Global Occupational Exposure Limits for over 6,000 Specific Chemicals

  I. Introduction

The purpose of this book is to move the industrial and occupational hygiene field forward. This can best be accomplished if all interested parties have access to the global body of knowledge on the toxic effects of chemicals and occupational exposure limits (OELs.) Unfortunately, many industrial hygienists in the United States are only familiar with the 600 ACGIH TLVs®. Globally, there are now occupational exposure limits for over 5,000 different chemicals.

This book contains an initial chapter of text to acquaint the reader with some interesting historical perspectives on occupational hygiene and some of the current trends worldwide in chemical exposure control. The second chapter documents the various countries and agencies around the world that promulgate and enforce OELs. The tables of OELs are grouped into three sections in this book. The first section shows the OELs for chemicals with CAS numbers. The second table shows OELs for chemicals, mixtures or operations that do not have CAS numbers. The third table shows the minimum or “no risk” exposure standards for over 600 chemicals. Each of these tables is discussed in section F of this chapter.

This book does not include the wide variety of exposure limits that exist for physical agents, biological agents such as mold and bacteria, outdoor air quality or biological exposure indices. Nor does this book address the indoor air quality guidelines that exist for various groups of chemicals. These are all important concepts that can have a significant impact on health maintenance. However, the authors felt that these related issues could best be addressed in a separate document.

Since hygienists today often practice outside of the industrial environment, this book will use the more universal term “occupational hygienist” in lieu of the more cumbersome “industrial and occupational hygienist.”

A. Historical Perspective on Global Occupational Exposure Limits

Occupational exposure limits have rapidly developed in the world in the last 50 years.    However, prior to this recent history, a number of interesting insights into occupational hygiene and chemical exposure appear in the historical records. Most deal with lead, mercury, silica and asbestos. Isaac Newton is quoted as having said, "If I have seen further it is by standing on the shoulders of giants."   For those of us in the safety and health field, here are some of our giants:

· ca, 90-20 BC : Roman architect/engineer Marcus Vitruvius Pollio noted that lead workers had pale gray complexions. "In casting, the lead receives the current of air, [and] the fumes from it occupy the members of the body, and burning them thereon, rob the limbs of the virtues of the blood."

· ca. 23-79 AD : Roman citizen Pliny the Elder describes workers using sheep bladders as masks to protect themselves from cinnabar (mercury) dust and vapors.

· ca. 40-90 AD : Roman scholar Pedanius Dioscorides noted in his Materia Medica that eating lead would cause colic, paralysis and delirium.

· ca. 45-125 AD Roman priest Plutarch recommended that only criminal slaves be used in lead and mercury mines. "It was not just to expose non-criminals to the poisons of the mines."

· ca. 61-113 AD Roman scholar Pliny the Younger gave a fellow Roman the following advice: "Avoid buying slaves from the asbestos mines.   They only live 3 years."

· ca. 800 AD Russians spread the use of 'Bania' or bath houses (from the Romans) to promote cleanliness.

1400 years of "Dark Ages" in western culture.

· ca. 1556 : Georgius Bauer Agicola, author of De Re Metallica warned that heated rocks give off "fetid vapor" and said miners should not break rocks by fire inside a mine.   "Some mines are so dry that they are entirely devoid of water, and this dryness causes the workmen even greater harm, for the dust which is stirred and beaten up by digging penetrates into the windpipe and lungs, and produces difficulty in breathing, and the disease which the Greeks call [asthma] . If the dust has corrosive qualities, it eats away the lungs, and implants consumption in the body; hence in the mines of the Carpathian Mountains women are found who have married seven husbands, all of whom this terrible consumption has carried off to a premature death."

· 1567 : Philippus Aureolus Theophrastus Bombastus von Hohenheim-Paracelsus publishes that "All substances are poisons; there is none which is not a poison. The right dose differentiates a poison and a remedy."

· 1700 : Bernardo Ramazzini, "father" of occupational medicine in his De Morbis Artificum Diatria made a number of recommendations on welfare, hygiene, posture, ventilation and protective clothing which are still as valid today. The skin of miners "is apt to bear the same color as the metal" he said. Demons and ghosts are often found to disturb the miners.   At first tremors appear in the hands, soon they are paralyzed." Those gilding silver and copper objects through a mercury process, were also very susceptible.    "Very few of them reach old age, and even when they do not die young, their health is so terribly undermined, they pray for death."

· 1700s : Slovenia establishes one of the first   programs of occupational medicine for protecting worker health in the mercury mines of   Idria (Idrija.)

· ca. 1736 : The Legislature of   the State of Massachusetts passes an Act prohibiting the Use of lead in whiskey stills and worms after a number of fatalities occurred from drinking alcohol from leaded stills.

· 1767 :   In France, La Charite, a hospital, publishes a pamphlet listing the trades of Plumbers, Glasiers, Painters, who were exposed to lead, claiming they can cure the malady.

· 1775s : In England, Percival Pott identifies chimney sweep exposure to soot as cause of nasal and scrotal cancer.

· 1779 :   German physician Johann Peter Frank (1745-1821) recommends,   "A Complete System of Medical Policy advocating governmental responsibility for clean water, sewage systems, garbage disposal, food inspection and industrial health."

· 1786 : American statesman Benjamin Franklin's wrote a letter to Benjamin Vaughan expressing his concern about lead poisoning in the printing trades and from drinking rainwater from leaded roofs.   Franklin stated that he had the same pains in his hands as reported by other printers who handled lead type "giving them Dry Bellyach and loss of the use of their limbs."   Franklin further describes lead ingestion risks as follows, "Particles of the Metal swallowed with food by slovenly workmen, who went to their meals after handling the metal without well-washing their fingers, so that some of the metalline particles were taken off by their bread and eaten with it."

· 1801 :   In England, Miller publishes "New Diseases in London."   Discusses how mercury exposure to habidatures causes madness, painter's use of white lead leads to nerve damage, and how "abusers" of mercury develop kidney disease.   He recommends establishment of public health and bath houses, similar to Russia and other countries, to limit the spread of disease.

· 1831 :   Charles Thackrah publishes " The Effects of the Principal Arts, Trades, and Professions and of Civic States and Habits of Living on Health and Longevity. " He was the first physician in the English-speaking world to establish the practice of industrial medicine.   He wrote that glazers should avoid dipping their hands into lead glaze mix, or even better, that something only slightly more expensive could be substituted. "Surely humanity forbids that the health of workmen, and that of the poor at large, should be sacrificed to the saving of halfpence in the price of pots. Evils are suffered to exist even when the means of correction are known and easily applied. Thoughtlessness or apathy is the only obstacle to success."

