IPCS INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
Health and Safety Guide No. 59
n-HEXANE
HEALTH AND SAFETY GUIDE
UNITED NATIONS ENVIRONMENT PROGRAMME
INTERNATIONAL LABOUR ORGANISATION
WORLD HEALTH ORGANIZATION
WORLD HEALTH ORGANIZATION, GENEVA 1991
This is a companion volume to Environmental Health Criteria 122:
n-Hexane
Published by the World Health Organization for the International
Programme on Chemical Safety (a collaborative programme of the United
Nations Environment Programme, the International Labour Organisation,
and the World Health Organization)
This report contains the collective views of an international group of
experts and does not necessarily represent the decisions or the stated
policy of the United Nations Environment Programme, the International
Labour Organisation, or the World Health Organization
WHO Library Cataloguing in Publication Data
Health and safety guide for n-Hexane
(Health and safety guide ; no. 59
1.Hexanes - standards I.Series
ISBN 92 4 151059 5 (NLM Classification: QV 633)
ISSN 0259-7268
The World Health Organization welcomes requests for permission to
reproduce or translate its publications, in part or in full.
Applications and enquiries should be addressed to the Office of
Publications, World Health Organization, Geneva, Switzerland, which
will be glad to provide the latest information on any changes made to
the text, plans for new editions, and reprints and translations
already available.
(c) World Health Organization 1991
Publications of the World Health Organization enjoy copyright
protection in accordance with the provisions of Protocol 2 of the
Universal Copyright Convention. All rights reserved.
The designations employed and the presentation of the material in this
publication do not imply the expression of any opinion whatsoever on
the part of the Secretariat of the World Health Organization
concerning the legal status of any country, territory, city or area or
of its authorities, or concerning the delimitation of its frontiers or
boundaries.
The mention of specific companies or of certain manufacturers'
products does not imply that they are endorsed or recommended by the
World Health Organization in preference to others of a similar nature
that are not mentioned. Errors and omissions excepted, the names of
proprietary products are distinguished by initial capital letters.
CONTENTS
INTRODUCTION
1. PRODUCT IDENTITY AND USES
1.1. Identity
1.2. Physical and chemical properties
1.3. Analytical methods
1.4. Uses
2. SUMMARY AND EVALUATION
2.1. Human exposure to n-hexane
2.2. Uptake, metabolism, and excretion
2.3. Effects on animals
2.4. Effects on human beings
3. CONCLUSIONS AND RECOMMENDATIONS
4. HUMAN HEALTH HAZARDS, PREVENTION AND PROTECTION, EMERGENCY
ACTION
4.1. Main human health hazards, prevention and protection,
first aid
4.1.1. Advice to physicians
4.1.1.1 Symptoms of poisoning
4.1.1.2 Medical advice
4.1.2. Health surveillance advice
4.2. Safety in use
4.3. Explosion and fire hazards
4.3.1. Flammability and explosion
4.3.2. Fire
4.4. Storage
4.5. Transport
4.6. Spillage and disposal
4.6.1. Spillage
4.6.2. Disposal
5. HAZARDS FOR THE ENVIRONMENT AND THEIR PREVENTION
6. SUMMARY OF CHEMICAL SAFETY INFORMATION
7. CURRENT REGULATIONS, GUIDELINES, AND STANDARDS
7.1. Regulation of emissions
7.2. Regulation of food
7.3. Exposure limit values
7.4. Labelling and packaging
BIBLIOGRAPHY
INTRODUCTION
The Environmental Health Criteria (EHC) documents produced by the
International Programme on Chemical Safety include an assessment of
the effects on the environment and on human health of exposure to a
chemical or combination of chemicals, or physical or biological
agents. They also provide guidelines for setting exposure limits.
The purpose of a Health and Safety Guide is to facilitate the
application of these guidelines in national chemical safety
programmes. The first three sections of a Health and Safety Guide
highlight the relevant technical information in the corresponding EHC.
Section 4 includes advice on preventive and protective measures and
emergency action; health workers should be thoroughly familiar with
the medical information to ensure that they can act efficiently in an
emergency. Within the Guide is a Summary of Chemical Safety
Information which should be readily available, and should be clearly
explained, to all who could come into contact with the chemical. The
section on regulatory information has been extracted from the legal
file of the International Register of Potentially Toxic Chemicals
(IRPTC) and from other United Nations sources.
