Hydrogen Sulfide (Essay Sample)

Hydrogen Sulfide
Physical Properties
Hydrogen sulfide is a colorless gas with a sweetish smell taste. It has a characteristic smell of rotten eggs and is heavier than air. It is a highly corrosive and toxic gas. It is highly flammable and can burn to produce poisonous sulfur dioxide gas. When inhaled, hydrogen sulfide inhibits the respiratory system (EPEA, 2003). The odor of hydrogen sulfide can be detected at low concentrations; which is the characteristic smell of rotten eggs. Hydrogen sulfide is produced naturally by some industrial processes and decaying matter (ATSDR, 2014). It is produced as a by-product of several industrial processes including mining, petroleum refinery, wood-pulp processing, tanning, rayon manufacturing, hot-asphalt paving and sugar-beet processing (ATSDR, 2014). It is released from sewage sludge; sulfur hot springs, liquid manure and natural gas (ATSDR, 2014). Exposure to high concentrations of hydrogen sulfide may not provide any warning because they lead to instant unconsciousness and death.
Hydrogen sulfide has a molecular weight of 34.08lb/mol. It has a boiling point of -770F and a melting point of -1220F (EPA, 2003). It is slightly soluble in water at 0.4 percent and 680F. The gas highly flammable and explosive at concentrations of between 4% and 45% in the air. It produces sulfur dioxide when it burns (ATSDR, 2014). According to EPA (2013), hydrogen sulfide is soluble in some polar organic solvents such as sulfolane, glycols, and acetone among others. It is also soluble in gasoline, crude oil, glycerol, carbon disulfide and kerosene.
Common Uses OF Hydrogen Sulfide
Hydrogen sulfide is formed when sulfur compounds are being removed from petroleum products and converted to elemental sulfur or sulfuric acid (ATSDR, 2014). Elemental sulfur formed from hydrogen sulfide is used for manufacture of fertilizers while sulfuric acid is used for various industrial purposes (ATSDR, 2014). According to ATSDR (2014), hydrogen sulfide is used in manufacture of thiophenes and sodium sulfide. It is used in chemical industries to protect iron or carbon steel from corrosion when exposed to salts. The gas is also used in production of heavy water for use in nuclear reactions and as a disinfectant in agriculture.
Hydrogen Sulfide Exposure Routes
Occupational exposure to hydrogen sulfide takes place primarily because of the gas presence in natural gas, petroleum, sewer gas, soil and a by-product of chemical reactions (EPA, 2003). Hydrogen sulfide is absorbed into the body through the lungs because it is a gas and is easily inhaled. It is usually inhaled and rapidly absorbed by the lungs and respiratory pathways (EPA, 200). When exposed to hydrogen sulfide, the victim experiences the rotten egg odor at a concentration of 0.5ppm. EPA (2003) however warns that this odor is not a reliable indicator of the gas presence and cannot be used to give warning of hydrogen sulfide hazardous concentrations. Furthermore, exposure at high concentrations may not give the victim time to identify the characteristic smell of rotten eggs because the patient loses consciousness, collapses and stops breathing.
Agency for Toxic Substances and Disease Registration, ATSDR (2014) points out to the fact that children exposed to same concentrations of hydrogen sulfide as adults may suffer more adverse effects because their lungs have a larger surface area to body ratio than that of adults. This increases their exposure levels. Moreover, children are usually nearer to the ground than adults because of their height and are prone to higher concentrations of hydrogen sulfide because the gas is denser than air and is more concentrated nearer to ground surface (ATSDR, 2014). Children are at a higher risk of hydrogen sulfide than adults because of their relatively small diameter of respiratory system airways that makes them more vulnerable to corrosive agents than adults.
ATSDR (2014) urges that even at lower concentrations of hydrogen sulfide, prolonged exposure may cause burning eyes and painful dermatitis. Direct skin contact with liquid hydrogen sulfide gas results to frostbite (ATSDR, 2014). Hydrogen sulfide absorption through the skin is minimal and therefore the main exposure route is human respiratory system. Ingestion of the gas is not likely to occur because hydrogen is a gas at room temperature (ATSDR, 2014). The main route for human exposure to hydrogen sulfide is the human respiratory system as the individual inhales the gas when exposed to it.
