Environmental and occupational health

In short

Environmental health is the branch of public health that deals with the physical, chemical and biological agents in air, water, soil, housing and climate that affect human health; occupational health deals with the same agents plus ergonomic and psychosocial hazards as they arise from work. In India they carry an enormous disease burden — ambient and household air pollution, unsafe water and sanitation, and occupational dust together account for a large share of deaths and DALYs, with air pollution alone linked to over a million deaths a year in Indian burden-of-disease estimates. The subject is examined in BPH/B.Sc Public Health papers on environmental health, occupational health and epidemiology of non-communicable disease, and in competitive exams (UPSC, state health services, NIHFW/AIIMS MPH entrance). It is used daily by public health officers, EHS and HSE executives in factories, municipal health departments, ESIC and state factory inspectorates, NGOs and ESG/sustainability teams.

Explained

Concepts, scope and the exposure–disease pathway

• Environmental health: prevention of disease and injury caused by environmental agents — air, water, soil, food, radiation, noise, vectors, housing, climate. Occupational health (ILO/WHO definition) aims at promotion and maintenance of the highest degree of physical, mental and social well-being of workers in all occupations.
• Three classic objectives of occupational health: adaptation of work to the worker and the worker to the job, protection of workers against health hazards, and placement in an occupation suited to their capacity.
• Source → pathway → receptor chain: emission source, environmental medium (air/water/soil), route of entry (inhalation, ingestion, dermal absorption, injection), target organ, health effect. Control is cheapest and most effective nearest the source.
• Hazard vs risk: a hazard is the intrinsic potential to cause harm; risk = hazard × exposure (probability × severity). Dose depends on concentration and duration, hence time-weighted averages.
• Exposure assessment terms: personal monitoring (breathing-zone sampler), area/static monitoring, biological monitoring (blood lead, urinary hippuric acid for toluene), and biological effect monitoring (blood ZPP, cholinesterase for organophosphates).
• Epidemiological designs used: cross-sectional prevalence surveys of workers, retrospective cohort/mortality studies of exposed industries, case–control studies for rare cancers, and panel/time-series studies of daily air pollution versus hospital admissions. Healthy-worker effect biases occupational cohorts towards apparently lower mortality.

Air: ambient, household and Indian standards

• Primary pollutants: PM10, PM2.5, SO2, NOx, CO, NH3, Pb, benzene, benzo(a)pyrene, As, Ni. Secondary pollutant: ground-level ozone, formed photochemically from NOx + VOCs.
• NAAQS, 2009 (CPCB, notified under the Air (Prevention and Control of Pollution) Act, 1981) prescribes 12 parameters. Key annual/24-hour limits: PM10 60/100 µg/m³, PM2.5 40/60 µg/m³, SO2 50/80 µg/m³, NO2 40/80 µg/m³; CO 2 mg/m³ (8-hour) and 4 mg/m³ (1-hour); O3 100 µg/m³ (8-hour), 180 µg/m³ (1-hour). A revision of NAAQS has been under consideration for several years; quote the 2009 values unless a new notification is cited.
• WHO Global Air Quality Guidelines, 2021 are much stricter (PM2.5 annual 5 µg/m³, 24-hour 15 µg/m³) and are guidelines, not law.
• National Air Quality Index (AQI, 2014): six bands — Good 0–50, Satisfactory 51–100, Moderate 101–200, Poor 201–300, Very Poor 301–400, Severe 401–500 — computed on eight pollutants; the worst sub-index becomes the AQI, requiring at least three pollutants including PM10 or PM2.5.
• Programmes: National Clean Air Programme (NCAP, 2019) targets particulate reduction in non-attainment cities (original target 20–30% by 2024, revised to 40% reduction or meeting NAAQS by 2025–26); GRAP (Graded Response Action Plan) for Delhi-NCR under CAQM; PM Ujjwala Yojana for LPG connections to reduce household air pollution; CNG/BS-VI fuel transition; National Programme on Climate Change and Human Health (NPCCHH) with heat and air-pollution-related illness surveillance.
• Household (indoor) air pollution: biomass and kerosene combustion causes ALRI in children, COPD, lung cancer, cataract, low birth weight. Indoor pollutants also include radon, environmental tobacco smoke, formaldehyde, dampness and moulds. Sick building syndrome is non-specific symptoms relieved on leaving the building.
• Health effects: short-term — exacerbation of asthma, COPD, myocardial infarction, stroke; long-term — lung cancer (PM2.5 and diesel exhaust are IARC Group 1), reduced lung function growth, adverse birth outcomes.

