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Background: Mercury is a naturally occurring heavy metal that finds wide application in industrial and household settings. It exists in three chemical forms which include elemental (Hg0 ), inorganic mercurous (Hg+) or mercuric (Hg++) salts, and organic compounds. All forms are highly toxic, particularly to the nervous, gastrointestinal, and renal systems. Common circumstances of exposure include recreational substance use, suicide or homicide attempts, occupational hazards, traditional medicines, and endemic food ingestions as witnessed in the public health disasters in Minamata Bay, Japan and in Iraq. Poisoning can result in death or long-term disabilities. Clinical manifestations vary with chemical form, dose, rate, and route of exposure. Aims and objectives: To summarize the incidence of mercury poisoning encountered at an Indian Poison Center and use three cases to highlight the marked variations observed in clinical manifestations and long-term outcomes among poisoned patients based on differences in chemical forms and routes of exposure to mercury. Materials and methods: A structured retrospective review of the enquiry-database of the Poison Information Center and medical records of patients admitted between August 2019 and August 2021 in a tertiary care referral center was performed. All patients with reported exposure to mercury were identified. We analyzed clinical data and laboratory investigations which included heavy metal (arsenic, mercury, and lead) estimation in whole blood and urine samples. Additionally, selected patients were screened for serum voltage-gated potassium ion channels (VGKC)— contactin-associated protein-like 2 (CASPR2) antibodies. Three cases with a classical presentation were selected for detailed case description. Results: Twenty-two cases were identified between August 2019 and August 2021. Twenty (91%) were acute exposures while two (9%) were chronic. Of these, three representative cases have been discussed in detail. Case 1 is a 3.5-year-old girl who was brought to the emergency department with suspected elemental-mercury ingestion after biting a thermometer. Clinical examination was unremarkable. Chest and abdominal radiography revealed radiodense material in the stomach. Subsequent serial radiographs documented distal intestinal transit of the radiodense material. The child remained asymptomatic. This case exemplifies the largely nontoxic nature of elemental mercury ingestion as it is usually not absorbed from the gastrointestinal tract. Case 2 is a 27-year-old lady who presented with multiple linear nodules over both upper limbs after receiving a red intravenous injection for anemia. Imaging revealed metallic-density deposits in viscera and bones. Nodular biopsy was suggestive of mercury granulomas. A 24-hour urine mercury levels were elevated. She was advised chelation therapy with oral dimercaptosuccinic acid (DMSA). Case 3 is a 22-year-old lady who presented with acrodynia, neuromyotonia, tremulousness, postural giddiness, tachycardia, and hypertension for 2 months, associated with intractable, diffuse burning pain over the buttocks and both lower limbs, 1 month after completing a 3-week course of traditional medications for polycystic ovarian syndrome. A 24-hour urine normetanephrine levels and mercury levels were markedly elevated. Serum anti-VGKC antibodies were present. She was treated with glucocorticoids and oral DMSA with a favorable clinical response. Conclusions: The clinical manifestations of mercury toxicity are highly variable depending on the source, form, and route of mercury exposure and are related to its toxicokinetics.

Introduction: Service sector in Indian industrial growth has obtained significant numbers. Automobile service industry is one of the largest in the world with a majority of the workers in unorganized sector of the industry. This study was carried out among auto service industry workers in Vellore urban area to assess possible occupation related morbidity. Materials and Methods: A cross-sectional observation study was carried out among 106 automobile repair shop workers. Results: Half (47%) suffered work related stress, 32 (30.2%) reported exposure to dust, 81 (76%) to heat, and 50 (17%) to hazardous chemicals and heavy metals. More than 90% reported over exposure to petroleum products. A third reported cough for more than 2 weeks, more than a quarter reported gastrointestinal symptoms associated with work. Half of them reported musculoskeletal complaints associated with work with a quarter reporting un-intentional work place injuries. A tenth of them were found to have reduced pulmonary function on testing and nearly half had impaired sensory functions in peripheries. Reduced pulmonary function was found to be significantly associated with heavy metal exposure (P = 0.001). Peripheral neuropathy was significantly associated with years of occupation (P = 0.001), exposure to petroleum products (P = 0.03) and exposure to heavy metals (P = 0.018). Discussion: Half of the workers were unaware of health problems associated with their occupational exposures and thereby the use of personal protection is abysmally low. A very high proportion of workers had symptoms of cough, breathlessness, abdominal pain, abdominal discomfort and muscle aches. Almost a quarter of the workers had un-intentional occupational injuries in the last 6 months. Though they work in a high-risk environment with chances of fire hazard, falls and chemical exposures, none of the workshops had fire-extinguishers, first aid kits or any such safety devices.