Chemical Data Notebook Series #19: Phenol
features
HAZARDOUS MATERIALS
Phenol, or carbolic acid, was used by early doctors as a cleansing agent before and after examination and surgery. They had just learned that bacteria are a cause of disease, and they realized that phenol is an excellent disinfectant.
What they didn’t realize was how potent it can be; many of those doctors suffered severe burns and systemic poisoning until they recognized that phenol is too toxic for constant use.
Today, phenol is still used as a commercial disinfectant, as well as in plastics, pharmaceuticals, adhesives, coatings, and agricultural and other chemicals. It’s also still very dangerous. Its toxic hazard is so great that many times the other hazards—phenol’s corrosive and combustible nature—may be forgotten.
Phenol may exist as a clear solid or a reddish liquid, with a familiar medicinal or disinfectant odor. That odor may not last long for someone exposed to the material, because the vapors may attack the olfactory nerve first and deaden the sense of smell.
At normal temperatures, phenol is corrosive to lead, aluminum, aluminum alloys, and plastics. When hot, it’s also corrosive to magnesium and zinc. The chemical is fairly stable, but it will react with strong oxidizers, alkaline materials, butadiene, and nitrobenzene.
The material’s flash point is 175° F, its ignition temperature is 1,319° F, and it has a flammable range of 1.5% to 8.6%. It has a specific gravity of 1.07, a molecular weight of 94, and a vapor density of 3.25. It boils at 359.2° F, freezes at 105.6° F, and is soluble in water.
Phenol’s molecular formula is C6H5OH. The large hexagonal portion of the chemical’s molecular structure is the benzene ring with the hydroxyl (-OH) radical attached. When this radical appears attached to a straightor branchedchain reaction, the resulting hydrocarbon derivative is an alcohol. Phenol picked up its common name of carbolic acid because of its corrosiveness; chemically, it’s not classified as an organic acid.
Although phenol is corrosive and combustible, by far the major hazard is its toxicity, which is effective through all routes of exposure to the body.
Phenol can be detected by smell in concentrations as low as 0.05 parts per million. Its short-term exposure limit (STEL) is 10 ppm for 15 minutes, and its threshold-limit value/time-weighted average (TLV/TWA) is 5 ppm for each 8 hours of a 40-hour work week. The level at which it’s immediately dangerous to life and health (IDLH) is 100 ppm.
Contact with the skin can be misleading, since no pain will be felt initially, nor will the skin redden immediately. Evidence of phenol’s corrosiveness will be felt, quite severely, sometime later. If the liquid contact isn’t terminated immediately, systemic poisoning symptoms will appear in addition to the pain caused by the burn. Death can result from absorption through the skin, with one reference claiming that contact on 64 square inches of human skin will be fatal in any time between 30 minutes and several hours.
Contact of the liquid with the eyes will cause severe damage and ultimately lead to blindness.
Contact with the vapors is just as bad. Skin exposure to the vapors can cause systemic or chronic poisoning just as rapidly as inhalation of the vapors, because phenol vapors are absorbed through the skin quite rapidly. The vapors also irritate the eyes, nose, and throat. Symptoms of systemic poisoning include coughing, difficulty in breathing, lung damage, twitching and convulsions, sudden collapse, and coma; eventually it can cause death. Chronic poisoning may produce symptoms that include difficulty in swallowing, vomiting, diarrhea, headaches, dizziness, and mental problems.
Syrtonyms
Baker’s P and S Liquid and Ointment
Benzenol
Benzophenyl
Carbolic acid
Carbolic oil
Hydroxybenzene
Middle oil
Monohydroxybenzene
NCI-C50124
Oxybenzene
Phenic acid
Phenyl alcohol
Phenyl hydrate
Phenyl hydroxide
Phenylic acid
Phenylic alcohol
Resource Conservation and Recovery Act Waste Number U188
Identification Numbers and Ratings
UN/NA
(United Nations/North America)
UN/NA 2821 for the liquid or solution
UN/NA 1671 for the solid
UN/NA 2312 for the molten material
National Fire Protection Association 704 rating
3-2-0
CAS
(Chemical Abstract Service)
108-95-2
RTECS
(Registry of Toxic Effects of Chemical Substances)
National Institute of Occupational Safety and Health
SJ3325000
STCC
(Standard Transportation Commodity Code)
Association of American Railroads, Bureau of Explosives
4921210 for the liquid
4921220 for the solid
CHRIS
(Chemical Hazard Response Information System)
U.S. Coast Guard
CBO
U.S. Department of Transportation
Poison B
IMO
(International Maritime Organization)
6.1, poisonous substance
Lethal amounts of phenol by ingestion may be as little as 1 gram (0.03 ounce). Ingestion of lessthan-lethal amounts will produce nausea and jaundice.