Water, sanitation, waste and vectors

• Water quality: IS 10500:2012 (with amendments) gives drinking water specification — acceptable/permissible-in-absence-of-alternate-source limits, e.g. turbidity 1 NTU, pH 6.5–8.5, total hardness 200/600 mg/L, fluoride 1.0/1.5 mg/L, nitrate 45 mg/L, arsenic 0.01/0.05 mg/L, iron 1.0 mg/L, and no coliform in any 100 mL sample. Residual free chlorine minimum 0.2 mg/L (0.5 mg/L in areas of risk).
• Water-related disease classification: water-borne (cholera, typhoid, hepatitis A/E), water-washed/scarce (trachoma, scabies), water-based (schistosomiasis, guinea worm), water-related vector-borne (malaria, dengue, filariasis), and chemical (fluorosis, arsenicosis — endemic in parts of West Bengal, Bihar, Assam, UP; fluorosis in Rajasthan, Telangana, Gujarat).
• Purification: on a large scale — storage, coagulation–flocculation (alum), sedimentation, rapid/slow sand filtration, disinfection (chlorination to a free residual, contact 1 hour), optional ozonation/UV. Small scale — boiling (rolling boil), chlorine tablets (halazone), SODIS, candle/ceramic and membrane filters.
• Tests: presumptive coliform count/MPN, membrane filtration, H2S strip test, thermotolerant (faecal) coliform; chemical indicators — BOD5 at 20 °C, COD, dissolved oxygen, residual chlorine (orthotolidine/DPD).
• Sanitation: Swachh Bharat Mission (Grameen and Urban) — ODF, ODF+ and ODF++ protocols; sanitary latrine criteria (water seal, no fly/insect access, no contamination of soil/water/handling). Sewage treatment: preliminary (screening, grit), primary (sedimentation), secondary (activated sludge, trickling filter, UASB), tertiary (nutrient and pathogen removal). Effluent discharge standards are set under the Water (Prevention and Control of Pollution) Act, 1974 and the Environment (Protection) Rules, 1986.
• Solid and hazardous waste: the Solid Waste Management Rules, 2026 (in force 1 April 2026) replaced the 2016 Rules; biomedical, plastic, e-waste and hazardous waste rules are covered in the separate waste-management note — here only the health link matters: rag-picker injuries, dioxins from open burning, leachate contamination of groundwater, vector breeding in uncollected waste.
• Vector control: environmental (source reduction, filling, drainage, intermittent irrigation), chemical (indoor residual spray, larvicides, temephos, LLINs), and biological (Gambusia/guppy fish, Bti). Integrated vector management is the current approach, with insecticide-resistance monitoring.

