Shankar IAS Summary Environment Issues and Health Effects - Famous Books

Table of Contents
1. Toxicology Effects
2. Iodine-131
3. Heavy Metals
4. Persistent Organic Pollutants and Pesticides
5. Lead in Paints
6. Dietary and Consumer Hazards
7. Diseases and Syndromes Caused by Environmental Pollution
8. Policy, Programmes and Institutional Measures
9. Bioassay
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Toxicology Effects

Eco-toxicology is the study of the effects of released pollutants on the environment and on the biota that inhabit it. It examines how chemicals, radioactive materials and other pollutants affect individuals, populations and ecosystems, and how those effects propagate through food chains and ecological networks.

Key concepts

• Toxicity - the inherent capacity of a substance to produce harmful effects in a living organism.
• Exposure - the contact between a chemical or physical agent and an organism (dose, duration, route such as inhalation, ingestion or dermal).
• Bioaccumulation - the process by which a substance builds up in an organism over time, because intake exceeds elimination.
• Biomagnification - the increase in concentration of a substance in organisms at higher trophic levels of a food chain.
• LD50 - the median lethal dose; the dose of a chemical that kills 50% of a test population, commonly reported in mg/kg body weight and used to compare acute toxicity.

Rem (radiation dose unit)

Rem gives an indication of biological damage from ionising radiation. It is an estimate of the amount of radiation of any type that produces the same biological injury in humans as that resulting from the absorption of a given amount of X-ray or gamma radiation. Rem (or its SI counterpart sievert, Sv) relates absorbed dose to biological effect through weighting factors for radiation type and tissue sensitivity.

Iodine-131

• Iodine-131 released during nuclear tests or accidents can deposit on vegetation and enter the food chain; it commonly appears in milk of cattle that consume contaminated vegetation and can thereby be passed to humans.
• Iodine-131 concentrates in the thyroid gland and may cause serious damage, especially in children. Post-exposure thyroid monitoring and administration of stable iodine (potassium iodide) are commonly used protective measures in nuclear emergencies.
• Radioactive elements such as strontium and radium tend to concentrate in bone; long-term radioactivity from these radionuclides in the human body is predominantly found in the skeleton.

Heavy Metals

Lead

• Lead is highly toxic to plants, animals and humans and disproportionally affects children (greater absorption and developing nervous system).
• Lead poisoning produces a range of effects including liver and kidney damage, reduced haemoglobin synthesis (anaemia), neurodevelopmental impairment in children and reproductive abnormalities.
• Common clinical and occupational presentations include gastrointestinal disturbances, neuromuscular problems (lead palsy producing muscle weakness and atrophy) and central nervous system involvement that may lead to delirium, convulsions, coma and death in severe cases.
• Sources of lead exposure include leaded paints, contaminated dust and soil, some industrial emissions, leaded petrol residues (historically) and certain consumer products.

Mercury

• Mercury is among the most toxic heavy metals for aquatic ecosystems and human health. In aquatic environments it is often transformed by microorganisms into methylmercury, a highly bioavailable and persistent organic form that biomagnifies in food chains.
• Methylmercury exposure causes severe neurological damage; inhalation of mercury vapour can be fatal at high exposures.
• Historical incidents (for example, Minamata disease) demonstrate catastrophic human and wildlife effects of industrial mercury discharges.
• Small quantities of mercury released from consumer items (thermometers, fluorescent lamps/CFLs) are environmentally significant because of persistence and potential conversion to methylmercury.

Fluorine (fluoride)

• Fluoride occurs naturally in air, soil and water. Elevated fluoride concentrations in drinking water cause health problems collectively termed fluorosis.
• Dental fluorosis presents as staining and mottling of teeth. Skeletal fluorosis causes joint stiffness, pain in bones and joints, spinal deformity and changes in bone structure; in severe cases it can lead to restricted joint mobility and deformities such as valgus or varus deformities of the legs.
• In livestock, excessive fluoride intake causes dental abrasion, lameness and reduced milk production.

