A 35-year-old farmer from rural Maharashtra presents with chronic exposure to pesticides. On examination, he has hyperpigmentation, hyperkeratosis of palms and soles, and Mees' lines on nails. Which is the most common route of arsenic poisoning in agricultural workers?

## Most Common Route of Arsenic Poisoning in Agricultural Workers **Key Point:** Ingestion of arsenic-contaminated groundwater is the most common route of chronic arsenic poisoning globally, including in agricultural workers in rural India. This is well-established in standard toxicology and forensic medicine texts (Reddy's Essentials of Forensic Medicine; Modi's Medical Jurisprudence). ### Routes of Arsenic Exposure | Route | Context | Frequency in Agriculture | |-------|---------|-------------------------| | **Ingestion (groundwater)** | Naturally occurring arsenic in groundwater; agricultural runoff | **Most common** | | Inhalation | Spray drift, dust during mixing/application | Less common; relevant in industrial smelting | | Dermal absorption | Direct contact with arsenic-containing solutions | Least efficient (low penetration) | | Occupational (smelting) | Industrial setting, not agricultural | Rare in farmers | ### Why Groundwater Ingestion Is the Primary Route 1. Arsenic occurs naturally in groundwater in many parts of India (West Bengal, Bihar, Uttar Pradesh, Maharashtra) due to geological leaching 2. Agricultural runoff and pesticide use further contaminate local water sources 3. Rural farmers rely heavily on groundwater (wells, borewells) for drinking — providing chronic daily exposure 4. Gastrointestinal absorption of inorganic arsenic from water is highly efficient (~90%) 5. Chronic low-level ingestion over months to years produces the classic triad: **Mees' lines, hyperpigmentation, and hyperkeratosis** ### Mechanism of Chronic Arsenic Toxicity via Ingestion - Inorganic arsenic (As³⁺ / As⁵⁺) is absorbed rapidly from the GI tract - Distributed to liver, kidneys, skin, nails, and hair - Inhibits pyruvate dehydrogenase and other sulfhydryl-dependent enzymes - Chronic accumulation → keratosis, pigmentation changes, peripheral neuropathy, and Mees' lines (transverse white bands on nails) **Clinical Pearl:** Mees' lines, hyperpigmentation, and palmoplantar hyperkeratosis are the hallmark triad of **chronic arsenic poisoning** and are most commonly seen in populations with prolonged groundwater exposure, not acute inhalation. **High-Yield:** The WHO and ICMR recognize groundwater contamination as the single largest source of chronic arsenic exposure in South Asian agricultural communities. Inhalation is the dominant route in **smelting/mining industries**, not in farming. **Warning:** Do NOT confuse occupational inhalation (relevant in smelting/mining) with the most common route in agricultural workers. The stem describes a farmer with chronic exposure — groundwater ingestion is the answer. ### Why Inhalation Is NOT the Most Common Route in Farmers - Arsenic-based pesticides (e.g., lead arsenate) have been largely banned in India - Even when used, inhalation exposure is intermittent and lower in magnitude than daily water consumption - Respiratory absorption is significant only in enclosed industrial environments (smelters, mines) - Dermal absorption through intact skin is minimal (<5% of total exposure)