Occupational hazards, diseases and industrial hygiene

• Classification of hazards: 1) Physical — heat, cold, noise, vibration, ionising and non-ionising radiation, pressure, poor illumination; 2) Chemical — dusts, fumes, gases, vapours, mists, solvents, metals; 3) Biological — brucellosis, leptospirosis, anthrax, tetanus, TB, hepatitis B/C and HIV via needle-stick; 4) Mechanical — machinery injuries, about 10% of workplace accidents; 5) Ergonomic — manual handling, repetitive strain, awkward posture; 6) Psychosocial — stress, shift work, burnout, violence.
• Pneumoconioses (dust-induced fibrotic lung disease), caused by respirable dust mostly 0.5–5 µm: silicosis (free crystalline silica — stone crushing, quarrying, foundry, slate pencil, agate grinding; raises TB risk sharply — silicotuberculosis); coal workers' pneumoconiosis (anthracosis, with progressive massive fibrosis); asbestosis (plus pleural plaques, mesothelioma, lung cancer); byssinosis (cotton/flax dust — Monday chest tightness, "Monday fever"); bagassosis (sugarcane bagasse, a hypersensitivity pneumonitis); farmer's lung (mouldy hay, thermophilic actinomycetes); siderosis, stannosis, baritosis (mostly benign).
• Chemical poisoning: lead (anaemia with basophilic stippling, punctate basophilia, blue line on gums, wrist drop, colic, encephalopathy in children); mercury (erethism, tremor, gingivitis); arsenic; cadmium (itai-itai, renal tubular damage, emphysema); manganese (parkinsonism); benzene (aplastic anaemia, leukaemia); organophosphates (cholinesterase inhibition); carbon monoxide; methyl isocyanate (Bhopal, 1984 — the defining Indian industrial disaster and the origin of much of India's chemical safety law).
• Physical agents: noise-induced hearing loss — permanent sensorineural loss beginning with a 4 kHz notch on audiometry; legal workplace limit in India 90 dB(A) for 8 hours with a 5 dB exchange rule and a 115 dB(A) ceiling, impulse noise not above 140 dB peak. Heat disorders — heat cramps, heat exhaustion, heat syncope, heat stroke, prickly heat; prevention by acclimatisation, hydration, work–rest cycles, shaded rest. Vibration — hand-arm vibration syndrome/Raynaud's phenomenon of occupational origin, whole-body vibration and low back pain. Radiation — AERB regulates ionising radiation, personnel monitoring by TLD badges and dose limit 20 mSv/year averaged over 5 consecutive years (not exceeding 30 mSv in any single year) for radiation workers.
• Occupational cancers: scrotal cancer (mineral oil/soot), bladder cancer (aromatic amines, benzidine), angiosarcoma of liver (vinyl chloride), nasal and sinus cancer (wood/chrome/nickel dust), leukaemia (benzene, radiation), mesothelioma (asbestos).
• Hierarchy of controls (most to least effective): elimination → substitution → engineering controls (enclosure, local exhaust ventilation, wet methods, isolation) → administrative controls (job rotation, limiting exposure time, training) → personal protective equipment (last resort: respirators, earplugs/muffs, gloves, goggles, safety shoes, aprons).
• Occupational health services: pre-placement examination, periodic medical examination, notification of occupational disease, first aid and OHC, ambulance room, canteen and crèche provisions, health education, and medical and health records retained per statute. Fitness-to-work and rehabilitation/placement of the disabled worker.
• Agencies: DGFASLI (Directorate General Factory Advice Service and Labour Institutes) with CLI/RLIs; NIOH (ICMR National Institute of Occupational Health, Ahmedabad); state factory inspectorates; ESIC hospitals and the Occupational Disease Centre; CPCB/SPCBs for environmental compliance; CAQM for NCR air.

Indian legal and institutional framework

• Occupational Safety, Health and Working Conditions Code, 2020, in force from 21 November 2025, subsumed and replaced the Factories Act, 1948, the Mines Act, 1952, the Dock Workers (Safety, Health and Welfare) Act, 1986, the BOCW Act, 1996, the Contract Labour Act, the Inter-State Migrant Workmen Act, the Plantations Labour Act and others — a single code covering registration of establishments, duties of employers, annual free health examination, appointment letters, welfare facilities, hazardous-process provisions, notification of accidents and occupational diseases, and a National/State Occupational Safety and Health Advisory Board. Hazardous processes, permissible exposure limits of chemicals and notifiable diseases are carried in the Code's Schedules and central rules; where a numerical limit matters, it should be read from the current rules rather than recalled from the former Factories Act schedules.
• The other three codes in force from the same date: Code on Wages, 2019; Industrial Relations Code, 2020; Code on Social Security, 2020 (the last carries ESI and EPF, i.e. the medical benefit, disablement benefit and dependants' benefit that compensate occupational injury and disease, replacing the Workmen's/Employees' Compensation Act and the ESI Act).
• Employees' State Insurance under the Social Security Code: cash and medical benefits for employment injury; notional extension of employment and the doctrine of "arising out of and in the course of employment" govern entitlement; occupational diseases listed in the Code's schedule are deemed employment injuries.
• Environmental statutes: Water Act 1974; Air Act 1981; Environment (Protection) Act, 1986 (the umbrella Act, source of the EP Rules 1986, EIA Notification 2006, noise rules, waste rules); Public Liability Insurance Act 1991; National Green Tribunal Act 2010; Biological Diversity Act 2002. Noise Pollution (Regulation and Control) Rules, 2000: ambient limits dB(A) Leq day/night — industrial 75/70, commercial 65/55, residential 55/45, silence zone 50/40.
• EIA Notification, 2006 (under the EP Act): Category A projects appraised centrally, Category B by SEIAA; stages — screening, scoping (ToR), public consultation, appraisal, clearance; Health Impact Assessment is increasingly embedded in EIA. Consent to Establish and Consent to Operate from the SPCB; industries graded Red/Orange/Green/White.
• Principles: polluter pays, precautionary principle, sustainable development, public trust doctrine, absolute liability (M.C. Mehta v. Union of India), and the right to a healthy environment read into Article 21; Articles 48A and 51A(g) are the Constitutional duties.
• Climate and health: heat action plans, NPCCHH, SDG targets 3.9 (deaths from pollution and chemicals), 6 (water and sanitation), 7 (clean energy), 11.6 (urban air quality) and 13.

