CHAPTER 2-16: ANTIMONY AND STIBINE

INTRODUCTION

Antimony (Sb) is a versatile trace element widely used for hardening soft metal alloys; for compounding rubber; as a major flame retardant component (5–20%) in plastics, textiles, and clothing; and as a coloring agent in dyes, varnishes, paints, and glazes. Exposure to antimony dusts and fumes may occur during mining and refining of ores, in glassworking, and from the discharge of firearms. Organic pentavalent antimony compounds (sodium stibogluconate and antimoniate meglumine) are commonly used worldwide as antiparasitic drugs. Foreign or folk remedies may contain antimony potassium tartrate ("tartar emetic" or trivalent antimony), which was widely used in previous centuries as an emetic, purgative, and aversive therapy for alcohol abuse. Stibine (antimony hydride, SbH3) is a colorless gas with the odor of rotten eggs that is produced as a by-product when antimony-containing ore or furnace slag is treated with acid.

MECHANISM OF TOXICITY

The mechanism of antimony and stibine toxicity is not known. Because these compounds are chemically related to arsenic and arsine gas, respectively, their modes of action may be similar.

1. Antimony compounds probably act by binding to sulfhydryl groups, enhancing oxidative stress, and inactivating key enzymes. Ingested antimonials are corrosive to GI mucosal membranes and demonstrate significant enterohepatic recirculation.

2. Stibine, like arsine, may cause hemolysis. It is also an irritant gas.

TOXIC DOSE

1. An estimated toxic amount of the organic antimony compound tartar emetic (nonelemental antimony) is 0.1–1 g. The lethal oral dose of metallic antimony in rats is 100 mg/kg of body weight; the trivalent and pentavalent oxides are less toxic, with LD50 in rats ranging from 3,200 to 4,000 mg/kg of body weight. The recommended workplace limit (ACGIH TLV-TWA) for antimony is 0.5 mg/m³ as an 8-hour time-weighted average. The air level considered to be immediately dangerous to life or health (IDLH) is 50 mg/m³.

2. The recommended workplace limit (ACGIH TLV-TWA) for stibine is 0.1 ppm as an 8-hour time-weighted average. The air level considered immediately dangerous to life or health (IDLH) is 5 ppm.

CLINICAL PRESENTATION

1. Acute ingestion of antimony causes nausea, vomiting, hemorrhagic gastritis, and diarrhea. Hepatitis, renal insufficiency, and prolongation of the QTc interval may occur. Cardiac dysrhythmias (including torsade de pointes), hyperkalemia, pancreatitis, aplastic crisis, and arthralgias have been associated with the use of antimonial antiprotozoal drugs, such as stibogluconate, for the treatment of parasitic infections.

2. Acute stibine gas inhalation causes acute hemolysis, resulting in anemia, jaundice, hemoglobinuria, and renal failure.

3. Chronic exposure to antimony dusts and fumes in the workplace is the most common type of exposure and may result in headache, anorexia, respiratory tract and eye irritation, pneumonitis/pneumoconiosis, peptic ulcers, and dermatitis ("antimony spots"). Sudden death presumably resulting from a direct cardiotoxic effect has been reported in workers exposed to antimony trisulfide. Based on evidence of in vitro genotoxicity and limited rodent ...