10.3 Environmental & Nutritional Pathology: Air Pollution, Tobacco, Metals, Occupational Lung Disease & Deficiency States
Key Takeaways
Indoor smoke from wood and charcoal cooking fires causes COPD, acute respiratory infections in children and lung cancer; carbon monoxide from generators and stoves causes hypoxic injury with a cherry-red color.
Lead causes microcytic anemia with basophilic stippling, peripheral neuropathy (wrist drop), encephalopathy in children and lead lines; mercury causes neurologic damage and tremor (Minamata disease); arsenic causes hyperkeratosis, Mees lines and skin, lung and bladder cancer.
Silicosis affects upper lobes with eggshell hilar node calcification and raises tuberculosis risk; asbestosis affects lower lobes with ferruginous bodies, pleural plaques, lung carcinoma and mesothelioma.
Kwashiorkor (protein deficit) causes edema, fatty liver and flaky-paint dermatosis with relatively preserved fat stores; marasmus (calorie deficit) causes severe wasting without edema.
Vitamin A deficiency causes night blindness, Bitot spots and squamous metaplasia; thiamine deficiency causes beriberi and Wernicke encephalopathy; vitamin C deficiency causes scurvy from defective collagen hydroxylation.
Why this area matters
The TOS lists "environmental toxicants (outdoor and indoor air pollution, metals as environmental pollutants); nutritional deficiencies (dietary insufficiency, vitamin deficiency)". These topics reappear in Preventive Medicine (occupational and environmental health), Pediatrics (malnutrition) and Medicine (COPD, neuropathy). Learn the exposure, the mechanism and the hallmark lesion.
Air pollution
Outdoor pollutants include:
- particulate matter (PM2.5 and PM10 from vehicles, industry and burning), which causes airway inflammation, cardiovascular events and lung cancer;
- ozone, which forms smog and irritates the airways;
- sulfur dioxide and nitrogen dioxide, which worsen asthma;
- carbon monoxide.
Urban traffic and open burning are major sources in Philippine cities.
Indoor pollutants:
- Biomass and charcoal smoke from cooking in poorly ventilated homes causes chronic bronchitis and COPD (especially in women), pneumonia in children and lung cancer.
- Tobacco smoke, including second-hand smoke.
- Carbon monoxide from generators, kerosene heaters and stoves in enclosed spaces. CO binds hemoglobin about 200 to 250 times more avidly than oxygen and shifts the dissociation curve left. The result is hypoxic injury to the brain (globus pallidus) and heart, cherry-red skin and livor, and falsely normal pulse oximetry.
- Radon, molds and allergens such as dust mites.
Tobacco
Tobacco smoke contains more than 60 carcinogens, including polycyclic hydrocarbons and nitrosamines. Its effects include:
- lung cancer (squamous cell and small cell more than adenocarcinoma);
- cancers of the oral cavity, larynx, esophagus, bladder, pancreas, kidney and cervix;
- atherosclerosis and myocardial infarction;
- COPD;
- peptic ulcer;
- in pregnancy, low birth weight.
Smoking cessation steadily reduces these risks.
Metals as environmental pollutants
| Metal | Sources | Main lesions |
|---|---|---|
| Lead | Old paint, battery recycling, contaminated soil, some cosmetics and traditional remedies | Blocks heme synthesis (ALA dehydratase, ferrochelatase), causing microcytic anemia with basophilic stippling; peripheral neuropathy (wrist and foot drop); encephalopathy and cognitive impairment in children; Burton gum lines; dense metaphyseal bands on X-ray; renal tubular injury |
| Mercury | Small-scale gold mining (amalgamation), contaminated fish (methylmercury), dental amalgam | Neurotoxicity (tremor, erethism, ataxia, visual-field constriction); Minamata disease from methylmercury; fetal brain damage; renal injury from inorganic mercury |
| Arsenic | Contaminated groundwater, pesticides, mining | Gastroenteritis (acute); chronically, hyperkeratosis and hyperpigmentation, Mees lines on nails, neuropathy, and skin, lung and bladder cancer; deposits in hair and nails |
| Cadmium | Batteries, smelting, contaminated rice | Renal tubular damage, osteomalacia (itai-itai disease), emphysema |
Occupational lung disease (pneumoconioses)
| Disease | Exposure | Pathology |
|---|---|---|
| Coal workers' pneumoconiosis | Coal dust | Anthracosis, coal macules and nodules; progressive massive fibrosis |
| Silicosis | Mining, quarrying, sandblasting, stone cutting | Whorled silicotic nodules, mostly in the upper lobes; eggshell calcification of hilar nodes; increased tuberculosis risk because silica damages macrophages |
| Asbestosis | Shipbuilding, insulation, roofing, brake linings | Interstitial fibrosis of the lower lobes, ferruginous (asbestos) bodies, pleural plaques. Higher risk of lung carcinoma, which is greatest with smoking, and malignant mesothelioma |
| Hypersensitivity pneumonitis | Organic dusts (bird droppings, moldy hay, sugarcane bagasse: bagassosis) | Poorly formed granulomas; type III and IV reactions |
Physical agents (overview)
- Thermal injury: burns and heat stroke. In heat stroke, temperature above 40°C with CNS dysfunction leads to rhabdomyolysis and DIC.
