Hydrogen sulfide respiratory toxicity

There is very little information on the toxicity of phosphorus pentasulfide. Irritancy of the respiratory tract would be expected because the substance is rapidly hydrolyzed to phosphoric acid and hydrogen sulfide pulmonary irritation is expected at concentrations of lOmg/m ... 

Hydrogen sulfide is a highly toxic and flammable gas. A 5-minute exposure to 1,000 ppm concentration in air can be fatal to humans (Patnaik, P. 1999. A Comprehensive Guide to the Hazardous Properties of Chemical Substances, 2nd ed. New York John Wiley). The symptoms are headache, nausea, nervousness, cough, eye irritation, and insomnia. High doses can produce unconsciousness and respiratory paralysis. 

Nonmetallic neurotoxins are frequently used in industry in manufacturing of chemicals and resins or as solvents. Some examples are hydrogen sulfide (which paralyzes specifically the nervous centers that control respiratory movement), carbon disulfide, -hexane, methyl -butyl ketone, and acrylamide. Exposure to all of these substances may occur through inhalation of vapors. In addition, carbondisufide and acrylamide may enter the system by dermal absorption. -Hexane and methyl -butyl ketone are not toxic by themselves but are activated by cytochrome P-450 to the neurotoxic hexanedione (CH3COCH2CH2COCH3). 

Health and Safety Factors. Carbonyl sulfide is dangerously poisonous, more so because it is practically ododess when pure. It is lethal to rats at 2900 ppm. Studies show an LD5Q (rat, ip) of 22.5 mg/kg. The mechanism of toxic action appears to involve breakdown to hydrogen sulfide (36). It acts principally on the central nervous system with death resulting mainly from respiratory paralysis. Litde is known regarding the health effects of subacute or chronic exposure to carbonyl sulfide a 400- Jg/m3 max level has been suggested until more data are available (37). Carbon oxysulfide has a reported inhalation toxicity in mice LD5Q (mouse) = 2900 ppm (37). 

Among the many toxicants that cause convulsions are chlorinated hydrocarbons, amphetamines, lead, organophosphates, and strychnine. There are several levels of coma, the term used to describe a lowered level of consciousness. At level 0, the subject may be awakened and will respond to questions. At level 1, withdrawal from painful stimuli is observed and all reflexes function. A subject at level 2 does not withdraw from painful stimuli, although most reflexes still function. Levels 3 and 4 are characterized by the absence of reflexes at level 4, respiratory action is depressed and the cardiovascular system fails. Among the many toxicants that cause coma are narcotic analgesics, alcohols, organophosphates, carbamates, lead, hydrocarbons, hydrogen sulfide, benzodiazepines, tricyclic antidepressants, isoniazid, phenothiazines, and opiates. 

The acute toxicity of methanethiol is similar to that of hydrogen sulfide. Inhalation of this gas can cause narcosis, headache, nausea, pulmonary irritation, and convulsions in humans. Other symptoms noted are acute hemolytic anemia, methemoglobinemia, and cyanosis. In humans, several hours exposure to about 5 ppm concentration of this gas can cause headache and nausea. Exposure to high concentrations can result in respiratory paralysis and death. The 2-hour... 

A. The mechanism of azide toxicity is unclear. Like cyanide and hydrogen sulfide, azide inhibits iron-containing respiratory enzymes such as cytochrome oxidase, resulting In cellular asphyxiation. Azide is also a potent, direct-acting vasodilator. 

II. Toxic dose. The characteristic rotten egg odor of hydrogen sulfide is detectable at concentrations as low as 0.025 ppm. The recommended workplace limit (ACGIH TLV-TWA) is 10 ppm (14 mg/m ) as an 8-hour time-weighted average, with a short-term exposure limit (STEL) of 15 ppm (21 mg/m ). The Federal OSHA permissible exposure limit (PEL) is 20 ppm as a 15-minute ceiling during an 8-hour workday. Marked respiratory tract irritation occurs with levels of 50-100 ppm. Olfactory nerve paralysis occurs with levels of 100-150 ppm. The level considered immediately dangerous to life or health (IDLH) is 100 ppm. Pulmonary edema occurs at levels of 300-500 ppm. Levels of 600-800 ppm are rapidly fatal. 

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