Prevention, surveillance and measurement in practice

• Levels of prevention applied: primordial (fuel and land-use policy), primary (engineering control, immunisation of workers against hepatitis B/tetanus, safe water supply), secondary (periodic medical examination, audiometry, spirometry, chest X-ray ILO classification for pneumoconiosis, biological monitoring), tertiary (treatment, rehabilitation, compensation, redeployment).
• Surveillance: notification of occupational diseases by the certifying surgeon/medical officer; accident reporting with frequency and severity rates; environmental monitoring by CAAQMS (continuous ambient air quality monitoring stations) and NAMP (National Air Quality Monitoring Programme) for ambient air; NWMP for water.
• Instruments: high-volume and respirable dust samplers, gravimetric cyclone samplers, personal air sampling pumps with filters/sorbent tubes, Draeger/colorimetric tubes, sound level meter and noise dosimeter, WBGT meter, lux meter, anemometer for ventilation, Kata thermometer (classical comfort measure).
• Air pollution episodes studied in exams: Meuse Valley 1930, Donora 1948, London smog 1952, Bhopal 1984, Chernobyl 1986; Minamata (methyl mercury) and itai-itai (cadmium) for water pollution.
• Limitations of practice in India: large informal/unorganised sector (the great majority of the workforce) outside factory inspection; under-diagnosis and under-reporting of silicosis; few occupational health physicians; weak ambient monitoring density outside metros; fines and consents that are weaker deterrents than the cost of compliance.

Key points

• Environmental health - control of disease from air, water, soil, food, housing, radiation, noise and vectors; occupational health - the same plus ergonomic and psychosocial hazards of work.
• Risk = hazard × exposure - hazard is intrinsic, risk depends on concentration and duration, hence 8-hour time-weighted averages.
• NAAQS, 2009 - 12 pollutants; PM2.5 annual 40 and 24-hour 60 µg/m³; PM10 60 and 100 µg/m³; notified under the Air Act, 1981.
• AQI - six bands 0–500 on eight pollutants; the highest sub-index becomes the AQI, needing PM10 or PM2.5 plus two others.
• WHO AQG 2021 - PM2.5 annual 5 µg/m³; guidance only, far below Indian legal limits.
• IS 10500:2012 - drinking water standard; zero coliform per 100 mL, fluoride 1.0/1.5 mg/L, arsenic 0.01/0.05 mg/L, residual chlorine ≥0.2 mg/L.
• Pneumoconiosis - fibrosis from respirable dust 0.5–5 µm; silicosis (silica), asbestosis, byssinosis (cotton), bagassosis (sugarcane).
• Silicotuberculosis - silicosis greatly raises TB risk; mandates TB screening of stone-crusher and quarry workers.
• NIHL - sensorineural loss with a 4 kHz audiometric notch; Indian workplace limit 90 dB(A)/8 h, ceiling 115 dB(A).
• Hierarchy of controls - elimination, substitution, engineering, administrative, PPE; PPE is always the last resort.
• OSH&WC Code, 2020 - in force 21 November 2025; replaced the Factories, Mines, Dock Workers, BOCW, Contract Labour and Plantations Acts.
• Code on Social Security, 2020 - carries ESI and employment-injury compensation, replacing the Employees' Compensation and ESI Acts.
• Environment (Protection) Act, 1986 - umbrella Act; source of EP Rules, EIA Notification 2006, Noise Rules 2000 and the waste rules.
• Noise Rules, 2000 - day/night dB(A) Leq: industrial 75/70, commercial 65/55, residential 55/45, silence zone 50/40.
• NCAP, 2019 - particulate reduction in non-attainment cities; GRAP and CAQM for Delhi-NCR; NPCCHH for climate-sensitive illness.
• Healthy-worker effect - exposed workforces are fitter than the general population, biasing occupational mortality studies downwards.
• Key institutions - CPCB/SPCB, CAQM, DGFASLI, NIOH Ahmedabad, AERB, ESIC, NGT.
• Biological monitoring - blood lead, urinary hippuric acid (toluene), serum cholinesterase (organophosphates); measures internal dose, not air concentration.

Formulas and examples

Example 1 — 8-hour TWA against a limit. A worker in a paint shop is exposed to toluene: 2 hours at 120 ppm, 3 hours at 60 ppm, 2 hours at 30 ppm and 1 hour at 0 ppm (break).