The target readership includes occupational health services, those in
ministries, governmental agencies, industry, and trade unions who are
involved in the safe use of chemicals and the avoidance of
environmental health hazards, and those wanting more information on
this topic. An attempt has been made to use only terms that will be
familiar to the intended user. However, sections 1 and 2 inevitably
contain some technical terms. A bibliography has been included for
readers who require further background information.
Revision of the information in this Guide will take place in due
course, and the eventual aim is to use standardized terminology.
Comments on any difficulties encountered in using the Guide would be
very helpful and should be addressed to:
The Manager
International Programme on Chemical Safety
Division of Environmental Health
World Health Organization
1211 Geneva 27
Switzerland
THE INFORMATION IN THIS GUIDE SHOULD BE CONSIDERED AS A STARTING POINT
TO A COMPREHENSIVE HEALTH AND SALTY PROGRAMME
1. PRODUCT IDENTITY AND USES
1.1 Identity
Common name: n-hexane (normal hexane)
Chemical structure: H H H H H H
' ' ' ' ' '
H - C - C - C - C - C - C - H
' ' ' ' ' '
H H H H H H
Chemical formula: C6H14
Relative molecular
mass: 86.18
CAS registry
number: 110-54-3
RTECS registry
number: MN9275000
Purity: Purified material contains 95-99.5% n-hexane
with small amounts of other hexane isomers as
impurities. Commercial hexane contains a
mixture of hexane isomers ( n-hexane, 2-methyl
pentane, 3-methyl pentane, 2,3-dimethyl
butane), cyclohexane, methyl cyclopentane,
pentane and heptane isomers, acetone, methyl
ethyl ketone, dichloromethane, and
trichloroethylene. Phthalate esters, adipate
esters, and organophosphorous compounds have
been identified as minor components. The
n-hexane content of commercial hexane varies
from 20 to 80%.
1.2 Physical and Chemical Properties
n-Hexane is a colourless, highly volatile liquid that is poorly
soluble in water and is miscible with most organic solvents.
Commercial hexane has been reported as having a slightly disagreeable
odour; the odour threshold is approximately 210 mg/m3 (60 ppm).
Some physical and chemical properties of n-hexane are given in the
Summary of Chemical Safety Information (section 6).
n-Hexane is dangerous when exposed to heat, flame, or oxidizing
materials.
1.3 Analytical Methods
Gas chromatography combined with flame ionization or mass spectroscopy
is a suitable technique for the determination of n-hexane in air,
liquids, or biological samples. Metabolites of n-hexane can be
determined using high performance liquid chromatography.
1.4 Uses
n-Hexane is most often used commercially in the form of a mixture
with other hexane isomers and other solvents. Hexanes are mainly used:
for the extraction of vegetable oil from soybeans, flaxseed, peanuts,
safflower, corn germ, and cottonseed; as solvents in various products,
including the polyolefins; and as solvents in industrial processes,
such as rubber polymerization. n-Hexane is also used: as a
cleaning agent; as a laboratory chemical; in food processing; in
low-temperature thermometers; and in other products (e.g., adhesives
and lacquers).
2. SUMMARY AND EVALUATION
2.1 Human Exposure to n-Hexane
n-Hexane can be isolated from natural gas and crude oil. It is used
in food processing, including the extraction of vegetable oils, and as
a solvent in various products and processes. In the atmosphere, the
half-life of n-hexane is estimated to be less than 2 days.
Occupational exposure to n-hexane is mainly via inhalation, though
skin and eye contamination may also occur.
2.2 Uptake, Metabolism, and Excretion
In mammals, n-hexane is absorbed rapidly through the lungs and is
distributed widely in the adult body, as well as to fetal tissues.
Dermal absorption is limited. n-Hexane undergoes oxidative
metabolism to form a number of metabolites, including 2,5-hexanedione,
which is thought to be the neurotoxic agent. Particularly high levels
of n-hexane and 2,5-hexanedione can be found in the sciatic nerve of
exposed rats. Most n-hexane is excreted unchanged in exhaled air and
as metabolites in exhaled air and urine.
2.3 Effects on Animals
The acute toxicity of n-hexane is low, with reported LD50 values
in the range of 15-30 g/kg and an LC50 (1-h) of 271040 mg/m3.