Toxicokinetics of Hydrogen Sulfide
Hydrogen sulfide is metabolized through oxidation, reactions with metalloproteinase and methylation (EPA, 2003). According to EPA (2003), the main pathway for hydrogen sulfide is oxidation in the liver and methylation as a minor pathway. Sulfate is the main oxidation product of hydrogen sulfide oxidation. Thiosulfate is sometimes isolated from tissues exposed to hydrogen sulfide. Through oxidation pathway, 69 percent of hydrogen sulfide is ionized (EPA, 2003). Studies reveal that lungs are the main target organs for hydrogen sulfide exposure. According to EPA (2003), hydrogen sulfide gas is widely distributed in human organs of the people exposed to it. Postmortem results for people who have died as a result of exposure to hydrogen sulfide have shown high levels of gas concentration in the liver, blood, lungs, brain, heart, spleen, and kidneys (EPA, 2003). This means that despite getting into human body through respiratory system, it has the ability to spread to other organs of the body.
Hydrogen sulfide mode of action in neurotoxicity cases is by altering pulmonary surfactants. EPA (2003) highlights that high hydrogen sulfide concentrations cause paralysis of ventilator center. Exposure to hydrogen sulfide concentrations of 50ppm results to a decline in CytOx activity in lungs mitochondria. Given the fact that CytOx is a terminal step for aerobic oxidation metabolism, inhibition by hydrogen sulfide results to development of hypoxia because it stops tissue respiration (EPA, 2003). Based on EPA (2003) report, studies have revealed that overexposure to hydrogen sulfide can cause direct neurotoxicity and lead to respiratory distress as well as other secondary adverse effects such as ataxia, motor weaknesses, nausea, headache, chest pain, dyspnea, and pulmonary edema among others. Hydrogen sulfide is eliminated from the body of those exposed to it through urine.
Hydrogen Sulfide Exposure Limits
OSHA ceiling for hydrogen sulfide is 20ppm and the maximum peak is 50ppm for ten minutes (ATSDR, 2014). The OSHA maximum air concentration of hydrogen sulfide concentration for which people can be exposed to for not more than one hour without experiencing irreversible or death symptoms and effects are 30ppm (ATSDR, 2014). Concentrations exceeding 100ppm have immediate danger to the victim’s health.
Hydrogen sulfide causes different health effects to people exposed to it at varying levels of concentration. Data from the Occupational Safety and Health Administration (2014) reveals that people working in industries are prone to hydrogen sulfide exposure by breathing it. Effects of the gas depend on how much gas one is exposed to and for how long. Exposure to high concentrations of hydrogen sulfide may lead to death. According to Occupational Safety and Health Administration (2014), typical background concentrations of hydrogen sulfide are between 0.00011 and 0.00033ppm. Concentrations between 0.01 and 1.15ppm are noticeable through a smell of rotten eggs, which becomes offensive when it reaches 3-5ppm. Hydrogen sulfide concentration of more than 30ppm produces a sweet or sickeningly sweet odor.
At concentration of between 2ppm and 5ppm, the victim may suffer nausea, headache, tearing of the eyes, loss of sleep and bronchial constriction (OSHA, 2014). Concentrations of 20ppm lead to fatigue, headache, and loss of appetite, poor memory, irritability and dizziness. Exposure to hydrogen sulfide concentrations of between 50ppm and 100ppm causes slight conjunctivitis and irritation on digestive system after one hour period of exposure (OSHA, 2014). Continued exposure at this concentration upsets digestive system and leads to loss of appetite. Exposure to hydrogen sulfide concentrations of 100ppm causes coughing, loss of smell, irritation of the eyes, drowsiness, altered breathing, irritation on the throat, and death after 48 hours of exposure.
Exposure to hydrogen sulfide concentrations of between 100ppm and 150ppm leads to loss of smell and may result to paralysis. Exposure to concentrations between 200 and 300ppm leads to marked conjunctivitis, irritation on respiratory tract and pulmonary edema after a prolonged exposure (OSHA, 2014). Exposure limits of between 500ppm and 700ppm of hydrogen sulfide cause staggering and the individual collapses after five minutes of exposure (OSHA, 2014). Continued exposure up to thirty minutes of hydrogen sulfide at this concentration leads to damage of the eyes within thirty minutes and death within 30 to 50 minutes. Exposure to concentrations between 700 and 1000ppm leads to rapid unconsciousness and immediate collapse (OSHA, 2014). Breathing stops and the victim dies within minutes. Exposure to the gas at concentration of 1000ppm and 2000ppm leads to instant death (OSHA, 2014). Consequences of hydrogen sulfide exposure reveal the level of health effects associated with the gas.
Acute Effects of Hydrogen Sulfide and Target Organs
Acute effects of exposure to hydrogen sulfide start at concentration of above 100ppm. The gas causes coughing, irritation of the eyes, fatigue, and irritation of the respiratory tract, drowsiness, throat irritation, and conjunctivitis (OSHA, 2014). More acute effects occur at exposure of more than 500ppm. At this concentration, the victim starts staggering, his eyes are damaged, and the victim loses consciousness, collapses, stops breath...