Hexane: Necessary or Hazardous?
N-hexane is now being formulated into some brands of dry wash/cleaning solvents that are available to the embalming industry. This is a very poor choice of a solvent-type chemical for embalming usage. I fail to understand the logic of introducing another hazardous ingredient into the chemical mix of embalming, unless absolutely necessary and indispensable.
Such is not the case with n-hexane. Hexane and other hydrocarbon-style solvents are not far superior or exceptional in their solvent abilities compared to the acetone/alcohol solvent mixtures that are now being used as alternatives to the TCE/PERC (trichloroethylene/perchloroethylene) solvents that have massive exposure and disposal problems. The focus for modern embalming chemical formulation should be on the elimination of hazardous ingredients, if possible, and the reduction of overall total chemical exposure for the embalmer. There are already enough chemical exposures for embalmers; they do not need any additional exposures or other problems associated with new hazards.
Properties and Use
Hexane is a clear, slightly oil liquid with a disagreeable pungent gasoline-like odor. It is derived from crude oil/petroleum as an extract of a gasoline derivative components mix. It is insoluble in water and lighter in weight; therefore it floats on top of water if spilled. Hexane is also highly flammable and highly volatile, forming an explosive mixture if dispersed into air. The odor threshold is at least 65 ppm or much higher, which is problematic for sensory detection before overexposure.
The chemical is generally referred to as n-hexane, the straight chain isomer of hexane. You will also find “commercial hexane” or “petroleum naphtha or ether” and these refer to a complex mix of isomeric hexanes, heptanes, cyclohexane, methylcyclopentane, some smaller gasoline isomers and ketones. N-hexane usually accounts for 20-80 percent of these mixes. Gasoline itself contains typically 2-5 percent n-hexane. Hexane reacts vigorously with oxidizers and strong bleaching agents such as sodium and calcium hypochlorite. It attacks and softens rubber, latex, plastics and coatings. The vapors are much heavier than air and sink rapidly (vapor density equals 2.97 relative to air) and the vapor pressure is quite high at 150 mmHg, which results in a flammability problem. Several hundred million pounds of Hexane are used every year in the Untied States. It is predominantly used as a cost-effective extraction solvent for vegetable oils from various soybeans, cottonseeds, flax, corn and peanuts. It is also found in large quantities as a solvent and component of special glues for the shoe industry, roofing materials and leather joining uses. In addition, n-hexane is a cleaner/degreaser solvent in the printing industry, furniture finishing and shoemaking. It is also popular as a specialty solvent for automotive repair, involving brake shoes and brake pads cleaning and degreasing. It is used as the liquid in low-temperature thermometers and is present as the solvent in hobby and rubber cements. It has been used in book binding operations and in glue used to manufacture baseballs but not with cremation services/cremation costs.
Health Effects
In the atmosphere, n-hexane will break down by mostly hydroxyl radical oxidation in a matter of a few days. Consequently, half-lives in the environment are thankfully short. Hexane floats on top of water and usually evaporates without any serious pollution problems in surface water. Such is not the case in underground waters, such as wells and aquifers, where hexane accumulates and lingers. There is no essential soil action, accumulation or bioaccumulation in animals; therefore, the only serious problem is underground water supplies. The EPA has standardized a HA (Health Advisory Limit) of 4 ppm for water systems. Any water sources found above this level are advised to be remediated before human use. The major sources of pollution are leaking underground storage gasoline tanks, industrial spills and excessive releases by users.
The main sources of exposure for individuals are during use (from inhalation), splashing (skin contact) and spills (high level exposures). Everyone is exposed to some hexane in the air from diverse sources such as automobile exhaust in large cities, industrial emissions and filling up your gas tank on your car. Typically, in a large metropolitan city, the ambient hexane is present at two ppb (two parts per billion). Hexane is on four Federal Regulatory Lists and the TRI (Toxic Release Inventory). The main exposure problem areas for individual human exposures to hexane are refineries, shoe and leather factories, petrochemical lab technicians, typesetters and printers, tire and rubber workers and auto mechanics. After inhalation, hexane appears rapidly in the blood stream and is broken down and eliminated in a few days. Hexane is excreted in urine, along with its metabolites, and also exhaled back out of the lungs. Hexane does not bioaccumulate in the body. One of the metabolites of hexane, 2, 5-hexanedione, is more dangerous than hexane itself and is tracked in human urine as a bio-indicator of hexane exposure. 2, 5-hexanedione is the probable cause of the serious nerve damage and paralysis that can occur with high exposures to hexane. 2, 5-hexanedione will appear at four to five mg/L in urine of workers who have been exposed to 50 ppm hexane, which is over five times the amount found in the general population. Early symptoms and effects of hexane inhalation or exposure include vertigo, giddiness, headache and sensory impairment. Long term or high does exposures manifest several serious health effects that encompass paralysis, numbness of the feet, hands, and lower legs and various paresthesias. The medical diagnosis for this syndrome of symptom manifestation is generalized peripheral neuropathy, wherein definite nerve damage has occurred and paralysis is the result, if not corrected. Fortunately, in exposed workers the numbness and paralysis is usually recoverable and reversible within six months to one year after elimination of exposures. The cases of serious hexane exposures have drastically declined over the years due to elimination of hexane in many industries, reduced use and improved worker protection. Shoe workers were the most affected in the past, with very high numbers of overexposures reported. Serious overexposures reports are thankfully now rare, even in this high-use industry. Cancer has never been found to manifest in animal or human studies and most agencies do not consider it classifiable as a carcinogen. Testicular damage has been noted in high-exposure to rats and lung lesions in rabbits and mice. N-hexane is currently under review by the EPA for carcinogenic potential. Teratogenic (birth-defect causing) effects have not been consistently found and n-hexane is not classed as a teratogen, but as a chemical of interest in causation. A prenatal solvent exposure study found a correlation between n-hexane and other organic solvents to color vision defects in newborns of mothers that were exposed.