· 1837 : Benjamin McCready publishes "On the Influence of Trade, Professions, and Occupations in the Unites States in the Production of Disease. "

· 1840 :   France issued a policy which discouraged the use of lead as a pigment in paint.

· 1849 :   In Germany, Peterkoffer proposes first known exposure standard for carbon dioxide of 1,000 ppm.

· 1860 :   In England, Moran published ventilation standards for various occupancies.

· 1866 :   German pathologist Friedrich Albert von Zenker proposed the term pneumoconiosis for lung disease related to occupational exposures to mineral dusts.

· 1870 :   Visconti gives silicosis its name.   He describes autopsying lungs with a knife like cutting through sand.

· 1870 :   Germany banned the manufacture of lead paint pigments after concluding it was too dangerous to manufacture.

· 1874   : English Army Surgeon F. deChamont conducts first indoor air quality survey relating five levels of symptoms to indoor carbon dioxide concentrations.   He proposes a carbon dioxide IAQ standard of 200 ppm above outdoor levels, approximately 500 ppm.

· 1875 :   In England, a bill passes preventing employing children as chimney sweeps.

· 1833 :   In England, British Factories Act required dilution ventilation of dangerous trades.

· 1883 :   In Germany, Max Gruber, of the Hygienic Institute at Munich proposes the first carbon monoxide standard of 200 ppm.

· 1883 :   England passes the Prevention of Lead Poisoning Act.

· 1886 :   Germany publishes the first occupational exposure limit value for carbon monoxide

· 1887 :   In England, Carnelley, Anderson and Haldane propose "air purity" standards for carbon dioxide, particulates, organic matter, mold and bacteria.

· 1898 : In England, Lady Inspectors of Factories were among the first to note the injurious effects of asbestos. One of them observed "the sharp, glass-like, jagged nature of the particles." Others noted the way in which asbestos, by fracturing longitudinally, seemed able to produce fibres endlessly--a process known as "silking out."

· 1906 : The first documented case of an asbestos-related death was reported in 1906 when the autopsy of an asbestos worker revealed lung fibrosis .

• 1912 : Kobert (Germany) published a list of acute exposure limits for 20 substances. The table on the following page is translated from the German document titled “Small amounts of hazardous industrial gases, which are toxic, which can be endured because of the amounts.” The data is adjusted to current units of ppm and mg/m3. The numbers are surprisingly high. Many of the repeated exposure levels “with minimal symptoms” are considered to be IDLH concentrations today!

Table 1 : Kobert’s Acute Chemical Concentrations for Various Exposure Times (ca. 1912)

For Human and Animals Rapid Death
0.5-1.0 hour exposure serious threat to life
0.5-1.0 hour without serious health effects
Repeated exposure minimal symptoms
1. Hydrogen chloride  
1,500-2,000 ppm
500-1,000 ppm
100 ppm
2. Sulfur dioxide  
4,000-5,000 ppm
500-2,000 ppm
200-300 ppm
3. Hydrogen cyanide
~3,000 ppm
1,200-1,500 ppm
500-600 ppm
200-400 ppm
4. Carbon dioxide
30 %
60-80,000 ppm
40-60,000 ppm
20-30,000 ppm
5. Ammonia  
250-450 ppm
300 ppm
100 ppm
6. Chlorine ~10,000 ppm
400-600 ppm
40 ppm
10 ppm
7. Bromine ~10,000 ppm
400-600 ppm
40 ppm
10 ppm
8. Iodine    
30 ppm
5-10 ppm
9. Phosphorus trichloride
3,500 mg/m3
3-500 mg/m3
10-20 mg/m3
4 mg/m3
10. Phosphine  
400-600 ppm
100-200 ppm
11. Hydrogen sulfide
10-20,000 ppm
5-7,000 ppm
2-3,000 ppm
1-1,500 ppm
12. Gasoline    
15-25,000 mg/m3
5-10,000 mg/m3
13. Benzene    
10-15,000 mg/m3
~5,000 mg/m3
14. Carbon disulfide  
10-12,000 mg/m3
2-3,000 mg/m3
1-1,200 mg/m3
15. Carbon tetrachloride
3-400,000 mg/m3
~150-200,000 mg/m3
~25-40,000 mg/m3
~10,000 mg/m3
16. Chloroform
3-400,000 mg/m3
70,000 mg/m3
25-30,000 mg/m3
~10,000 mg/m3
17. Carbon monoxide  
20-30,000 ppm
5-10,000 ppm
2,000 ppm
18. Aniline    
400-600 mg/m3
100-250 mg/m3
19. Toluidine    
400-600 mg/m3
100-250 mg/m3
20. Nitrobenzol    
1,000 mg/m3
200-400 mg/m3

· 1916 :   South Africa published an exposure limit for quartz at 8.5 mppcf (million particles per cubic foot.)

· 1917 :   U.S. Bureau of Mines established an initial limit for quartz at 10 mppcf.

· 1921 :   U.S. Bureau of Mines published exposure limits for 33 substances.

· 1927 :   International Critical Tables list exposure limits for 27 substances.  

· 1930 :   Russia published first MAC list with 30 chemicals.

· 1938 :   Germany published a list of about 100 OELs.

· 1941 :   American National Standards Institute (ANSI) Z-37 committee published the first U.S. exposure standard for carbon monoxide 100 ppm (58 years after Germany.)

· 1942 :   The Thresholds Committee of ACGIH published their first table of 63 exposure limits.

· 1943 :   Germany outlawed the use of asbestos for insulation in ships.

· 1949 :   India passed the Factories Act with their first table of exposure limits.

· 1950 :   The People's Republic of China published their first list of exposure standards.

· 1968 : U.S. includes ACGIH and ANSI exposure limits in the OSH Act passed in 1970.

· 1970's: Other countries adopt the latest version of the ACGIH TLVs® as the basis for their exposure standards in occupational safety and health laws.

· 1978 : U.S. Consumer Product Safety Commission outlawed lead in commercial paint (138 years after France.)

· 1980's : The concept of "Control Banding" to control chemical exposures is first proposed.

· 2000 : The Global Harmonized System for chemical labeling is introduced by the European Union (EU) to further chemical safety.

