Section 1 - CHEMICAL PRODUCT AND COMPANY IDENTIFICATION

PRODUCT NAME

HEXABORANE(10)

NFPA

PRODUCT USE

The unstable form of pentaborane. Intermediate.

SYNONYMS

B6-H10, "borane, hexa-", "hexaboron decahydride", borohexane

Section 2 - HAZARDS IDENTIFICATION

CANADIAN WHMIS SYMBOLS

EMERGENCY OVERVIEW

RISK

Spontaneously flammable in air.
May cause fire.

POTENTIAL HEALTH EFFECTS

ACUTE HEALTH EFFECTS

SWALLOWED

  Although ingestion is not thought to produce harmful effects, the material may still be damaging to the health of the individual following ingestion, especially where pre-  existing organ (e.g. liver, kidney) damage is evident. Present definitions of harmful or toxic substances are generally based on doses producing mortality (death) rather than those producing morbidity (disease, ill-health). Gastrointestinal tract discomfort may produce nausea and vomiting. In an occupational setting however, ingestion of insignificant quantities is not thought to be cause for concern.  Borate poisoning causes nausea, vomiting, diarrhea and pain in the upper abdomen. Often persistent vomiting occurs, and there may be blood in the feces. There may also be weakness, lethargy, headache, restlessness, tremors and convulsions. All borates cause similar effects; the lethal dose is over 30 grams. Poisoning initially stimulates the central nervous system before causing depression, as well as disturbing the digestive system, causing skin eruptions, and damage to the liver and kidneys. Borate is mostly eliminated from the body via the kidneys.  

EYE

  Although the material is not thought to be an irritant, direct contact with the eye may produce transient discomfort characterized by tearing or conjunctival redness (as with windburn).  

SKIN

  The material is not thought to produce adverse health effects or skin irritation following contact (as classified using animal models). Nevertheless, good hygiene practice requires that exposure be kept to a minimum and that suitable gloves be used in an occupational setting.  Open cuts, abraded or irritated skin should not be exposed to this material.  The material may accentuate any pre-existing skin condition.  Toxic effects may result from skin absorption.  

INHALED

  Inhalation may produce serious health damage*.  The material is not thought to produce respiratory irritation (as classified using animal models). Nevertheless inhalation of the material, especially for prolonged periods, may produce respiratory discomfort and occasionally, distress.  Inhalation of vapor may aggravate a pre-existing respiratory condition.  Inhalation toxicity of the inorganic boranes has been described extensively. Generally, central nervous system and respiratory effects are prominent. Accidental exposure of workers to pentaborane(9), has produced signs and symptoms consistent with central nervous system intoxication. Exposure to congeners of pentaborane is thought to produce similar effects. Tremors and convulsions have been reported following sufficiently large exposures to pentaborane(9). Lower concentrations have produced behavioural changes including loss of recent memory and may cause poor judgement to occur. Toxic signs in animals, in order of onset, were tremor, ataxia, convulsions and deaths, all deaths occurring within 24-hours of exposure. In dogs severe signs of toxicity were still observed at levels approximately one-half of the LC50 value though these were minimal; no signs were apparent at one-quarter LC50. A striking feature of animal experiments has been the high death rate whereas amongst exposed workers and even hospitalised workers, several have died or were left permanently disabled. Species differences appear to reside in metabolic differences in man and rodents. Symptoms of acute decaborane exposure include loss of coordination, convulsions, weakness, tremor, hyperexcitability, and narcosis. Toxic effects are also produced in the liver and kidney. Several of the CNS effects recorded in animals (incoordination, tremor and convulsive seizures) are seen in decaborane-exposed plant operators. Onset of symptoms may be delayed (24-48 hours) with mild exposures producing headache, dizziness and nausea; more severe exposures produce muscle spasm (which regresses within 24 hours). Dizziness and fatigue may persist for up to three days. Rabbits exposed to decaborane, for up to 6 hours at 56 ppm, died from effects that included convulsive seizures. Diborane produces toxic bronchopulmonary effects. Overexposure by humans, to diborane, produces a sensation of chest-tightness leading to diaphragmatic pain, shortness of breath, cough and occasionally, nausea. Nervous system intoxication may also occur. Respiratory distress in dogs and rabbits is followed by a slight fall in blood pressure, increased activity of the intestinal smooth muscle and an increase and subsequent diminution of cortical activity. These findings are consistent with anoxia (oxygen starvation). The primary effect of diborane poisoning is the production of pulmonary oedema which is the result of local irritation. This, in turn,  is produced by an exothermic hydrolysis reaction which results in the diborane decomposing into other toxic species. Other inorganic boranes are expected to produce similar effects. Pneumonitis is often encountered in human poisoning gas by diborane. Bradycardia occurs late in the intoxication, followed by ventricular fibrillation or the disappearance of ventricular activity, and death.  

CHRONIC HEALTH EFFECTS

  Principal routes of exposure are by accidental skin and eye contact and by inhalation of vapors especially at higher temperatures.  Borate can accumulate in the testes and deplete germ cells and cause withering of the testicles, according to animal testing. Hair loss, skin inflammation, stomach ulcer and anemia can all occur. Repeated swallowing or inhalation irritates the stomach, causes a loss of appetite, disturbed digestion, nausea and vomiting, red rash, dry skin and mucous membranes, reddening of the tongue, cracking of the lips, inflamed conjunctiva, swelling of the eyelids and kidney injury. Prolonged ingestion causes effects to the reproductive system in both males and females.  Rats exposed to pentaborane(9) for 5 hours/day, 5 days/week for up to 4 weeks at 3 ppm (calculated) exhibited hyperexcitability, tremors, and decreased body weight. Repeated exposures at 1 ppm for 4 weeks produced loss of body weight, diminished activity and amongst rabbits, ataxia. At 0.2 ppm monkeys were apathetic, anorexic and appeared anaesthetised. There was progressive incoordination, hindlimb immobility and muscle tremor in both nonhuman primates and dogs. Repeated exposure to decaborane by various routes produces toxic effects intermediate between the more toxic pentaborane and less toxic diborane. All routes of entry produce significant disability with skin absorption in rats and rabbits producing central nervous system effects more prominent than those produced by single exposures. Recovery from these effects may take several days (against a few hours for diborane). Daily inhalation exposures of 5-6 hours, for up to 6 months at 4.5 ppm, were fatal to rabbits after only a few exposures, dog and monkey (4-15 exposures), mice (10-100 exposures) and rats (135+ exposures). Performance decrements, in various types of operant behaviors, is apparent in monkeys following injection of 3-6 mg/kg. Workers exposed to decaborane may be expected to exhibit decline in tasks requiring continuous motor behaviour or a series of discriminations. Chronic effects of diborane exposure include respiratory distress. Prolonged exposure to low concentrations cause headache, vertigo, chills and sometimes, fever. Daily 6-hour exposures at 7 ppm proved fatal in dogs (10-25 exposures) and rats (7-113 exposures). Although pulmonary changes could not be substantiated, the repeated respiratory insult was thought to be the underlying cause of death. Dogs developed signs of respiratory infection, probably secondary to respiratory irritation resulting from hydrolysis of the molecule.