• Σ(Ci × ti) = (2×120) + (3×60) + (2×30) + (1×0) = 240 + 180 + 60 + 0 = 480 ppm·h.
• TWA = 480/8 = 60 ppm.
• Against a TWA limit of 50 ppm for toluene (the value used in most Indian schedules — read the current rules for the notified figure), exposure exceeds the limit by 20%, so engineering control (local exhaust) plus respiratory protection is required.
• In mg/m³: toluene MW 92.14 → 60 × 92.14/24.45 ≈ 226 mg/m³.

Example 2 — noise dose and permitted time. A press operator spends 4 hours at 95 dB(A) and 3 hours at 90 dB(A).

• Permitted time at 95 dB(A): T = 8/2^(95−90)/5 = 8/2 = 4 h. At 90 dB(A): T = 8 h.
• Dose D = (4/4 + 3/8) × 100 = (1 + 0.375) × 100 = 137.5% — well above 100%, so the exposure is illegal as scheduled.
• Fix: reduce time at 95 dB(A) to 2 hours → D = (2/4 + 3/8) × 100 = 87.5%, acceptable; or enclose the press to cut the level.
• If two presses each produce 92 dB at the operator's position, combined Ltotal = 10 log10(2 × 10^9.2) = 92 + 3 = 95 dB.

Example 3 — AQI from PM2.5. A monitoring station in Kanpur records a 24-hour average PM2.5 of 148 µg/m³. The Indian AQI breakpoints for PM2.5 are 0–30 (0–50), 31–60 (51–100), 61–90 (101–200), 91–120 (201–300), 121–250 (301–400).

• 148 falls in the band 121–250 → index range 301–400.
• Ip = [(400 − 301)/(250 − 121)] × (148 − 121) + 301 = (99/129) × 27 + 301 = 0.7674 × 27 + 301 = 20.7 + 301 ≈ 322.
• AQI 322 = Very Poor category; if PM10 or NO2 gave a higher sub-index, that one would be reported instead. Compare with NAAQS: 148 µg/m³ is 2.5 times the 24-hour standard of 60 µg/m³.

Example 4 — accident frequency and severity. A textile mill employs 600 workers working 8 hours a day for 300 days; in one year there were 18 lost-time injuries and 540 man-days lost.

• Man-hours worked = 600 × 8 × 300 = 1,440,000.
• Frequency rate = 18 × 1,000,000/1,440,000 = 12.5 per million man-hours.
• Severity rate = 540 × 1,000,000/1,440,000 = 375 man-days lost per million man-hours.
• Average days lost per injury = 540/18 = 30 days; incidence rate = 18 × 1,000/600 = 30 per 1,000 workers.

Example 5 — attributable risk in a silica-exposed cohort. Chest-X-ray-confirmed silicosis is found in 90 of 600 stone-crusher workers and in 6 of 600 matched unexposed men.

• Ie = 90/600 = 0.15 (15%); Iu = 6/600 = 0.01 (1%). Relative risk = 0.15/0.01 = 15.
• Attributable risk (risk difference) = 0.15 − 0.01 = 0.14 → 14 cases per 100 exposed workers are attributable to the dust.
• AR% in the exposed = (0.14/0.15) × 100 = 93.3% — almost all disease in the exposed group is occupational.
• If 4% of the district's male workforce is so exposed, PAF = 0.04(15 − 1)/[0.04(15 − 1) + 1] = 0.56/1.56 = 35.9% of silicosis in the population.

Where it is used

• EHS/HSE roles in manufacturing: Tata Steel, Reliance, L&T, Hindustan Unilever, Asian Paints, Maruti — exposure monitoring, hierarchy-of-controls design, safety audits, incident rate reporting, ISO 45001 and ISO 14001 systems.
• Pollution control boards and consultancies: CPCB/SPCB monitoring and consent management, EIA and environmental monitoring consultants, CAAQMS network operation, air-quality data analysis for NCAP city action plans.
• Occupational health services and ESIC: pre-placement and periodic medical examinations, audiometry and spirometry camps, occupational disease certification, NIOH and DGFASLI institutes, mines and dock health services under the OSH&WC Code.
• Municipal and district public health: water quality surveillance and chlorination checks, sanitary surveys, vector control under NVBDCP/NCVBDC, heat action plans, outbreak investigation of water-borne disease.
• Real Indian examples: Rajasthan's silicosis grant and pneumoconiosis policy for mine and sandstone workers; the Delhi-NCR GRAP and stubble-burning season; arsenic mitigation in West Bengal and fluorosis control in Rajasthan; the Bhopal gas tragedy and its continuing health surveillance.
• ESG, sustainability and development sector: BRSR reporting on emissions, water and safety metrics; WHO/UNICEF, PATH, Vital Strategies, CSE and NGO work on clean air, clean cooking and WASH.