· 2002 :   The International Labor Organization (ILO) issues "Control Banding" Toolkit based on the Global Harmonized System for labeling to reduce chemical exposures worldwide.

· 2006 : Other than the United States and India, virtually all other countries update their OELs every 1 to 5 years.

1.   The Evolution of a More Responsible Attitude

As one can see from this chronology, many of the major occupational chemical exposure problems we recognize today have been know about for almost 2,000 years.   However, it has only been in the last 100-150 years or so that we have seen the development of the attitude that these occupational hazards are no longer acceptable.   This change in human culture started in earnest in Europe in the late 1880s.   It took another 50 years before this cultural change started to take hold in the U.S.   The following workers' compensation case from 1918 illustrates the latent attitude toward worker safety in the U.S. in the early 1900's.

Industrial Commission of Ohio v. Roth, 98 Ohio St. 34, 120 N.E. 172 (Oh. 1918)

In the fall of 1915, Edwin S. Roth was 18 years of age and was employed as a common laborer. He was requested by his employer, McFeeley Brothers, to paint a building that they were in the process of constructing. Roth attempted to comply with the request; however, since the weather was cold the paint would not flow from the brush. Not being a painter by trade, he requested assistance from the foreman who advised him that he should take the paint into a small designated building and heat it so that it would be warm enough to work with in cold weather. The building had little or no ventilation. Roth continued the process of heating the paint from time to time throughout that entire day and the next day. After the second day of working he became ill from inhaling the poisonous fumes and gases, and his condition worsened until he died 18 days later. Since lead poisoning was considered an usual and customary incident to someone who is a painter, compensation benefits were denied.

Today, such a case of lead poisoning would be covered under worker's compensation in virtually all countries with occupational safety and health legislation.  

Although South Africa published an exposure limit for quartz at 8.5 mppcf and the U.S. Bureau of Mines established an initial limit for quartz at 10 mppcf, the following travesty occurred in the late 1920's.   Union Carbide Company constructed the Hawk's Nest Tunnel in Gauley, West Virginia from 1927-1931. They ignored the US 1917 silica exposure standard, and allowed 2,000 miners to be grossly over exposed to over 98% pure silica quartz dust as they tunneled through a mountain. Over 400 workers died within 2 years. Almost all the remaining workers eventually died of silicosis.

The U.S. still has not caught up to most industrialized nations in the area of safety and health. As mentioned earlier, many countries outside the US have universal health care systems that treat both occupational and non-occupational diseases without direct cost to the patient.   Some of these countries use this medical treatment data in their computerized filing systems to track occupational disease incidence and help identify whether current occupational exposure limits are adequate. For example, Germany can combine the data in their national health system with a national occupational hygiene database (MEGA) that contains over 1,000,000 exposure records to assess the effectiveness of occupational exposure limits.

Internationally, occupational hygienists in other countries are aware of the existence of many standards in nations other than their own. They actively seek out this information through the International Labor Organization (ILO) or the European Union (EU.)  

2.   The ACGIH TLVs® as a Starting Point

A significant historical perspective is that of the ACGIH TLVs®. Early on, many developing countries started their hygiene standards by adopting the ACGIH TLVs® that were current at the time. Following this initial inception, these countries continue to use the ACGIH TLVs® a significant reference in updating their existing chemical exposure standards. The chemical exposure limits for almost 1 billion workers worldwide have been based upon the ACGIH TLVs®.

When the ACGIH was recently sued by some US based chemical manufacturers to stop implying that the TLVs® were exposure standards, this unjustified costly harassment litigation not only negative affected the health of US workers, it negatively affected the lives of a billion workers throughout the world.  

3.   Where We Go From Here

For a global economy to truly work, the workforce must be viewed a resource that should not be squandered. All participants should be using the same high standards. They all should be sharing their cumulative knowledge and experience in the area of worker safety and health for the betterment of all. The amount of accumulated research worldwide in the area of occupational exposure limits is truly gigantic. This reference book attempts to fill just one void by providing a comprehensive list of occupational exposure limits for chemicals.

Lastly, as shown above, the hazards of many chemicals have been known for thousands of years. Yet Benjamin Franklin said in 1786 , "you will observe with Concern how long a useful Truth may be known, and exist, before it is generally receiv'd and practis'd on."  

This reference book is intended to spread the "Truth" about the thousands of occupational chemical exposure limits so that they   "will be received and practiced on."

B. Trends in global Occupational exposure limits

The compilation and analysis of over 5,000 chemical exposure limits from numerous countries and organizations has revealed the following interesting variations and trends:

1. Other than the United States and India, most countries have OELs that date from 2003 or more recently.

2. All other G8 countries (Canada, France, Germany, Italy, Japan, Russia, and the United Kingdom) have active committees to study, develop and update their federally-enforceable OELs. The U.S. does not.

3. Germany has the most advanced system for developing OELs. They have an occupational hygiene database for storing all occupational hygiene data.   As of 2005, the database had over 1,000,000 data sets. This exposure data is used in conjunction with the national health care data system to look for health effects of chemicals in workers, and for other toxicological studies.

4. Most countries have 3 sets of OELs.   One for dusts, one for carcinogens and one for volatile or gaseous chemicals. Many countries also have separate standards for lead and asbestos.    OELs for physical hazards, noise, EM radiation, etc. are also separate sets of standards.

5. Russia has OELs for more substances than any other country, over 3,500, including approximately 100 OELs for specific species of mold and bacteria.

6. The US Department of Energy has the most OELs that are calculated based on animal toxicity. They also use data from the Russian OELs.

7. Singapore and the Philippines define STELs for all chemicals using a multiplier of the OEL when specific STELs have not been established.

8. The largest number of No Observable Effect Level (NOEL) standards have been set by theState of California and Santa Clara County, Callifornia.

9. Many of the OELs in other countries are lower than the current ACGIH TLVs®.

10. The OEL definition in a number of countries clearly state that OELs do not protect sensitive workers.

11 . The OELs in Russia are designated to minimize not only adverse health effects for the    majority of workers but also for the workers' future generations.  

12. Hungary has the most comprehensive OELs for dealing with carcinogens and mutagens.   They require a separate addition of these combined exposures.

13. Japan differentiates between inhalation sensitizers and skin sensitizers.

14. Venezuela requires an adjustment of the OELs based upon a work week that is longer than 40 hours, (in addition to the adjustments typically made for a work day that is longer than an 8 hours.)