Persistent Organic Pollutants and Pesticides

DDT and other organochlorines

• Toxic pesticides such as DDT, BHC and PCBs are persistent organic pollutants: they are resistant to degradation and remain in the environment for long periods.
• Repeated application increases their concentration in soil and water and enables bioaccumulation and biomagnification up the food chain, affecting fish, birds and humans.
• DDT and similar compounds can act as endocrine disrupters, altering activity of hormones such as oestrogen and testosterone and affecting reproduction and development in wildlife and humans.
• DDT was widely sprayed for vector control (for example, marshland mosquito control) and agricultural use; its persistence in ecosystems led to bans or strict controls in many countries.

Pesticide residues in humans

• Surveys in agricultural regions have detected multiple pesticide residues in human blood samples, indicating occupational and environmental exposure pathways.
• Pesticide exposure is linked to acute poisoning incidents, chronic neurological and reproductive effects and increased long-term disease risks depending on the compound and exposure level.

Testing pesticide toxicity

• All pesticides are tested to establish toxicity and to estimate safe exposure levels. Toxicity testing typically uses laboratory animals (mice, rats, rabbits, dogs) and examines acute, subacute and chronic effects as well as reproductive and developmental impacts.
• LD50 (lethal dose for 50% of test animals) is a common measure of acute toxicity: lower LD50 indicates higher acute toxicity.
• Example comparison: DDT had an LD50 of about 113 mg/kg in standard tests, whereas monocrotophos has an LD50 around 14 mg/kg; therefore monocrotophos is markedly more acutely toxic on an LD50 basis.
• Toxicity assessments are then extrapolated, with uncertainty factors, to derive allowable exposure limits for humans and to guide regulatory controls.

Lead in Paints

• Lead compounds have traditionally been used as pigments and drying agents in paints.
• Many countries have restricted or banned lead in household paints because of the risk to children; where regulation is absent or weak, manufacturers may continue to use lead for cost or performance reasons.
• Inhalation or ingestion of lead dust or paint chips (for example from deteriorating paint or renovation activities) is a common exposure route, especially for children, and can lead to developmental neurotoxicity.
• Alternatives to lead pigments exist, but switching may increase cost and require reformulation to achieve comparable paint performance; regulatory action and market incentives have reduced lead paint use where enforcement exists.

Dietary and Consumer Hazards

Trans fats

• Trans fatty acids are formed during partial hydrogenation of vegetable oils; hydrogenation increases shelf life and stability against rancidity and is used in products such as vanaspati and many processed foods.
• Trans fats are associated with increased risk of coronary heart disease, adverse effects on blood lipids, and links to other conditions such as diabetes; public health authorities recommend minimising trans fat intake.
• Regulatory actions have included labelling requirements and limits on trans fat content; consumers are advised to read labels and prefer products with low or zero trans fats.

High caffeine in energy drinks

• Energy drinks have attracted controversy because of high caffeine content and aggressive marketing as instant energy sources.
• Many brands contain high levels of caffeine (reports indicate some formulations had levels up to several hundred ppm), together with sugar, taurine, glucuronolactone, vitamins and herbal extracts.
• The immediate sensation of increased alertness after an energy drink is largely due to caffeine and sugar; physiological energy comes from caloric intake (sugars) and metabolic processes.
• Regulation historically fell under food safety and adulteration laws. Amendments and regulatory reviews have sought to cap caffeine levels in certain beverages and to require labelling of stimulant content.
• Regulatory developments have varied by jurisdiction and companies have at times sought legal remedies against specific amendments; food safety authorities continue to develop standards and labelling requirements for energy drinks to protect consumers.

Diseases and Syndromes Caused by Environmental Pollution

Minamata disease

• First identified in Minamata city, Kumamoto Prefecture, Japan, in 1956.
• Caused by release of methylmercury in industrial wastewater from the Chisso Corporation chemical factory (discharges from 1932 to 1968 were implicated).
• Minamata disease is a neurological syndrome due to severe mercury poisoning, causing sensory disturbance, ataxia, visual and hearing impairment, speech difficulty and, in severe cases, death.