Interview questions

• Q: What is the difference between a hazard and a risk? A: A hazard is the inherent capacity of an agent to cause harm; risk is the probability and severity of harm actually occurring, which depends on exposure concentration and duration.
• Q: State the hierarchy of controls and why PPE comes last. A: Elimination, substitution, engineering controls, administrative controls, then PPE. PPE protects only the individual wearer, depends on correct fit and discipline, and fails silently, whereas engineering controls remove the hazard for everyone.
• Q: How is the Indian AQI computed and reported? A: Sub-indices are calculated for up to eight pollutants by linear interpolation between breakpoints; the highest sub-index becomes the AQI, provided data for at least three pollutants including PM10 or PM2.5 are available.
• Q: Which law now governs factory and mine worker safety in India? A: The Occupational Safety, Health and Working Conditions Code, 2020, in force from 21 November 2025, which replaced the Factories Act, 1948, the Mines Act, 1952, the Dock Workers Act and the BOCW Act, among others.
• Q: Why do silicosis patients so often get tuberculosis? A: Silica particles impair alveolar macrophage function and cause fibrosis, so mycobacterial clearance fails; silicotuberculosis is common enough that TB screening is part of silicosis surveillance.
• Q: A worker has a notch at 4 kHz on audiometry. What do you suspect and what do you do? A: Early noise-induced hearing loss. Measure the noise level, check the dose against 90 dB(A)/8 h, apply engineering control and hearing protection, and repeat audiometry; the existing loss is permanent.
• Q: What is the healthy-worker effect? A: Employed people are on average healthier than the general population, so comparing worker mortality with general population mortality underestimates occupational risk; an internal comparison group is preferable.
• Q: Difference between a permissible exposure limit and a biological monitoring value? A: A PEL limits the concentration in workplace air; biological monitoring measures the agent or its metabolite in the body and so captures total dose from all routes, including skin absorption and poor PPE use.
• Q: Which agency enforces drinking water quality and what standard applies? A: Water supply is a state/municipal responsibility, with surveillance by the state public health department and Jal Jeevan Mission laboratories; the quality specification is IS 10500:2012, which requires no coliform in a 100 mL sample.
• Q: Is household air pollution still a major problem if LPG coverage is high? A: Yes — connections do not guarantee sustained refill use; stacking of LPG with biomass continues in poorer rural households, so exposure surveys, not connection counts, measure progress.
• Q: Why is PPE alone an unacceptable answer for silica dust in a stone-crushing unit? A: Respirators need fit testing, maintenance and continuous use in heat and dust, where compliance collapses; wet suppression, enclosure and local exhaust ventilation cut the dust at source for all workers including passers-by.
• Q: What are the main limitations of occupational health regulation in India? A: Most workers are in the unorganised sector outside inspection coverage, occupational diseases are heavily under-notified, trained occupational health professionals are few, and penalties are often lower than the cost of compliance.

Common mistakes

• Quoting WHO air quality guideline values as if they were India's legal NAAQS limits, or averaging sub-indices instead of taking the maximum when computing AQI.
• Citing the Factories Act, 1948 or the Mines Act, 1952 as current law — both were replaced by the OSH&WC Code, 2020 in force from 21 November 2025; they may be named only as the former law.
• Putting PPE first in control measures, or naming PPE as the only measure in a long-answer question.
• Confusing pneumoconioses: byssinosis is cotton dust, bagassosis is sugarcane bagasse, siderosis is iron — and assuming all dust diseases are fibrotic (siderosis and baritosis are largely benign).
• Mixing up the 5 dB and 3 dB noise exchange rules, or adding noise levels arithmetically instead of logarithmically (92 + 92 dB is 95 dB, not 184).
• Reporting an 8-hour TWA without including the unexposed hours of the shift in the denominator, which falsely raises the average.
• Confusing relative risk with attributable risk, and attributable risk in the exposed with the population attributable fraction.

Related topics

Waste management rules: plastic, e-waste and biomedical · Epidemiology: measures of association and study designs · Communicable disease control and vector-borne diseases · Health policy, legislation and regulation in India · Disaster management and emergency public health · Biostatistics and survey methods.