Testicular toxicity and neurotoxicity, both peripheral and central,
appear to be the principal toxic effects of repeated n-hexane
exposure in rats. Irreversible testicular lesions were seen in rats
exposed to 17 600 mg/m3 (5000 ppm) for 16 h/day, 6 days/week, for 2
weeks. The metabolite 2,5-hexanedione also produced testicular
toxicity following oral exposure in rats.
The neurotoxic effect of n-hexane is characterized clinically by
hind limb weakness, which can progress to paralysis. Clinical signs
have been seen in rats after a 10-week exposure to 560 mg/m3
(3000 ppm) for 12 h/day and 7 days/week. Axonal swellings have been
observed in hind limb nerves, and in the brain and spinal cord, prior
to the appearance of hind limb weakness. A no-observed-effect level
(NOEL) was not established in continuous, 6-month, inhalation studies;
nerve lesions were seen at n-hexane levels of 1760 mg/m3 (500 ppm)
or more. n-Hexane-induced neurotoxicity can be enhanced by combined
exposure to methyl ethyl ketone, methyl isobutyl ketone, and lead
acetate. The lungs, kidneys, and liver have also been reported to be
affected by the inhalation of n-hexane at relatively high
concentrations.
Severe microscopic lesions were noted in the skin following the dermal
application of n-hexane, under occlusive dressings, for short
periods. Prolonged exposure to 10 560 mg n-hexane/m3 (3000 ppm)
caused conjunctival irritation in the eyes of rats and ocular
irritation in rabbits.
There is no evidence of embryotoxicity or teratogenicity in rats or
mice, but these aspects have not been studied adequately.
The carcinogenic potential of n-hexane has also not been studied
adequately. The results of assays for point mutations and for DNA
repair in bacterial and mammalian cells were negative, though there is
evidence for the production of chromosomal aberrations in vitro and
in vivo. The results were also negative in a limited study on skin
rumour formation in mice treated with n-hexane.
2.4 Effects on Human Beings
The available data suggest that the acute toxicity of n-hexane is
low. Single exposures to n-hexane can cause vertigo, giddiness, and
drowsiness. n-Hexane is a mild skin irritant that causes transient
erythema when in short-term contact with skin; it can also irritate
the eyes. There are no reports of skin sensitization.
A number of studies have linked occupational exposure to n-hexane
with the incidence of peripheral neuropathy, though adequate exposure
data have usually been lacking. Exposure to air concentrations of
n-hexane reported to have varied from 106 mg/m (30 ppm) to 8800 mg/m3
(2500 ppm), has been associated with neuropathy, but the previous
exposures of these cases may have been higher. Mild subclinical
neurological effects have been reported from cross-sectional studies
on workers exposed to 70-352 mg n-hexane/m (20-100 ppm), but no
cases of clinically overt peripheral neuropathy were identified at
these concentrations.
Thus, while there is evidence for an effect of n-hexane on the
central nervous system, it is not possible to relate this to defined
exposure levels, on the basis of the available information.
3. CONCLUSIONS AND RECOMMENDATIONS
n-Hexane is unlikely to present hazards for the environment, except
in the case of major spills or discharges, where there could be
transient local effects.
On the information available, it is concluded that workers who come
into contact with n-hexane will not be at risk, providing exposure
levels in the workplace are kept within the prescribed control limits.
Because of the mild irritant effects of n-hexane and the possibility
of skin absorption, contact with the skin and eyes should be avoided.
4. HUMAN HEALTH HAZARDS, PREVENTION AND PROTECTION, EMERGENCY ACTION
4.1 Main Human Health Hazards, Prevention and Protection, First Aid
The principal adverse effect of exposure to n-hexane is
neurotoxicity. It is therefore essential that appropriate precautions
should be taken during handling and use.
4.1.1 Advice to physicians
4.1.1.1 Symptoms of poisoning
A single exposure to n-hexane can produce vertigo, giddiness, and
drowsiness. Longer-term exposures can lead to peripheral neuropathy,
the first signs of which are symmetrical paraesthesia and weakness,
particularly in the lower extremities. Headache, anorexia, dizziness,
and sensory impairment may precede, or accompany, the neuropathy. Most
patients show diminished reflexes; there may be loss of body weight.
4.1.1.2 Medical advice
In case of poisoning by n-hexane, the nearest Poisons Information
Centre should be contacted for detailed advice on treatment.
Information on first aid is provided in the Summary of Chemical Safety
Information (section 6). If breathing has stopped, artificial
respiration and oxygen should be applied. Following ingestion,
vomiting should not be induced, because of the danger of aspiration
into the lungs. Gastric lavage should only be given where aspiration
into the lungs can be avoided by the use of a cuffed endotracheal
tube.