Phenol’s corrosive nature is usually discussed in terms of other materials, since contact with humans in sufficient purity and quantity will cause death. However, solutions of phenol and water are often used for industrial purposes. And these solutions, although they may not prove fatal, can cause corrosive burns to human skin.
With a flash point of 175° F, phenol is combustible, a hazard often overshadowed by toxicity. The chemical’s ignition temperature is fairly high and its volatility is fairly low. However, with the generation of vapors, the relatively high vapor density means those vapors will hang together, seeking out low spots in the ground, and flowing along those low spots seeking an ignition source. Any release of the liquid will generate enough vapors to flow great distances and, upon ignition, will flash back to the original source.
Nonfire situations
If phenol has been released in quantity, such as in a spill or leak from a large container, all of its hazards must be considered. Since the toxicity is so high, release of the vapors and their travel toward populated areas must be avoided. If vapors can’t be controlled, evacuation downwind must be considered right away.
Approach to the spill must be from upwind, with all ignition sources eliminated. Care must be taken because, even when emergency personnel wear self-contained breathing apparatus, there’s no guarantee against systemic poisoning. SCBA can protect the lungs, but any exposed area of the body will provide an entry site for the vapors, as well as the liquid.
Since phenol’s volatility is low, large amounts of vapor may not be generated if the ambient temperature isn’t high. Released vapors can be swept from the air by an application of water spray or fog, which will dissolve them. The resuiting water must be collected and contained.
The spread of spilled phenol must be controlled immediately. Containment dikes may be constructed of soil, sand, clay, or other absorbent materials. A containment pit may be constructed, and trenches may be dug from the spill to the pit. But it’s extremely important to keep in mind that the phenol will contaminate any soil it contacts. The amount will increase with the size of the pond, pit, and trenches. Remember that all contaminated soil will have to be removed after the incident. A great deal of time and money will be saved by lining the containment pond, pit, and trenches with an impervious material to prevent percolation of the product into the soil.
If the containment pond is small enough, sheets of plastic or other resistant material may be used to cover the surface, which slows the generation of vapors. It may be preferable to dig a containment pit, since such pits usually have smaller surface areas than containment ponds, and these can be covered easily.
Glossary
Alkaline—Any substance that’s basic (rather than acidic) in water solutions. Usually pertains to hydroxides.
Hydrocarbon derivative—A compound that began as a hydrocarbon and has had a radical substituted for a hydrogen atom.
Neutralization—The chemical reaction in which acids and bases react to form a salt and water.
Radical—An atom, or a group of atoms bound together chemically, that will impart a particular set of chemical properties to a compound. Also known as a free radical.
Volatility—The tendency of a liquid to pass into the vapor state at a given temperature.
The application of foam may also slow the generation of vapors from the spilled liquid. Alcoholtype foams may work the best, but your foam supplier is the best adviser for this technique. As the foam breaks down, volume is added to the liquid, possibly increasing containment problems.
Phenol must be prevented from entering waterways. If it gets into them, all downstream users must be notified, particularly any who might draw drinking water from the stream or river. Industrial users also face a danger, since any water drawn into their operation will produce toxic and flammable vapors upon exposure to heat.
Any phenol accumulated at the site should be pumped into secure containers as soon as possible. Because of the product’s corrosiveness, equipment chosen to pump or otherwise handle phenol must be resistant to it. Operators of such equipment must be fully protected from any exposure to the product in liquid or vapor form.
If a tanker or tank car is leaking, a holding tank constructed of phenol-resistant material can be used to catch the leak and contain the material, allowing it to be pumped directly back into the leaking container until a secure container is obtained. This “semi-closed” system works only if the leaking product can be easily collected at the source of the leak.
