H

Hexane

CASRN 110-54-3

Physical Properties

n-Hexane is a chemical made from crude oil. Pure n-hexane is a colorless liquid with a slightly disagreeable odor. It evaporates very easily into the air, and dissolves only slightly in water. n-Hexane is flammable and may be ignited by heat, sparks, and flames. n-Hexane can react vigorously with oxidizing materials such as liquid chlorine, concentrated oxygen, and sodium hypochlorite. n-Hexane will attack some forms of plastics, rubber, and coatings.

Uses

Most of the n-hexane used in industry is mixed with similar chemicals in products known as solvents. Common names for some of these solvents are “commercial hexane,” “mixed hexanes,” “petroleum ether,” and “petroleum naphtha.” Several hundred million pounds of n-hexane are produced in the United States each year in the form of these solvents. The major use for solvents containing n-hexane is to extract vegetable oils from crops such as soybeans. They are also used as cleaning agents in the printing, textile, furniture, and shoemaking industries. Certain kinds of glues used in the roofing, shoe and leather industries also contain n-hexane. Several consumer products contain n-hexane. For example, gasoline contains about 1-3% n-hexane. n-Hexane is also present in rubber cement.

Sources of Exposure in Iowa

Since gasoline contains n-hexane, almost everyone is exposed to small amounts of n-hexane in the air. The n-hexane in gasoline is released into the air at service stations and in automobile exhaust. People who work in industries that use n-hexane, such as extracting vegetable oils from soybeans and other crops, may be exposed to larger amounts. Work situations where n-hexane is used as a solvent or adhesive, and where ventilation is poor, may also increase exposure risk. Workers in tire-manufacturing facilities may have increased health risk, since rubber vulcanization can expose them to n-hexane.

Health Effects from Large Acute Exposures

Initial exposure to large amounts of n-hexane by inhalation causes numbness in the feet and hands. This can be followed by muscle weakness in the feet and lower legs. If exposure continues, the symptoms can grow worse; in some cases, paralysis of the arms and legs can develop. Nerve damage, called “peripheral neuropathy,” may result (peripheral means outside the brain and spinal cord; neuropathy means nerve damage). Fortunately, once the exposure source is removed, the nerves can recover within 6 months to a year, although some severely affected individuals may not fully recover for 1 or 2 years.

Health Effects from Smaller, Chronic Exposures

Long-term exposure to lower concentrations of n-hexane may have similar neurological effects to exposure to larger amounts over shorter periods of time. There is no evidence that exposure to n-hexane increases the risk of cancer in humans. No reliable information is available on whether n-hexane causes cancer in animals.

Protection from Exposure

A person who works in an industry that uses n-hexane should work in a well-ventilated area, or use respiratory protection when necessary. Good ventilation and proper respiratory protection is also recommended for individuals who use n-hexane or other solvents at home.

Hydrogen Chloride

CASRN 7782-50-5

Physical Properties

At room temperature, hydrogen chloride is a colorless to slightly yellow gas with a pungent odor. On exposure to air, the gas forms dense white vapors due to condensation with atmospheric moisture. Hydrogen chloride can exist as a gas or as a liquid when mixed with water (hydrochloric acid or muriatic acid). The odor threshold of hydrogen chloride is 0.77 parts per million (ppm) or 1.15 milligrams per cubic meter (mg/m3) in air. The taste threshold of hydrogen chloride (hydrochloric acid) is 5.8 ppm. Hydrogen chloride gas is heavier than air and can collect in low-lying areas.

Uses

Hydrogen chloride is available commercially as an anhydrous (without water) gas or as an aqueous (water) solution (hydrochloric acid). Hydrochloric acid (also known as muriatic acid) is a component of commercial chemicals used to clean and disinfect swimming pools. In addition to cleaning hydrogen chloride is used for pickling and electroplating metals; in refining mineral ores; in petroleum well extraction; in leather tanning; and in the refining of fats, soaps, and edible oils. It is also used in producing polymers and plastics, rubber, fertilizers, dyes, dyestuffs, and pigments.

Source of Exposure in Iowa

Exposure of the general population to hydrogen chloride is not expected except in the case of an accidental spill or an industrial mishap. Occupational exposure to low levels of hydrogen chloride gas may occur with individuals who work at facilities that use or produce hydrogen chloride. Exposure to hydrochloric acid can occur in the science laboratory and during cleaning at swimming pools and other facilities that use hydrochloric acid as a cleaning agent.