4.1.2 Health surveillance advice
A pre-employment medical examination is advisable for workers who will
be regularly exposed to n-hexane. In routine medical checks,
emphasis should be placed on examination of the central and peripheral
nervous system and male reproductive function.
4.2 Safety In Use
Atmospheric levels should be kept as low as practicable, and certainly
below the recommended occupational exposure limits, by suitably
designed work processes and by engineering controls, such as local
exhaust ventilation. Protective clothing, resistant to permeation by
n-hexane, and approved, effective, respiratory protection should be
readily available for use in enclosed spaces, in case of emergencies,
and for certain maintenance operations.
4.3 Explosion and Fire Hazards
4.3.1 Flammability and explosion
n-Hexane is highly flammable. Adequate ventilation should be
provided and smoking prohibited. There should be no sources of sparks
or heat, and electrical equipment should be designed according to a
recognized explosion-proof standard.
4.3.2 Fire
Flashback along a vapour trail may occur, since the vapour is heavier
than air. Fire extinguishers containing carbon dioxide, dry chemical,
or foam are recommended. Water sprays should not be used, since these
may cause the fire to spread, though a water spray can be used to cool
containers.
4.4 Storage
Drums should be stored in a well-ventilated area in fire-resistant
containers. Metal containers should be electrically-grounded, when
liquid is being transferred.
4.5 Transport
Comply with legal and other requirements regarding the transport of
hazardous material. Containers should be in good condition and
properly labelled, and should be kept in a well-ventilated place, away
from sources of ignition.
4.6 Spillage and Disposal
4.6.1 Spillage
In the event of spillage, naked flames, sparks, and heat should be
avoided; approved, efficient, protective clothing and respirators
should be provided. Small-scale spillage should be absorbed on paper
towels or sawdust; sand or earth can be used for larger spills.
Fire-fighting foam can be used in large spillages to reduce
evaporation. If possible, liquid spills should be recovered for
recycling.
4.6.2 Disposal
The International Register of Potentially Toxic Chemicals recommends:
"Incineration, open burning, use as a boiler fuel, evaporation. Spray
into the furnace. Incineration will become easier by mixing with a
more flammable solvent. Care, highly inflammable, evaporate only small
amounts. Landfill is not recommended".
5. HAZARDS FOR THE ENVIRONMENT AND THEIR PREVENTION
Industrial discharges from the manufacture, formulation, or technical
applications of n-hexane should be minimized and may be regulated
(section 7). With adequate controls, n-hexane in the environment is
not likely to produce toxic effects on aquatic organisms, since the
LC50 is reported to be greater than 1000 mg/litre (1000 ppm).
It is not expected to have any marked effect on the physical
properties of the atmosphere and its half-life in the atmosphere is
estimated to be less than 2 days.
6. SUMMARY OF CHEMICAL SAFETY INFORMATION
This summary should be easily available to all health workers
concerned with, and users of, n-hexane. It should be displayed at, or
treat, entrances to areas where there is potential exposure to
n-hexane, and on processing equipment and containers. The summary
should be translated into the appropriate language(s). All persons
potentially exposed to the chemical should also have the instructions
in the summary clearly explained.
Space is available for insertion of the National Occupational
Exposure Limit, the address and telephone number of the National
Poison Control Centre, and local trade names.