Yokkaichi asthma

• Occurred in Yokkaichi, Mie Prefecture, Japan between about 1960 and 1972.
• Industrial combustion of petroleum and heavy oil released large quantities of sulphur oxides and particulates, creating severe air pollution and smog that produced chronic respiratory disease described as Yokkaichi asthma.

Itai-itai disease

• Documented in Toyama Prefecture, Japan from the early 20th century, with major recognition around 1912 onwards.
• Caused by cadmium contamination of river water, originating from mining and metal processing, leading to cadmium accumulation in rice and food crops.
• Clinical effects included severe bone pain, osteomalacia (softening of bones), renal dysfunction and eventually disability; itai-itai means "it hurts, it hurts" in Japanese, referring to the bone pain experienced by sufferers.

Blue baby syndrome

• High nitrate contamination of groundwater can lead to methemoglobinaemia in infants (reduced oxygen-carrying capacity of haemoglobin), commonly called blue baby syndrome, and can be fatal if not treated.
• Sources of nitrate contamination include agricultural fertiliser leaching and septic system effluent.

Pneumoconiosis (including black lung)

• Pneumoconiosis refers to lung diseases caused by inhalation and retention of mineral dusts; coal workers' pneumoconiosis (black lung) results from long-term inhalation of coal dust and leads to progressive pulmonary fibrosis and respiratory failure in advanced cases.

Asbestosis

• Asbestosis arises from inhalation of asbestos fibres, causing pulmonary fibrosis, restrictive lung disease and increased risk of lung cancer and mesothelioma in exposed workers.

Silicosis

• Silicosis is caused by inhalation of crystalline silica dust (for example in mining, stone cutting and sandblasting) and leads to nodular pulmonary fibrosis and impaired respiratory function.

Emphysema

• Emphysema is chronic destruction of alveolar tissue causing reduced elastic recoil of the lung and impaired gas exchange; air pollution and cigarette smoke are major risk factors that accelerate the development of emphysema.
• Damage is irreversible and causes progressive shortness of breath and reduced exercise tolerance.

Sick Building Syndrome (SBS)

• Sick Building Syndrome is a set of symptoms (headache, eye/nose/throat irritation, fatigue, dizziness) experienced by occupants of a building, where no specific illness or cause can be readily identified.
• Poor indoor air quality, inadequate ventilation, chemical contaminants from building materials, biological contaminants (mould, bacteria) and ergonomic or psychosocial factors commonly contribute to SBS.

Policy, Programmes and Institutional Measures

National Wastelands Development Board (NWDB)

• The National Wastelands Development Board was established under the Ministry of Environment & Forests in 1985 to increase tree and green cover on wastelands, to prevent productive land from becoming wasteland and to formulate policy, perspective plans and programmes for management and development of wastelands.
• In 1992 the Board was transferred to the Ministry of Rural Development and placed under a new Department of Wastelands Development headed by a Minister of State; the intention was to integrate wasteland reclamation with rural development schemes and local livelihoods programmes.

Bioassay

• Bioassay is a test that uses living organisms to detect the presence, concentration or biological effects of pollutants, toxicants or other environmental disturbances.
• Bioassays are widely used in pollution studies to assess lethality, sublethal effects, behavioural changes and reproductive impacts on test organisms; commonly used organisms include fish, invertebrates, plants and microbial cultures.
• Typical bioassay endpoints include LC50 (lethal concentration for 50% of a test population when exposure is by concentration in water), EC50 (effective concentration producing a specified sublethal effect in 50% of test organisms) and behavioural or physiological indicators.
• Bioassays are used to determine safe concentrations, maximum acceptable toxicant concentrations (MATC) and to inform environmental quality standards and regulatory decision making.

Conclusion

Understanding environmental toxicology requires integrating knowledge of contaminant sources, environmental fate, exposure pathways, biological effects and regulatory responses. Preventive measures-pollution control, safer alternatives, monitoring, labelling and timely public health interventions-are essential to reduce disease burden and protect ecosystems.