Health Effects from Acute or Large Exposures

Concentrated hydrogen chloride can be corrosive to the skin, eyes, nose, mucous membranes, and respiratory and gastrointestinal tracts. Inhalation of hydrogen chloride can lead to pulmonary edema (accumulation of fluid in the lungs). The greatest impact is on the upper respiratory tract where exposure to high concentrations can rapidly lead to swelling and spasm of the throat and suffocation. Ingestion of concentrated amounts of hydrochloric acid can cause severe injury to the mouth, throat, esophagus, and stomach. Other effects of exposure include shock, circulatory collapse, metabolic disturbance, and respiratory depression. Deep burns of the skin and mucous membranes are caused by contact with concentrated hydrochloric acid or hydrogen chloride gas; and disfiguring scars may result. Contact with less concentrated acid or with vapor or mist can cause redness of the skin and mild inflammation.

Health Effects from Smaller, Chronic Exposures

Chronic or prolonged exposure to hydrogen chloride gas or to mist has been associated with changes in pulmonary function, chronic inflammation of the bronchi, nasal ulceration, and symptoms resembling acute viral infection of the upper respiratory tract as well as inflammation of the skin, discoloration and erosion of dental enamel, and inflammation of the eye membrane. There is not enough information to classify chlorine as carcinogenic.

Protection from Exposure

Proper safety equipment should be used when handling hydrogen chloride. Rubber gloves, respirators, and chemical splash goggles should be worn. Only 50% of exposed persons can perceive hydrogen chloride's odor at levels of concern, so odor may not provide adequate warning in the workplace.

Hydrogen Sulfide

CASRN 7783-06-4

Physical Properties

Hydrogen sulfide (H2S) is a heavier-than-air, colorless gas at room temperature with a sweetish taste and characteristic odor of rotten eggs. The odor threshold for hydrogen sulfide can range from 0.01 and below to 0.3 ppm (parts per million). Exposure to high concentrations of hydrogen sulfide (150 ppm) can paralyze the olfactory nerve, and our sense of smell can become rapidly fatigued. Therefore odor may not be a reliable indicator of the presence of hydrogen sulfide. Hydrogen sulfide gas is generally not corrosive, but hydrogen sulfide dissolved in water can be corrosive.

Uses

Natural gas and gases associated with crude oil contain hydrogen sulfide. Hydrogen sulfide’s major use is in the production of elemental sulfur sulfuric acid. Hydrogen sulfide is used to prepare inorganic sulfides, such as sodium sulfide and sodium hydrosulfide, which are used in the manufacture of dyes, rubber chemicals, pesticides, polymers, plastic additives, leather, and pharmaceuticals. Hydrogen sulfide is also used in the manufacture of metal sulfides. Hydrogen sulfide is used in the purification of nickel and manganese, in catalyst activation and poisoning, and in the treatment of metallic surfaces. It is also used in metallurgy, in the production of heavy water for the nuclear industry, and as an analytical reagent. It is used as an additive in extreme pressure lubricants and cutting oils. Hydrogen sulfide is also used as an agricultural disinfectant.

Source of Exposure in Iowa

Hydrogen sulfide occurs both naturally and from man-made processes. It is in the gases from swamps, and stagnant bodies of water and natural gas. Hydrogen sulfide also is associated with municipal sewers and sewage treatment plants, swine containment and manure-handling operations, and pulp and paper operations. Industrial sources of hydrogen sulfide include natural gas plants, food processing plants, and tanneries. Bacteria found in your mouth and gastrointestinal tract produce hydrogen sulfide during the digestion of food containing vegetable or animal proteins. Household exposures to hydrogen sulfide can occur through misuse of drain cleaning materials. Hydrogen sulfide can also be found in well water and formed in hot water heaters, giving tap water a rotten egg odor.

Health Effects from Acute or Large Exposures

Brief exposures to high concentrations of hydrogen sulfide gas (greater than 500 ppm) can cause a loss of consciousness. In most cases, the person who becomes exposed appears to regain consciousness without any other effects. However, in some individuals, there may be permanent or long-term effects such as headaches, poor attention span, poor memory, and poor motor function. Deaths due to breathing large amounts of hydrogen sulfide have been reported in a variety of different work settings, including sewers, animal confinement facilities, animal processing plants, waste dumps, sludge plants, and tanks and cesspools. Most of the fatal cases from exposure to hydrogen sulfide have occurred from exposure in relatively confined spaces. Very little information is available about health problems that could occur from drinking or eating something with hydrogen sulfide in it. Scientists have no reports of people poisoned by such exposures.

Health Effects from Smaller, Chronic Exposures

Exposure to low concentrations of hydrogen sulfide gas (above 2 ppm) may cause irritation to the eyes, nose, or throat. It may also cause difficulty in breathing for some asthmatics. There is not enough information to classify hydrogen sulfide as carcinogenic.

Protection from Exposure

Proper safety equipment should be used when there is a potential to be exposed to larger concentrations of hydrogen sulfide gas. Supplied-air respirators must be worn by individuals that need to work in an environment of high levels of hydrogen sulfide. Monitoring of levels of hydrogen sulfide in the air within confined spaces, such as sewers, are needed to assure that levels are safe for people to work.