n-HEXANE
Chemical formula: C6H14
CAS registry number: 110-54-3: RTECS registry number: MN9275000
PHYSICAL PROPERTIES OTHER CHARACTERISTICS
Boiling point (°C) 69 Colourless, volatile liquid; commercial
Melting point (°C) -95 hexane has a slightly disagreeable odour with an
Relative density (D420) 0.6603 odour threshold of approximately 210 mg/m3 (60 ppm)
Vapour pressure (mmHg) (25°C) 150
Relative molecular mass 86.18
1-Octanol/water partition
coefficient (log Pow; 25°C) 3.6
Solubility in water (mg/litre) (25°C) 9.5
Solubility in solvents soluble in most solvents
including ethanol
Vapour density 2.97
Autoignition temperature (°C) 225
Explosive limits in air (% by volume) 1.1-7.5
Closed-cup flash point (°C) -21.7
HAZARDS/SYMPTOMS PREVENTION AND PROTECTION FIRST AID
Vapour/fumes
EYES: Irritation and lacrimation; Proper containment or efficient local Remove from exposure; irrigate eyes for at
discomfort, pain, red eyes, blurred exhaust ventilation, so that breathing least 15 minutes with a gentle flow of fresh
vision zone concentrations are below the potable water or sterile eye irrigation fluid;
occupational exposure limit; otherwise, send to a doctor
positive pressure demand, compressed
air, breathing apparatus or other
effective respiratory protection
with full facepiece should be worn,
so that complete protection of the
eyes and respiratory tract is assured
SKIN: n-Hexane can be Avoid skin contact, wear protective Remove contaminated clothing immediately;
absorbed through the skin; clothing resistant to permeation the skin should be thoroughly washed with
it may also cause dry skin or by n-hexane soap and plenty of water
inflammation
INHALATION: Affects the nervous Control levels in the work environment Remove patient to fresh air and keep warm;
system; vertigo, giddiness, drowsiness; to within recommended exposure limit; if breathing has stopped,. apply artificial
long-term exposures have produced otherwise provide respiratory respiration; obtain medical attention
peripheral neuropathy protection, such as a supplied-air
respirator or self-contained, breathing
apparatus
INGESTION: Abdominal pain; Do not eat, drink, or smoke during Vomiting should not be induced; keep
nausea and, if absorbed, symptoms work patient warm; obtain medical attention
of nervous system effects, similar to
those following inhalation; should
not occur with good work practices
HAZARDS/SYMPTOMS PREVENTION AND PROTECTION FIRST AID
ENVIRONMENT: Should not Industrial discharges should be
pose a risk, provided that there are minimized and may be regulated
adequate controls to minimize
emissions
SPILLAGE STORAGE FIRE AND EXPLOSION
Take appropriate personal Store drums in a well-ventilated Adequate ventilation should be provided
precautions; absorb spillage on area, in fire-resistant containers; and there should be no sources of sparks,
paper towels, sawdust, earth, or metal containers should be heat, or naked flames; flashback along a
sand, for subsequent incineration; electrically-grounded, when liquid vapour trail may occur; fire extinguishers
if possible, liquid spills should be is being transferred containing carbon dioxide, dry chemical,
recovered for recycling or foam are recommended; water sprays
should not be used, except to cool containers
WASTE DISPOSAL LABELLING
Waste material should be National Occupational Exposure United Nations
incinerated in an approved; Limit: Hazard Class 3.1 (flammable liquid)
manner; disposal should not be Packaging Class II (medium danger)
via landfill burial, or drains National Poison Control Centre:
Local trade names:
7. CURRENT REGULATIONS, GUIDELINES, AND STANDARDS
The information given in this section has been extracted from the
International Register of Potentially Toxic Chemicals (IRPTC) legal
file. A full reference to the original national document from which
the information was extracted can be obtained from IRPTC. When no
effective date appears in the IRPTC legal file, the year of the
reference from which the data are taken is indicated by (r).
The reader should be aware that regulatory decisions about chemicals,
taken in a certain country, can only be fully understood in the
framework of the legislation of that country The regulations and
guidelines of all countries are subject to change and should always be
verified with appropriate regulatory authorities before application
7.1 Regulation of Emissions
In the Federal Republic of Germany, n-hexane belongs to Class III
substances, the total emission of which (as a sum of all compounds in
this class) must not exceed 150 mg/m3, at a mass flow of 3 kg/h. In
the USER, the ambient air concentration of n-hexane must not exceed
300 mg/m3.
7.2 Regulation of Food
FAO/WHO have not allocated an acceptable daily intake for n-hexane,
but recommend that the solvent should be used only in accordance with
good manufacturing practice, to ensure minimal residues in food.
In the USA, cottonseed products and hop extract, modified for human
consumption, must contain not more than 60 mg n-hexane/kg and 25 mg
n-hexane/kg, respectively. The latter limit also applies to specified
food colouring agents containing n-hexane.
7.3 Exposure Limit Values
Some exposure limit values are given in the following table.
7.4 Labelling and Packaging
The United Nations places n-hexane in Hazard Class 3.1, flammable
liquid. For packaging, the United Nations places n-hexane in Group
II, substance presenting medium danger.
In the EEC, n-hexane is classified as a harmful substance (Class II/A)
and n-hexane and mixtures (if n-hexane is more than 5% of a
mixture) should be labelled as follows:
Highly flammable. Hazard by inhalation and in contact with skin.
