A 35-year-old farmer from rural Punjab presents with chronic exposure to pesticides. On examination, he has hyperpigmentation of skin, 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:** In agricultural workers in rural Punjab (and similar endemic regions), **ingestion of arsenic-contaminated groundwater** is the most common route of chronic arsenic poisoning — not inhalation. ### Epidemiology of Arsenic Exposure Routes | Route | Frequency | Context | Absorption | | --- | --- | --- | --- | | **Ingestion (groundwater)** | **Most common (overall & agricultural)** | Contaminated tube wells, endemic regions | Via GI tract | | Inhalation | Occupational (smelters, miners) | Active pesticide spraying, dust | Rapid via alveoli | | Dermal | Least common | Minimal percutaneous absorption | Very slow | | Ingestion (food) | Variable | Bioaccumulation in crops | Moderate | **High-Yield:** Punjab, West Bengal, Bangladesh, and parts of Uttar Pradesh have well-documented arsenic contamination of groundwater from geological leaching. Agricultural workers in these regions drink from tube wells and hand pumps, making **ingestion of contaminated groundwater the predominant route** of chronic arsenic poisoning — as established by the WHO and ICMR. ### Clinical Features Consistent with Chronic Arsenic Poisoning The patient's presentation includes: - **Hyperpigmentation** (diffuse or raindrop "melanosis" pattern) - **Hyperkeratosis** of palms and soles (arsenical keratosis) - **Mees' lines** on nails (transverse white bands, highly suggestive in context) - **Chronic exposure** over months to years — consistent with groundwater ingestion **Clinical Pearl (Park's Textbook of Preventive & Social Medicine):** Chronic arsenicosis in South Asia is overwhelmingly driven by consumption of arsenic-rich groundwater (>10 µg/L WHO limit). The triad of melanosis, keratosis, and Mees' lines is the hallmark of chronic ingestion-route poisoning. ### Why Ingestion of Contaminated Groundwater is the Correct Answer 1. **Endemic region**: Punjab is a known arsenic-affected state in India; groundwater arsenic levels frequently exceed safe limits due to alluvial aquifer contamination. 2. **Chronic exposure pattern**: The clinical triad (hyperpigmentation, hyperkeratosis, Mees' lines) reflects months-to-years of low-dose ingestion, not acute inhalation. 3. **Population-level evidence**: ICMR and WHO data confirm groundwater ingestion as the #1 route in agricultural communities in this belt. 4. **Inhalation is primary in smelters/miners**: Occupational inhalation is the dominant route in metal smelting and mining industries — NOT in farmers using pesticides, where exposure is intermittent and dermal/inhalation doses are low. ### Distinction from Occupational Inhalation Route Inhalation is the primary route in: - Copper/gold smelter workers - Pesticide manufacturing plant workers - Miners handling arsenopyrite ores In contrast, **farmers** in endemic regions are primarily exposed via **drinking water** from contaminated aquifers, making ingestion the correct answer here. **Reference:** Park's Textbook of Preventive & Social Medicine, 26th ed.; WHO Arsenic Fact Sheet; Casarett & Doull's Toxicology.