- Electrical injury and lightning: covered in Legal Medicine.
- Ionizing radiation: most damaging to dividing cells (marrow, gonads, gut epithelium). It causes acute radiation syndrome, fibrosis, and later leukemia and thyroid cancer.
Nutritional pathology
Protein-energy malnutrition
| Feature | Marasmus | Kwashiorkor |
|---|---|---|
| Main deficit | Total calories | Protein, relative to calories |
| Weight for height | Severe wasting; "skin and bones" | Less wasting, masked by edema |
| Subcutaneous fat and muscle | Markedly depleted | Relatively preserved fat |
| Serum albumin | Near normal | Low, causing edema |
| Liver | Not fatty | Fatty liver from impaired lipoprotein export |
| Skin and hair | Wrinkled skin | "Flaky paint" dermatosis, depigmented, sparse hair (flag sign) |
Both conditions cause thymic atrophy and immune deficiency, and children die of infections such as measles, diarrhea and pneumonia.
Vitamin and mineral deficiencies
| Deficiency | Pathology and clinical lesion |
|---|---|
| Vitamin A | Night blindness, xerophthalmia, Bitot spots, keratomalacia (blindness); squamous metaplasia of respiratory and urinary epithelium; severe measles |
| Vitamin D | Rickets in children (craniotabes, rachitic rosary, bowed legs) and osteomalacia in adults: defective mineralization of osteoid |
| Vitamin C | Scurvy: defective hydroxylation of proline and lysine in collagen, causing perifollicular hemorrhage, bleeding gums, subperiosteal hemorrhage and poor wound healing |
| Thiamine (B1) | Dry beriberi (neuropathy), wet beriberi (high-output heart failure), infantile beriberi in breastfed infants of deficient mothers, Wernicke encephalopathy (confusion, ophthalmoplegia, ataxia) in alcoholics |
| Niacin (B3) | Pellagra: dermatitis, diarrhea, dementia (and death); seen with maize diets and in carcinoid syndrome |
| Folate and B12 | Megaloblastic anemia; B12 deficiency also causes subacute combined degeneration of the spinal cord |
| Vitamin K | Bleeding; hemorrhagic disease of the newborn if vitamin K is not given at birth |
| Iodine | Goiter, hypothyroidism, cretinism. The ASIN law (RA 8172) requires iodization of food-grade salt; RA 11985 (2024) made iodization optional for artisanal, non-food-grade and export salt |
| Iron | Microcytic hypochromic anemia, koilonychia, pica; common in Filipino children and pregnant women |
| Zinc | Growth failure, acrodermatitis enteropathica, poor wound healing, diarrhea |
Obesity is the opposite problem. It is linked to insulin resistance, type 2 diabetes, hypertension, fatty liver disease, osteoarthritis, sleep apnea, and cancers of the endometrium, breast and colon.
A 4-year-old boy living near an informal battery-recycling site has abdominal colic, irritability and anemia. His blood smear shows microcytic red cells with coarse basophilic stippling. Which toxin is most likely?
Arsenic
Cadmium
Mercury
Lead
A 60-year-old retired shipyard worker who also smoked has dyspnea, bilateral lower-lobe interstitial fibrosis and calcified pleural plaques. Sputum shows golden-brown beaded rods that stain with Prussian blue. What is his greatest cancer risk?
Malignant mesothelioma, which is far more common than lung cancer in asbestos workers
Hepatic angiosarcoma
Bronchogenic carcinoma, with a risk multiplied by smoking
Nasopharyngeal carcinoma
A 2-year-old from a poor household eats mainly rice porridge. She has generalized edema, an enlarged liver, peeling "flaky paint" skin lesions and sparse, light-colored hair. Serum albumin is low. Which condition is present, and why is the liver enlarged?
Rickets; vitamin D deficiency causes hepatic osteomalacia
Kwashiorkor; protein deficiency impairs apolipoprotein synthesis, causing fatty liver
Marasmus; the total calorie deficit causes excess glycogen and fat storage in the liver cells
Scurvy; vitamin C deficiency causes hepatic hemorrhage
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