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CM3.1 | CM3.1 | Environmental Pollution Hazards — SDL Guide (Part 3)
Clinical Application: Recognising and Responding to Pollution-Related Illness
Clinical recognition of pollution-related disease requires a systematic occupational and environmental history as a mandatory component of the medical assessment. Key questions include: What is the patient's occupation? What substances are they exposed to at work? What is their home heating and cooking fuel? Where do they live relative to industrial sites, highways, or agricultural land? How long have they lived or worked there? Do symptoms worsen during pollution episodes (e.g. foggy/hazy days)? Do family members have similar symptoms?
Primary care interventions in a pollution context include: (a) individual counselling—advise high-risk patients (children, pregnant women, elderly, those with asthma/COPD/heart disease) to limit outdoor activity during poor AQI days, use N95 respirators when necessary, and avoid indoor combustion (switch to LPG or clean cooking fuels under PM Ujjwala Yojana); (b) clinical investigation—spirometry for suspected air-pollution-related lung disease; blood lead level for suspected lead exposure; urinary arsenic for those in endemic areas; audiometry for workers with occupational noise exposure; (c) reporting—notify the district health officer or IDSP unit for clusters of environment-linked disease.
A key advocacy role for physicians is supporting local air quality improvement: participating in NCAP consultations, advising panchayat/municipal bodies on clean cooking fuel schemes, and contributing data to environmental health surveillance. The doctor-as-public-health-advocate is an explicit NMC expectation.
CLINICAL PEARL
CO poisoning in winter is under-diagnosed in India. When a family group presents with headache, nausea, and confusion—especially in cold months when rooms are sealed—always consider CO poisoning from indoor combustion (coal/wood stoves, kerosene heaters, generators). The key clinical clue is that symptoms affect ALL occupants simultaneously and resolve on moving to fresh air. COHb on arterial blood gas is diagnostic; pulse oximetry is UNRELIABLE in CO poisoning because standard SpO2 cannot distinguish COHb from OHb. Treat immediately with 100% non-rebreather mask oxygen. In severe cases (COHb >25%, unconsciousness, pregnancy), hyperbaric oxygen (HBO) should be considered if available.
SELF-CHECK
A 34-year-old pregnant woman at 28 weeks presents with headache and nausea. Her SpO2 reads 98% on pulse oximetry. She was using a coal brazier for heating in a sealed room. Which investigation is MOST urgently needed and why?
A. Chest X-ray, as CO causes pneumonitis
B. Arterial blood gas with COHb measurement, because pulse oximetry cannot distinguish oxyhaemoglobin from carboxyhaemoglobin
C. Blood lead level, as coal combustion is the main source of lead poisoning
D. Urine for nitrate, to exclude methaemoglobinaemia
Reveal Answer
Answer: B. Arterial blood gas with COHb measurement, because pulse oximetry cannot distinguish oxyhaemoglobin from carboxyhaemoglobin
This is a classic CO poisoning scenario: winter, sealed room, indoor coal combustion, group symptoms. Pulse oximetry gives a falsely reassuring reading because the sensor wavelengths used cannot distinguish COHb from OHb—both absorb similarly at 660 nm. An arterial blood gas with co-oximetry is the correct diagnostic step. Pregnancy is a special concern because foetal haemoglobin has an even higher affinity for CO, and foetal exposure is disproportionately severe. Treatment is 100% oxygen; hyperbaric oxygen should be considered given the pregnancy.