Pyridine (CAS #110-86-1) is a colorless liquid with an unpleasant smell which can be made
from crude coal tar or from other chemicals. It can also be formed from the breakdown of
many natural materials in the environment. It is used as a solvent in paint and rubber
preparation and in research laboratories for functions such as extracting plant hormones.
Approximately half the pyridine produced is used as an intermediate in making insecticides
and herbicides for agricultural applications.
Approximately 20% of pyridine produced goes into the production of piperidine, which is
commercially significant in the preparation of chemicals used in rubber vulcanization and
agriculture. It is also used directly in the denaturation of alcohol and to make many
different products such as medicines, vitamins, food flavorings, pesticides, paints, dyes,
rubber products, adhesives, and water proofing for fabrics.
Pyridine is flammable and volatile with steam; it mixes very easily with water and is
soluble in alcohol, ether, and benzene. When exposed to heat, flame, or oxidizers,
pyridine is a fire hazard. It is a severe explosion hazard in the form of vapor, when
exposed to flame or spark. When heated to decomposition, it emits highly toxic fumes of
cyanides; pyridine can react vigorously with oxidizing
materials. It is incompatible and reactive with strong oxidizers and strong acids, and
reacts violently with chlorosulfonic acid, maleic anhydride, oleum, perchromates,
B-propiolactone, formamide, chromium trioxide, and sulfuric acid. Liquid pyridine easily
evaporates into the air. If it is released to the air, it may take several months to years
until it breaks down into other compounds. Synonyms for pyridine are azabenzene and azine.
Chemical Name: Pyridine
Regulatory Name: Pyridine
DOT Label: Flammable Liquid
UN Number: 1282
Humans can be exposed to pyridine by inhaling it, absorbing it through the skin, ingesting
it, or making skin or eye contact with it. The most important health concern for humans
exposed to pyridine is damage to the liver. Other health concerns may be neurological
effects, renal effects, and irritation of the skin and eyes. Pyridine can cause central
nervous system depression, kidney and liver damage, and gastrointestinal upset. Exposure
can also cause headaches, nervousness, dizziness, insomnia, nausea, anorexia, frequent
urination, and dermatitis. Very few studies have been conducted to determine the other
possible effects of pyridine exposure on human health.
IDLH: 1000 ppm (NIOSH 1997)
TLV TWA: 5 ppm (ACGIH, 1999)
NIOSH REL: TWA 5 ppm (15 mg/m3)
OSHAPEL: TWA 5 ppm (15 mg/m3).
U.S. manufacturer of pyridine is Crowley Tar Products Company, Inc., Kent, OH.
Pyridine hydrochloride was produced in 1992 by R.S.A. Corporation, Ardsley, NY, and
Zeeland Chemical, Inc., Zeeland, MI. Refined pyridine, all other grades, was produced in
1992 by Reilly Industries, Inc., Indianapolis, IN. Production volumes are not available to
avoid disclosure of individual company operations, according to Synthetic Organic
Chemicals, United States Production and Sales, 1992, U.S. International Trade Commission.
Pyridine releases into the air are regulated by the Occupational Safety and Health
Administration (OSHA); The Food and Drug Administration (FDA) regulates pyridine as a food
additive, or synthetic flavoring substance component of polycarbonate, and as a resin, or
indirect food additive. EPA offices regulating pyridine are Emergency and Remedial
Response, Solid Waste, and Toxic Substances. Pyridine is regulated by the Resource
Conservation and Recovery Act, and the Comprehensive Environmental Response, Compensation
and Liability Act.
Under Section 313 of the Emergency Planning and Community Right to Know Act of 1986
releases of more than one pound of pyridine into the air, water, and land must be reported
annually and entered into the Toxic Release Inventory (TRI).