Possible risks of irreversible effects. Keep container in a
well-ventilated place. Keep away from sources of ignition -
no smoking. Do not breathe gas/fumes/vapour/spray.
In the United Kingdom, road tankers transporting n-hexane must be
labelled "Flammable liquid".
OCCUPATIONAL AIR EXPOSURE LIMIT VALUES
Country Exposure limit descriptiona Value Effectiveb date
Australia Threshold limit value (TLV)
- Time-weighted average (TWA) 360 mg/m3 1985(r)
Belgium Threshold limit value (TLV)
- Time-weighted average (TWA) 180 mg/m3 1989(r)
Canada Threshold limit value (TLV)
- Time-weighted average (TWA) 180 mg/m3 1989
Finland Maximum permissible concentration (MPC)
- Time-weighted average (TWA) 180 mg/m3 1989(r)
- Short-term exposure limit (STEL) 530 mg/m3
Germany, Federal Maximum acceptable concentration (MAK)
Republic of - Time-weighted average (TWA) 180 mg/m3
- Short-term exposure limit (STEL) 360 mg/m3 1989(r)
- Biological tolerance value (BAT)
urine: hexane-2,5-dione plus 9 mg/litre
4,5-dihydroxy-2-hexanone, at end
of exposure or end of shift
Germany, Democratic Maximum acceptable concentration (MAC)
Republic of - Time-weighted average (TWA) 100 mg/m3
- Short-term exposure limit (STEL) 400 mg/m3 1988(r)
Italy Threshold limit value (TLV)
- Time-weighted average (TWA) 360 mg/m3 1985(r)
OCCUPATIONAL AIR EXPOSURE LIMIT VALUES (cont'd).
Country Exposure limit descriptiona Value Effectiveb date
Japan Maximum acceptable concentration (MAC)
- Time-weighted average (TWA) 141 mg/m3 1985
(skin absorption must also be considered)
Poland Maximum permissible concentration (MPC)
- Ceiling value (CLV) 400 mg/m3 1986(r)
Romania Maximum permissible concentration (MPC)
- Time-weighted average (TWA) 1200 mg/m3
- Ceiling value (CLV) 1500 mg/m3 1975(r)
Switzerland Maximum acceptable concentration (MAK)
- Time-weighted average (TWA) 180 mg/m3 1987
Sweden Hygienic limit value (HLV)
- Time-weighted average (TWA) 90 mg/m3
- Short-term exposure limit (STEL) 180 mg/m3 1990(n)
United Kingdom Guidance Limit (to be reviewed)
- Time-weighted average TWA) 360 mg/m3
- Short-term exposure limit (STEL) 450 mg/m3 1990(n)
(10-min)
OCCUPATIONAL AIR EXPOSURE LIMIT VALUES (cont'd).
Country Exposure limit descriptiona Value Effectiveb date
USA (ACGIH) Threshold limit value (TLV)
- Time-weighted average (TWA) 176 mg/m3 1989(r)
- Biological exposure index (BEI) 5 mg/litre
2,5-hexanedione in urine
(end of shift)
n-hexane in end-exhaled air 144 mg/m3
(during shift)
USA (OSHA) Permissible exposure limit (PEL) 1800 mg/m3 1987(r)
Yugoslavia Maximum permissible concentration (MAC)
- Time-weighted average (TWA) 1800 mg/m3 1971(r)
a TWA = a maximum mean exposure limit based on the period of a working day (generally 8 or 12 h).
STEL = a maximum concentration of exposure for a specified time duration (generally 15 or 30 min).
b n = Notified direct by country.
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biological exposure indices. Cincinnati, American Conference of
Governmental Industrial Hygienists.
ACGIH (1989) Threshold limit values and biological exposure indices
for 1989-1990. Cincinnati, American Conference of Governmental
Industrial Hygienists.
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Clinical toxicology of commercial products. 4th ed. Baltimore,
Maryland, The Williams and Wilkins Company.
IRPTC (1988) Data profile (legal file). Geneva, International
Register of Potentially Toxic Chemicals.
SAX, N.I. (1984) Dangerous properties of industrial materials. New
York, Van Nostrand Reinhold Company.
US NIOSH (1976) A guide to industrial respiratory protection.
3 Vol. Cincinnati, Ohio, US National Institute for Occupational Safety
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