15. Austria established OELs for highly-hazardous substances that averages employee exposures over a one year period.

16. New Zealand lists OELs for approximately 100 chemicals that they have not set standards for but are regulated by other countries.

17. The EU has established minimum uniform OEL standards for all EU countries. This includes standards for carcinogens. EU members must adopt these as minimum standards.

18. Some countries, such as New Zealand, adjust the OELs for respiration rate of the worker.

19. A number of countries adjust their OELs for altitude.

20. A number of countries adjust their OELs for standard temperature and pressure.

21. A number of countries automatically adjust OELs for a 48-hour work week.

22.   Of the 6,000+ OELs worldwide, over 4,200 are regulated in more than one country.

23.  A number of European countries prohibit the use of certain chemicals. These are listed as chemicals with an OEL of “0”  This is intended to mean that those chemicals are banned from use in their respective countries.  These factors are incorporated into the chemical tables A – C found later in this book as “minimum levels.”

C.   DEFAULT Occupational exposure limits - Control Banding

In the late 1980's, at a pharmaceutical safety meeting that included the safety directors of 15 of the largest integrated multi-national pharmaceutical companies, the issue of how to protect research and development scientists from the health effects of newer active pharmaceutical ingredients (APIs) was discussed. This occupational health challenge was identified because of repeated adverse health effect experiences in R&D staff   when handling newer   chemical entities

in process scale up to kilogram quantities. These problems occurred because OELs, a standard occupational hygiene tool, were unavailable for these new chemicals.

This dilemma arises when a new API is being developed and processed for which toxicity and potency data are not yet available to set OELs.   Employee exposures to working in chemical and pharmaceutical development operations such as filtering, drying, weighing, milling, blending and tablet and capsule manufacturing can be significant, especially if the compound is potent.   Many of these processes require "open" handling of powder and can release material into the air at concentrations of concern when the batch size approaches the kilogram scale. Pharmaceutical compounds range in potency from lower potency non-steroid, anti-inflammatory drugs to highly potent steroids, peptide hormones, cytotoxic drugs and prostaglandins.

i. Development of the Concept

Five companies volunteered to work on this problem and report possible solutions to the larger group of 15 companies.   Occupational health and safety professionals of Syntex, Merck, Abbott, Upjohn and Lilly agreed to meet quarterly to develop a way forward. The sub-group met over a two-year period. The initial concept that emerged was based on the four levels of biosafety control developed by the U.S. Centers for Disease Control (CDC) and the National Institutes of Health (NIH) for handling pathogenic viruses and bacteria. The microorganisms were categorized based on an ascending order of pathogenicity from Biosafety Level 1 (least pathogenic) to Biosafety Level 4 (most pathogenic.) Parallel category levels were proposed for drugs, ranging from working on the open bench with good laboratory techniques to working inside air supplied protective suits.

The idea that pharmaceutical compounds could be put into such categories was based on the previous experience of drug products that were well known and studied. The toxicologists in the group described the characteristics of drugs in a matrix of increasing health effect severity and the industrial hygienists linked these to work environments where air monitoring studies supported operations that were considered safe and acceptable.  

This has been described as the "hand-in-glove" system, where compound characteristics (the hand) are matched to safe work environment descriptors (the glove.) An additional concept utilized by safety professionals worldwide is to assume something is hazardous until it is demonstrated not to be (i.e. to err on the side of conservatism.) This concept resulted in establishment of a "default" category or band for substances that were brand new or novel and for which very little toxicological information was known.

For example, open handling of powder can release milligrams of material per cubic meter of air. A chemical bench hood may control airborne powder down to a hundred micrograms per cubic meter of air. A closed transfer device with special valves may control down to a microgram per cubic meter of air and an isolator glovebox may control down to several nanograms per cubic meter of air. During this phase of concept development, variations on this theme were considered. Companies evaluated three, four and five tiered systems. However, the use of only 4 or 5 categories faded quickly when it became clear that equipment, layout, construction and procedures differed significantly from company to company

To date, there are at least sixteen variations on this theme within the original 15 pharmaceutical companies. In addition, numerous other systems have evolved within contract manufacturers, biotechnology companies and generic pharmaceutical companies. Most systems are either four category systems or five category systems. (Naumann , B.D . , et al., "Performance-Based Exposure Control Limits for Pharmaceutical Active Ingredients," AIHA Journal, January 1996 p. 33-42.) The concept has been almost universally accepted and adopted throughout the pharmaceutical, and now biotechnology industry, in its various forms. The importance of the system has grown due to the rapid development of candidate drug substances that will require laboratory testing and the increasing trend toward higher potency drugs.

ii. Not a Replacement for Quantitative Risk Assessment

The pharmaceutical banding system was developed with the intent that health and safety professionals would apply sound judgment to particular situations using the system as a guide.   However, the use of such a system does not remove the requirement for quantitative risk assessment and good occupational hygiene practice.   Specifically, this means that pharmaceutical companies must still develop OELs and validated air monitoring methods to assess worker exposure and to prevent impacts to their health. As a perspective, some regulatory agencies in the EU will not accept the "banding control" approach by large chemical and pharmaceutical companies.   Proper OEL setting and measurement of worker exposures are the standard expectation of these agencies in companies where occupational heath resources should be available.   (Farris, J. P., A. W. Ader, R. H. Ku, "History, Implementation and Evolution of the Pharmaceutical Hazard Categorization and Control System", Chemistry Today, Vol. 24 nr 2, March/April 2006, 5-10.)

b. The Development of Control Banding for General Industry

Similarly, during the 1990s, a number of international conferences were held on the subject of controlling exposures for chemicals without OELs. Their concept of control banding included how the chemical was being used or handled in addition to its potential toxicological properties.   The International Labor Organization (ILO), the Health and Safety Executive (HSE) in the United Kingdom, the UN World Health Organization (WHO) and the US National Institute of Occupational Safety and Health (NIOSH) initiated this effort.   The use of this concept was designed for small employers who have barriers to assessing and managing chemical (and other) risks in the workplace due to a lack of expertise, technology, finances and time.

In 2000, the ILO developed a ToolKit for implementing "Control Banding" and issued it as a test program. From 2002 to 2005, it was developed in formative stages in 14 countries. (Argentina, Gambia, Thailand, Indonesia, Japan, China, Vietnam, Chile, Russia, Bulgaria, Yugoslavia, South Africa, India and Germany.)

