cadmium, it occurs in nature in association with Zinc minerals. • Growing plants require Zinc and they also take up and concentrate Cadmium with the same biochemical apparatus.

Cadmium • Pollutant cadmium in water may arise from mining wastes and industrial discharges, especially from metal plating. • Chemically, cadmium is very similar to zinc, and these two metals frequently undergo geochemical processes together. Both metals are found in water in the +2 oxidation state. • The effects of acute cadmium poisoning in humans include high blood pressure, kidney damage, damage to testicular tissue, and destruction of red blood cells. • Much of the physiological action of cadmium is attributed to its chemical similarity to zinc. Cadmium may replace zinc in some enzymes, thereby altering the stereostructure of the enzyme and impairing its catalytic activity, causing disease symptoms.

• Cadmium and zinc are common water and sediment pollutants in harbors surrounded by indus- trial installations. Cadmium • Concentrations of more than 100 parts per million (ppm) dry weight sediment have been found in harbor sediments. Typically, during periods of calm in the summer when the water stagnates, the anaerobic bottom layer of harbor water has a low soluble Cd concentration because microbial reduction of sulfate by organic matter, {CH 2 O}, produces sulfide, which precipitates cadmium as insoluble cadmium sulfide: 2{CH 2 O}+SO 42− +H+ → 2 CO 2 +HS− +2 H 2 O Cd. Cl+(chloro complex in seawater) + HS− → Cd. S(s) + H+ + Cl− • Mixing of bay water from outside the harbor and harbor water by high winds during the winter results in desorption of cadmium from harbor sediments by aerobic bay water. This dissolved cadmium is carried out into the bay where it is absorbed by suspended solid materials, which then become incorporated with the bay sediments.

Copper • Copper is an essential trace element. • It mainly comes from industrial and domestic wastes, metal plating, mineral leaching etc. , • It is not very toxic to animals, but toxic to plants and algae at moderate levels.

• Lead is a natural element in the environment. Lead • Human activities results the most of the lead-related health and environmental problems. • The applications of Lead in gasoline, ammunition (household product), and glass manufacturing are very well known. • It is a known persistent bio-accumulative toxic chemical, which means its past uses can continue to expose human beings and other living organisms. • Lead plays important role in impairing brain development and learning’s in children and can affect behavior, growth, high blood pressure and reproduction both in children and in adults. • Similarly animal species are also affected.

Lead • Inorganic lead arising from a number of industrial and mining sources and formerly from leaded gasoline occurs in water in the +2 oxidation state. • In addition to pollutant sources, lead-bearing limestone and galena (Pb. S) contribute lead to natural waters in some locations. • Evidence from hair samples and other sources indicates that body burdens of this toxic metal have decreased during recent decades, largely the result of less lead used in plumbing and other products that come in contact with food or drink. • Acute lead poisoning in humans causes severe dysfunction in the kidneys, reproductive system, liver, and the brain and central nervous system. Sickness or death results. • Lead poisoning from environmental exposure is thought to have caused mental retardation in many children. • Mild lead poisoning causes anemia. The victim may have headaches and sore muscles, and may feel generally fatigued and irritable.

Lead • Except in isolated cases, lead is probably not a major problem in drinking water, although the potential exists in cases where old lead pipe is still in use. • Lead used to be a constituent of solder and some pipe-joint formulations, so that household water does have some contact with lead. • Water that has stood in household plumbing for some time may have elevated levels of lead (along with zinc, cadmium, and copper) and should be drained for a while before use.

• Mercury is highly toxic element. Mercury • It is mostly known as a neurotoxin, meaning that it harms the brain and nervous system. However, mercury is also linked to kidney and liver damage and possibly cancer. • Children are especially at risk because of their brains and bodies are still developing. • Many of the health effects of mercury can be permanent. • When it rains, airborne mercury deposits back on the land water bodies that drain to Puget Sound. • Some of the mercury is converted into methyl mercury, a highly stable compound that contaminates our water and our marine life. • The methyl mercury concentrates up the food chain, especially in certain fish where it can affect the health of people who eat them. • Infants, children and pregnant or nursing mothers must take special precautions to minimize mercury exposure from fish.

Zinc • Zinc can kill young salmon as they swim out of their nest gravel. • In high enough concentrations, zinc can kill many adult fish species.

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