National Overview of 1998 Toxics Release Inventory
In 1998, 64 facilities released 681,047 pounds of pyridine. Of those releases, 70,902
pounds were air emissions; 1,056 pounds were surface water discharges; 593,204 pounds were
released by underground injection; none was released to land; and, 15,885 pounds were
transferred off-site for disposal. Total emissions for 1998 represented a decrease from
1997 emissions, which totaled 765,873 pounds; an iuncrease from 1996 emissions, which
totaled 521,666 pounds; an increase from 1995 emissions, which totaled 55,245 pounds; and
a decrease from 1988 (baseline) emissions, which totaled 787,556 pounds.
In 1998, 6,991,621 pounds of pyridine waste were managed; 616,015 pounds were recycled
on-site; none was recycled off-site; 1,759,911 pounds were used for energy recovery
on-site; 1,089,521 pounds were used for energy recovery off-site; 2,098,536 pounds were
treated on-site; 735,840 pounds were treated off-site; and 691,798 pounds were released
The 10 states in which the largest amounts of pyridine were released in 1998 were: Texas
(387,553 pounds); Ohio (170,942 pounds); Indiana (35,839 pounds); New York (28,037
pounds); Louisianna (21,241 pounds); Michigan (12,715 pounds); West Virginia (4,424
pounds); North Carolina (1,294 pounds); Tennessee (1,049 pounds); and Puerto Rico (500
The 10 facilities releasing the largest amounts of pyridine in 1997 were: Sterling
Chemicals Inc., Texas City, TX (251,296 pounds); Bp Chemicals Inc., Lima, OH (121,000
pounds); Merichem-Sasol Usa LLC, Houston, TX (75,520 pounds); BP Chemicals Inc., Port
Lavaca, TX (61,001 pounds); Pharmacia & Upjohn Co., Portage, MI (58,822 pounds); Cytec
Ind. Inc., Westwego, LA (30,000 pounds); Reilly Ind. Inc., Indianapolis, IN (29,300
pounds); Du Pont, Circleville, OH (20,962 pounds); Bethlehem Steel Corp., Burns Harbor, IN
(19,350 pounds); and Olin Chemicals & Chlor, Rochester, NY (13,400 pounds).
The NIOSH recommended exposure limits (RELs) are time-weighted average (TWA)
concentrations for up to a 10-hour workday during a 40-hour workweek. A short-term
exposure limit (STEL) is designated by "ST" preceding the value; unless noted otherwise,
the STEL is a 15-minute TWA exposure that should not be exceeded at any time during a
workday. A ceiling REL is designated by "C" preceding the value. Any substance that NIOSH
considers to be a potential occupational carcinogen is designated by the notation "Ca."
The OSHA permissible exposure limits (PEL) are found in Tables Z-1, Z-2, and Z-3 of the
OSHA General Industry Air Contaminants Standard (29 CFR 1910.1000). Unless noted
otherwise, PEL are TWA concentrations that must not be exceeded during any 8-hour
workshift of a 40-hour workweek. A STEL is designated by "ST" preceding the value and is
measured over a 15-minute period unless noted otherwise. OSHA ceiling concentrations
(designated by "C" preceding the value) must not be exceeded during any part of the
workday; if instantaneous monitoring is not feasible, the ceiling must be assessed as a
15-minute TWA exposure. In addition, there are a number of substances from Table Z-2
(e.g., beryllium, ethylene dibromide, etc.) that have PEL ceiling values that must not be
exceeded except for specified excursions. For example, a "5-minute maximum peak in any 2
hours" means that a 5-minute exposure above the ceiling value, but never above the maximum
peak, is allowed in any 2 hours during an 8-hour workday.
CDC National Institute for Occupational Safety & Health
Environmental Defense Scorecard: Chemical Profiles
Department of Health & Human Service National Toxicology Program
U.S. Environmental Protection Agency Acute Exposure Guideline Levels
National Institute of Environmental Health Sciences
TOXNET, National Library of Medicine
OSHA PEL Table Z-1
OSHA PEL Table Z-2
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