The current version of the ILO Control Banding ToolKit is consistent with the EU Global Harmonized System (GHS) for Hazard Communication. This system has various "R" and "S" phrases to describe the hazards of various chemicals. There are approximately 100 "R" and "S" phrases. A discussion of these phrases is beyond the scope of this book.  

Below is a brief summary of the five steps in the ILO ToolKit to apply control banding to the use of chemicals. The complete ILO procedures can be found at:

i. Obtain the MSDS for the chemical and determine what GHS hazards are present. Classify the chemical as shown in Table 1.

Table 1. Control Banding Hazard Group Identification

Hazard Group

EU R-Phrases

GHS Hazard Classification



R36, R38, R65, R66

All dusts and vapours not allocated to another band

Acute toxicity (lethality), any route, class 5

Skin irritancy class 2 or 3

Eye irritancy class 2

All dusts and vapours not allocated to another band


R20/21/22, R40/20/21/22, R33, R67

Acute toxicity (lethality), any route, class 4

Acute toxicity (systemic), any route, class 2


R23/24/25, R34, R35, R37, R39/23/24/25, R41, R43, R48/20/21/22

Acute toxicity (lethality), any route, class 3

Acute toxicity (systemic), any route, class 1

Corrosivity, subclass 1A, 1B or 1C

Eye irritancy class 1

Respiratory system irritancy (GHS criteria to be agreed)

Skin sensitisation

Repeated exposure toxicity, any route, class 2


R48/23/24/25, R26/27/28, R39/26/27/28, R40 Carc. Cat. 3, R60, R61, R62, R63, R64

Acute toxicity (lethality), any route,

class 1 or 2

Carcinogenicity class 2

Repeated exposure toxicity, any route,

class 1

Reproductive toxicity class 1 or 2


R42, R45, R46, R49, R68

Mutagenicity class 1 or 2

Carcinogenicity class 1

Respiratory sensitisation


skin and eye contact

R21, R24, R27, R34, R35, R36, R38, R39/24, R39/27, R40/21, R41, R43, R48/21, R48/24, R66

Acute toxicity (lethality), dermal only,

class 1, 2, 3 or 4

Acute toxicity (systemic), dermal only,

class 1 or 2

Corrosivity, subclass 1A, 1B or 1C

Skin irritation class 2

Eye irritation class 1 or 2

Skin sensitisation

Repeated exposure toxicity, dermal only, class 1 or 2

ii. Determine the quantity of chemical in use or to be used as shown in Table 2.

Table 2. Quantity of Chemical in Use





Typically received in


Typically received in



Packets or bottles





Kegs or drums






Cubic metres


iii. Determine the chemicals ability to become airborne as in Table 3 .   (If a liquid is heated see ILO ToolKit volatilility determinazation graph.)

Table 3.   How Dusty or Volatile is the Chemical





Boiling point below 50 o C

Fine, light powders. When used, dust clouds can be seen to form and remain in the air for several minutes e.g. cement, carbon black, chalk dust.


Boiling point between 50 and 150 o C

Crystalline, granular solids. When used, dust is seen, but settles out quickly. Dust is left on surfaces after use e.g. soap powder.


Boiling point above 150 o C

Pellet like solids that don't break up. Little dust is seen during use e.g. PVC pellets, waxed flakes

iv. Determine the Control Approach Number from Table 4.

  Table 4. Control Approach Number Based on Amount Used, Volatility and Hazard Group

Amount used

Low dustiness or volatility

Medium volatility

Medium dustiness

High dustiness or volatility

Hazard group A
















Hazard group B
















Hazard group C
















Hazard group D
















Hazard group E

For all hazard group E, choose control approach 4

Hazard group S

For all hazard group S or Pesticides, add control approach 5

v. Retrieve the Review ILO Task Control Sheet Based on the Control Approach # from Table 4.

Table 5.   Control Bands for Exposures to Chemicals by Inhalation

Control Approach
Target Range of Exposure Concentration
Hazard Group
1 >1 to 10mg/m3 dust skin and eye irritants Use good industrial hygiene practice and general ventilation (See ILO Task control sheets 100 103).
2 >0.1 to 1 mg/m3 dust Harmful on single exposure Use local exhaust ventilation, (See ILO Task control sheets 200 - 221).

>0.01 to 0.1 mg/m3 dust
>0.5 to 5ppm vapor

Severely irritating and corrosive Enclose the process (See ILO Task control sheets 300 - 318).

<0.01 mg/m3 dust
<0.5 ppm vapor

Very toxic on single exposure, reproductive hazard Seek expert advice (See ILO Task control sheet 400).
5 additional skin and eye protection sensitizers, pesticides, corrosives PPE recommended by an Expert (See ILO Task Control sheets P100 - P104).

German studies of the use of control banding have shown that overall, it appears to work, but the margin of safety can be very small.

This book is intended to help reduce the situations where control banding is necessary and to provide some better perspective on when it can be used.


Most occupational exposure limits are based on human and/or animal toxicological data.   A number of countries use calculations to derive some of their occupational exposure limits.   The Philippines, Singapore, Germany and a few other countries define STELs as factors of their OELs without listing the STELs specifically in their standards.   For these countries, the calculated STELs are incorporated into the data used to generate the statistical tables listed in Chapters III-V of this book.

E. Definitions of the Various OEL s AND TERMS Listed in this Book

Below is a brief description of some of the OELs and terms listed in this book.

1.   AEGL - Acute Exposure Guideline Levels are exposure limits applicable to rare, such as once-in-a-lifetime, exposures to airborne chemicals.   They are intended to describe the risk to humans resulting from chemical exposure at the AEGL. AEGLs are developed by a joint committee with representatives from both government and corporations in the United States.   This is known as the National Advisory Committee for AEGLs.   They are developing these guidelines to assist both national and local emergency response authorities who respond to chemical releases or spill emergencies. (For a more detailed discussion, see Chapter II, Section B.1.)

2.   CL - Ceiling Limit is an exposure level not to exceeded "even for an instant."   However, in practicality, analytical instrumentation takes some time to collect a sample.   Actual application times for the instruments for measuring these standards range from 30 seconds to 5 minutes.   Therefore, they are actually not instantaneous standards.

3.   ERPG - Emergency Response Planning Guidelines emergency chemical exposure limits for chemicals developed by the AIHA ERPG committee and published by AIHA. (For a more detailed discussion, see Chapter II, Section B.3.)