Phenol may be absorbed by the same sort of materials used in the containment pit, or cement powder, fly ash, or peat moss. This depends, of course, on the amount of absorbent material available. The amount of liquid should be reduced as much as possible before any absorption is attempted. In any event, once the phenol is absorbed, the contaminated absorbent must be disposed of in a manner in accordance with federal, state, and local regulations. These clean-up and disposal procedures must always be handled by a professional, qualified salvage team, and not by emergency personnel.
In the case of water contaminated by phenol, activated charcoal may be used to adsorb the product. Adsorption is the adherence of one material to the surface of another, as opposed to absorption, in which one material actually penetrates the other. The adsorption procedure is more complicated and may require dredging the waterway after application of the activated carbon. Again, once the material is adsorbed, it must be properly disposed of. In both absorption and adsorption, the contaminated material has all the hazards of the original product.
Neutralizing the phenol is another possible strategy, but there are no published neutralization agents listed. Fire departments whose jurisdictions include companies that use phenol, and those that are sure large volumes of phenol move through their jurisdiction, may want to contact manufacturers of the product for their recommendations. As always, if a neutralization agent is to be used, it should first be tested on a small amount of the material to be neutralized. Often, the technique used and the strengths and hazards of the neutralizing agent make the difference between safe and tragic consequences.
Where the material is burning, precautions must be taken to prevent toxic combustion products— large amounts of carbon monoxide and small amounts of unburned phenol—from harming humans, and all exposures must be protected. Wherever containers of phenol are exposed to impinging flame or radiated heat, they must be kept as cool as possible. Although a BLEVE (boiling-liquid, expandingvapor explosion) technically doesn’t occur with containers of liquid, it’s possible for an overheated container to fail catastrophically and release burning phenol in a pressure-relief explosion.
Phenol burns hot and dirty, generating a lot of heat and smoke. Any metal exposed to the fire will be heated to temperatures far above phenol’s ignition. So after the fire is extinguished, there’s a possibility of reignition because of the hot metal. Extinguishing agents include carbon dioxide, dry chemical foam, and water. If the fire is in the containment pond or pit, and that pond or pit is large enough, dilution can be used in addition to water spray and fog. Since phenol is soluble if enough water is added, the phenol will dissolve to form a solution with a considerably higher flash point, and that solution will simply quit producing enough vapors to form an ignitable mixture near the surface of the liquid. This technique will work only if there’s enough room in the pit or pond (or container, for that matter) to hold all the additional water needed.
If burning liquid reaches a waterway, the fire will be put out in the same manner as the pit or pond dilution. However, in both cases, there’s the problem of the remaining toxic material. And in the case of the waterway, the stillpresent toxic material is moving downstream. Recovery by adsorption through activated charcoal is called for.
In responding to an incident involving phenol, all emergency personnel must be totally protected from exposure to the vapors. Any equipment and clothing worn must prevent the possibility of skin or eye contact with liquid phenol, and skin, eye, or lung contact with the vapors. If personnel must work in or very near the liquid where any chance of contact exists, fully encapsulating suits of impervious material must be worn.
Manufacturers of such suits say that impervious material includes Butyl rubber, chlorinated polyethylene, natural rubber, neoprene, and polyethylene. Phenol is such a common material that protection against it as well as other common hazardous materials should be a prerequisite of the suit’s purchase.
The suits should be worn with positive-pressure SCBA. Some references suggest canister masks for low concentrations. But since phenol is so toxic, unnecessary risks shouldn’t be taken.
Many firefighters don’t wear SCBA when fighting outdoor fires, but even if they did in this case, it wouldn’t be enough protection. A total encapsulating suit may not be necessary to protect against vapors alone, but all exposed skin must be covered. All sleeves and pant legs should be taped down to prevent vapors from entering.
A victim of phenol inhalation must be moved to fresh air immediately, and artificial respiration must be administered if breathing becomes difficult. The rescuer should be careful: This process may expose the provider of first aid to toxic vapors from the victim’s lungs.
For ingestion, if the victim is conscious, large quantities of water must be administered and vomiting induced. If the victim is unconscious, never introduce liquids; transport the person to competent medical assistance immediately.
For skin contact, wash contacted areas of the body with large amounts of soap and water. If contact involves the eyes, flush with clean water for at least 15 minutes, occasionally lifting the eyelids.
In each case, phenol’s extreme toxicity requires that the victim get immediate medical attention.