4.   HBEL - Health-Based Exposure Limit established by the Santa Clara County, California Center for Occupational Safety and Health (For a more detailed discussion, see Chapter II, Section B.5.)

5.   IDLH - Immediately Dangerous to Life and Health concentration of a chemical in air that can cause a life threatening or permanently damaging health effect in 15 minutes or less. (For a more detailed discussion, see Chapter II, Section B.6.)

6.   MEL - Maximum Exposure Limits are health-based standards promulgated in the United Kingdom. They consider economic limitation in the cost of controlling exposures. MELs are only allowed for those substances for which the effects of overexposure are minor, such as irritation. (For a more detailed discussion, see Chapter II, Section B.47.)

7.   MRL - Minimal Risk Level to health from long term, continuous 24-hour exposure for 70 years developed by the Agency for Toxic Substances Disease Registry (ATSDR) for assessing health risk to communities from chemical exposure from landfills and hazardous waste sites. (For a more detailed discussion, see Chapter II, Section B.1.)

8.   NCEL - New Chemical Exposure Limits established by the EPA for new substances. The NCEL is an interim level determined by the EPA based on the limited information available to the Agency at the time of development of the NCEL. (For a more detailed discussion, see Chapter II, Section B.7.)

9.   NOEL - No Observable Effect Levels for reproductive hazards established by the State of California Proposition 65. (For a more detailed discussion, see Chapter II. Section B.4.)

10.   NOAEL - No Observable Adverse Effect Level

11.   NSRL - No Significant Risk Levels for carcinogens established by the State of California Proposition 65. (For a more detailed discussion, see Chapter II, Section B.4.)

12. OEL - Occupational Exposure Limit.   This term generally refers to 8-hour time-weighted average (TWA) exposure levels by various countries. However, in this reference book, this term is sometimes used generically to include TWAs, STELs and CLs.

13. REL - Recommended Exposure Limits established by US NIOSH for updating the PEL standards. (For a more detailed discussion, see Chapter II, Section B.10.)

14. STEL - Short Term Exposure Limit usually measured over a 15-minute period.

15. TEEL - Temporary Emergency Exposure Limit established by the US Department of Energy (DOE.) They range from TEEL-0 to TEEL-3 and correlate to OELs, STELs, CLs and IDLHs respectively. (For a more detailed discussion, see Chapter II, Section B.6.)

16. TLV® - Threshold Limit Value established by the American Conference of Governmental Industrial Hygienists (ACGIH.) They include TWAs, STELs and CLs. (For a more detailed discussion, see Chapter II, Section B.2.)

17. WEELs - Workplace Environmental Exposure Limits set by the American Industrial Hygiene Association (AIHA.) Each WEEL guideline represents the workplace exposure levels to which it is believed nearly all individuals could be exposed repeatedly without experiencing adverse health effects. (For a more detailed discussion, see Chapter II, Section B.3.)

18.   WOE - Weight of Evidence. A calculation of the number of countries and organizations that have a standard for that specific type of chemical exposure limit. A higher weight of evidence indicates that more toxicologists from around the world have evaluated the health effects of that chemical. There are WOEs for OELs, STELs, and CLs.

F.   Organization of the Global Occupational Exposure Limits in this Book

The tables of OELs are grouped into three sections in this book.   Chapters III-V consist of tables of OEL standards for over 5,000 specific chemicals. This includes 8-hour TWAs, STELs, CLs, IDLHs and a variety of minimum risk exposure limits.   The tables list the lowest standard for each chemical (MIN), the highest standard for each chemical (MAX), the median or most common standard (MEDIAN) and in some cases, the weight of evidence (WOE.)

1.   Chapter III - Table A

Table A lists the OELs, STELs, CLs, IDLHs and TEELs for chemicals for which a CAS number was available on the internet or are shown in the individual country OEL list.   The table is organized by the chemical's CAS number. They are listed by CAS number since the names of chemicals in the various countries differ due to differences in both language and chemical science nomenclature. The use of CAS numbers allows the reader to look up the exposure limits for a chemical without the need for translation of the chemical name into English.

a.   OELs

For each chemical, the full-shift OEL table shows the:

  ·   lowest OEL of any country,

  ·   median of the OEL for all the countries that have a standard,

  ·   maximum OEL of any country,

  ·   TEEL-O for that chemical, if it exists, and

  ·   weight of evidence (WOE) - number of countries and organizations that regulate that


b.   STELs

For chemicals with STELs, the table shows the:

  ·   lowest STEL of any country,

  ·   median of the STEL for all the countries that have standards,

  ·   maximum STEL of any country, and

  ·   TEEL-1 for that chemical, if it exists, and

  ·   weight of evidence (WOE) - number of countries and organizations that regulate that


c.   CLs

For chemicals with Ceiling Limits, the table shows the:

  ·   lowest ceiling limit of any country,

  ·   median of the ceiling limit for all the countries that have standards,

  ·   maximum ceiling limit of any country,

  ·   TEEL-2 for that chemical, if it exists, and

  ·   weight of evidence (WOE) - number of countries and organizations that regulate that


d.   IDLHs

For chemicals with IDLH limits, the table shows the:

  · DLH concentration, and

  · TEEL-3 for that chemical, if it exists.

2.   Chapter IV - Table B

The second table shows OELs for chemicals, mixtures or operations that do not have CAS numbers.   The names are listed alphabetically based on the International Union of Pure and Applied Chemistry (IUPAC) name, when available.   If the IUPAC name was not available, the common chemical used in most OEL standards was selected. In some cases, where the English translation was not available, the substance names are listed in the native language of the regulating country.

The OELs, STELs, CLs, TEELs and IDLHs shown in Table B follow the same format as Table A and show the same statistical information.

3.   Chapter V - Table C

The third table shows the minimal or “no risk” exposure standards for more than 1,670 chemicals.  Table C lists eleven different “no risk” exposure standards. These standards are designed to protect the general public over a lifetime of exposure at or below these levels.  The detailed description of each standard is discussed later in this chapter except for the Russian air quality standards. The Russian air quality standards are established by

These levels are recommended to be used to assess risk levels in indoor air quality investigations.  In fact, the Michigan and ATSDR standards were specifically developed for this purpose. The standards are grouped into three classes.  These are:

Non-Cancer Health Based “No” Risk Levels (10-6 risk)
•  Michigan ITSL Initial Threshold Screening Level in mg/m3.
•  HBEL Inhalation Insignificant Risk Level in mg/m3.
•  Russian Air Quality Standards
• ATSDR Chronic Inhalation Minimal Risk Level in mg/day.
• ATSDR Chronic Ingestion (Oral) Minimal Risk Level in mg/day.  (This also includes the
       WHO Joint Expert Committee on Food Additives – Mycotoxins in mg/day.)

Cancer Based “No” Risk Levels (10-6 risk)
•  Michigan IRSL Initial Risk Screening Level in mg/m3.
•  HEBL Cancer Inhalation Insignificant Risk Level in mg/m3.
•  PROP 65 Cancer No Significant Risk Level for Inhalation in mg/day.
•  PROP 65 Cancer No Significant Risk Level for Ingestion (Oral) in mg/day.

Reproductive “No” Risk Levels (10-6 risk)
•  PROP 65 Reproductive No Observable Effect Level for Ingestion (Oral) in mg/day.
•  PROP 65 Reproductive No Observable Effect Level for Inhalation in mg/day.

In using the mg/day inhalation numbers to evaluate exposure levels, one needs to know how long the exposure occurs. If the exposure only occurs for 24 hours, one divides this number by 20 to convert this level to mg/m 3 level. This conversion factor is based on an average adult ventilation   rate of 20 m 3 per day.    For children and strenuous activities for adults, a different ventilation rate should be used.

There is no direct conversion for ingestion or oral exposure levels to airborne levels.   For some chemicals the oral level in mg/day is higher than the inhalation level, for others it is lower.

G.   Interpretation of Exposure Data Using These Tables

If more detailed information on a chemical is required, such as in an expert testimony case, each specific country's standard for a particular chemical can be obtained in the form a Global Occupational Exposure Limit Data Sheet (GOELDS.)   (See the last two pages of this book.)

1. What do OELs Really Mean? Application of OELs

In using an OEL to evaluate a person's exposure to a chemical, it should always be kept in mind that they are not the difference between safe and unsafe exposure levels.   They are do not represent a toxic "threshold."    What this means is that many OELs are based on overt physical symptoms such as irritation and do not reflect the point at which no toxic effects will occur whatsoever - what is called a toxic end point.   

This is best illustrated by an example. The current exposure limit for lead is based on a measuring a toxic end point of blood lead levels and neurologic effects.   These effects occur well before any obvious physical symptoms are apparent. Clearly, the lead exposure standard is based on a measurable, toxic end point.  

A second example is the ethylene oxide (EtO) exposure standard. It is based on the measurement of the Sister Chromatid Exchange (SCE) increases in white blood cells. This measures the amount of mutation that occurs in DNA. At EtO exposure levels below 1 ppm, the SCE rate is not significantly different than normal levels of mutation that occur in cells. This toxic end point is again well below any visible health effects, such as irritation, which would occur at over 1,000 ppm.

A third example is the asbestos standard for amphibole fibers. This standard of 0.1 f/cc is well below any level where irritation or any other symptom would occur. This standard is based on a a possible cancer health effect that may occur 40 years later.   Clearly, a toxic end point.

On the other hand, the exposure standard for hydrochloric acid is based on irritation. The toxic endpoint for long-term exposure, if any, is not used as the basis for the OEL. A second example of a standard that is not based on a toxic end point is the exposure standard for xylene.   This standard is also based mostly on irritation. The toxic end point for the neurologic and liver effects for this chemical have not necessarily been reflected in the OEL.   This has been justified because the person detoxifies from the exposure during non-working periods.

Unfortunately, there is no exact way to distinguish which OELs are based on toxic end points and which are not.    Only a thorough review of the toxicological literature can provide some answer to this question.  

This book makes an effort to provide some perspective and interpretation of the differing toxicological bases for each of the OELs.   This is done by providing data in the minimum risk data table, Table C which includes NOELs.   If OELs are close to the NOELs, then the OELs are probably established near the toxic end point.   On the other hand, if there is a significant difference between the NOEL and the OEL, then the OEL is probably established using other criteria.

Further, the TEELs are shown separately from the OELs.   This is because most TEELs are based on toxicology modeling and are independent of potential political and special interest bias.   Again, if an OEL is similar to the TEEL, then the OEL is probably more toxicity-based than just acute symptom-based.

What this means is that if an employee's exposure level is near an OEL that is far above the TEEL or NOEL, then this situation is probably more critical and health effects are more likely than in a situation where the OEL, TEEL and NOEL are very similar and the exposure level is near or below these numbers.

5. Differences in the Sexes

Historically, many studies on the effects of chemical exposure were performed using young men. In 1994, the U.S. National Cancer Institute (Potern et al. 1994) evaluated the data available from occupational health studies to determine the impact of chemicals on women. They found that women were often excluded from these types of studies.   Further, when women were included, their data were often not analyzed or analyzed less rigorously.   This means that information on the effects of chemicals on women is limited.

Currently, no countries differentiate the application of the OELs based on gender. However, the occupational hygienists should be aware that there is a potential for varying health effects for women.   Women breathe more frequently than men do, so they inhale larger amounts of chemicals for their body weight than men do. Women also typically have more body fat and can store larger amounts of toxic chemicals in their body.    This may be why they also take longer to detoxify from a chemical exposure. Another complicating factor is that women can also become pregnant and expose the fetus to certain hazardous chemicals.   This can result in developmental abnormalities.  

An analysis of the limited existing toxicological data suggests that there are more than 200 chemicals for which important toxicity differences have been observed between male and female experimental animals. (Calabrese, E. J., "Sex Differences in Susceptibility to Toxic Industrial Chemicals," Brit J. Ind. Med. 43, 577-579, 1986.)

Another well-documented difference between men and women is that odor thresholds for women vary with hormone levels and can be much lower than odor thresholds in men. It is, therefore, not uncommon to find more women complaining about odors in the workplace than men. As an extreme example of this, morning sickness or aversion to certain foods during pregnancy is partially due to a heightened sense of smell.

6. Employees on Medications

The use of medications for various reasons is more commonplace today than in recent years.   This is because people have more access to health care worldwide and there are more types of medications for various health problems than ever before.   This is even more pronounced in older workers.   

However, every medication must be detoxified by the body. What this means is that the daily or frequently use of medications can affect and limit the body's ability to detoxify chemicals introduced into the body through work place exposures.

The occupational hygienist should consider evaluating workplace exposures in light of this potential health impact.   

7. Adjustments for Extended Shifts   (By Tony Havics, CHMM, CIH, PE)

Employees in a number of countries and companies work longer than 8-hour shifts. Full-shift OELs are typically based on an 8-hour time-weighted average (TWA) exposure. To reflect this longer exposure time, many countries require a linear reduction in the OELs, so that the total daily or shift exposure dose is still equivalent to the 8-hour TWA OEL.   For example, a 9-hour workday, which is 12.5% longer than an 8-hour workday (9/8 =1.25) requires a 12.5% reduction in the OEL time-weight average concentration in the workplace. This adjustment method is mostly used because of its simplicity. However, one country, Venezuela requires that the method or model for adjusting OELs be approved by an occupational hygienist.  

The question is whether this simple linear adjustment to the OEL is adequate to protect the worker.   There are three methods or models that have been developed or proposed for making such adjustments to the OELs.

a.   The S-B Model

The first of these models was developed by Scala and Brief of Exxon Corporation in 1975. This model noted that in a 12-hour workday, a person would be exposed to 50% more chemical, but would also have a corresponding diminished recovery or detoxification time. This is shown in the following formula:

                                OEL (adjusted) = OEL (8 hour)   x RF (reduction factor)

RF   =    8     x     (24 - H)        where H = the number of hours worked

                                               H                  16

Examples using this model are shown in the table below.

b. The Physiological Based or Pharmacokinetic (PB-PK) Model

The second of these models adjusts the OEL based on the estimated biological half-life of a substance or its metabolite in the body.   This model tends to be less conservative than the S-B model. Some pharmacokinetic models include the Mason and Dershin, Hickey and Reist, and Roach and Verg-Pederson models.   The equations for these models are quite complex and require considerable individual discussion.   Hence, they are beyond the scope of this book. However, a computational example is shown in the table below as the PB-PK model.

            Table 6 : Comparison of OEL Adjustment Factors for Extended Work Schedules

Work Schedule

Linear Model

S - B Model

PB - PK Model

8 hours for 5 days/week




10 hours for 4 days/week




12 hours for 3 days/week




12 hour alternating 3 and 4 days/week





Certified Industrial Hygienists (CIHs), Registered Professional Industrial Hygienists, (RPIHs), Certified Safety Professionals (CSPs), Registered Occupational Hygienists (ROHs) in Canada,   and other safety and health professionals face a new potential liability risk for the use of only OSHA PELs, ACGIH TLVs®, and local exposure standards.   This is especially true for consultants.

There are two main reasons for this increase in potential liability for registered and certified professionals.   First, most organizations that register or certify professionals have a Code of Ethics that requires the individual to practice only in areas where they are competent.   Certainly, if one does not know that a specific exposure limit has been established for a chemical elsewhere in the world, whether or not their country regulates that chemical, they are not truly an expert on that chemical.   Second, the various professional registrations and certifications require continuing education credits to maintain their certifications.   Clearly, knowing the global toxicological data and exposure limits for a chemical is fundamental to continuing education about chemical safety.  

Global toxicological knowledge is also clearly acknowledged on many Material Safety Data Sheets available in the US.   Also, many of the roughly 600 NIOSH Registry of Toxic Effects of Chemical Substances (RTECS) information sheets list many of the chemical exposure limits from other countries.   If corporations list this information to minimize their liability and RTECS lists this information indicating it is important, then why would ignorance of other country's OELs standards be acceptable for registered or certified professionals?

However, some industrial hygienists in the US choose to ignore this information because "it is not required by law."    For example, if a worker in the US develops a disease while being exposed to a chemical at an outdated exposure limit, the CIH could find himself or herself being sued for negligence.   The CIH is considered to be a knowledgeable expert, but probably did not warn the employer that the exposure limits used in other industrialized countries are typically lower, are based on more recent toxicology data and are kept up-to-date.   Interestingly, the ACGIH has already been sued using this legal theory. The case was subsequently settled.   Currently, plaintiffs in manganese toxicity cases in the US are using this same legal theory.

Canada provides the best real world example of this situation.   In the 2000 revised Canadian Safety and Health statues it states:

2(1) Every employer shall ensure, as far as it is reasonably practicable for the employer to do so,

      (a) the health and safety of

• (i) workers engaged in the work of that employer, and

• (ii) those workers not engaged in the work of that employer but present at the work site at which that work is being carried out, and

     (b) that the workers engaged in the work of that employer are aware of their responsibilities and duties under this Act and the regulations.

By including the words "reasonably practicable", legislators have made the Occupational Health and Safety Act a legal question of "strict liability" that can make supervisors, safety managers and occupational hygienists criminally liable for worker injuries. This revised statute now require due diligence on the part of safety practitioners.   Due diligence is the level of judgment, care, prudence, determination, and activity that a person would reasonably be expected to do under particular circumstances. If one exercises due diligence, it can be used as a defense argument.   An occupational hygienist who practices in Canada with outdated information or without informing the employer of more stringent standards elsewhere in the world may not be practicing due diligence and could be at increased risk of regulatory liability.

II.   Background Information on Occupational Exposure Limits BY COUNTRY AND ORGANIZATION

This chapter describes how the occupational exposure limits are established by various countries and organizations. Some industrial hygienists in the US are under the impression that other countries use the ACGIH TLVs® as their sole reference for industrial toxicology.   However, in many countries, there are highly-experienced toxicologists who also review available literature and set exposure standards based on this information.  

Therefore, it is not surprising that there are also some variations in the intent and scope of the occupational exposure limits established by other countries.   These may include a protection against cancer, reproductive health effects, material health impairment or other factors. In one case, the governing bodies take into account economic factors in establishing a feasible exposure limit (e.g. the MEL in England.)

One very interesting set of limits in this book is the "health-based exposure limits" (or HBELs) promulgated by the Santa Clara Center for Occupational Health and Safety in Santa Clara, California. These standards evaluate chemical exposure risks for the general public and are designed to be as close to a zero health risk as possible.   Although they are technically not occupational exposure limits, they can offer a broader perspective on workplace and environmental risk factors. They may also be particularly useful when interpreting data from residential or commercial indoor air quality studies.

Section A of this chapter discusses the available information on standard-setting bodies in each country for which occupational exposure limits are known to exist.   This information is provided for occupational hygienists who wish to pursue additional information from a particular country of interest.   We also hope it will allow occupational hygienists to gain a greater appreciation for the immense efforts of safety and health professionals around the world.

Section B of this chapter sites similar information for other organizations that promulgate OELs or related, environmental exposure limits.