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What's the Best Chemical Exposure Standard? OSHA or ACGIH?

Silas is a safety professional who obtained his Master of Science degree in safety.

Chemical hazards exist in many workplaces. Which standard should be used to determine reasonable exposure limits?

Chemical hazards exist in many workplaces. Which standard should be used to determine reasonable exposure limits?

How to Determine the Best Chemical Exposure Standard

We have heard about workplace accident statistics that pertain to chemical exposure. They seem to happen often. In these cases, who oversees safety in the workplace and provides oversight to protect you from harm?

Interestingly enough, all employers must offer safe work environments. In fact, the Occupational Safety and Health Administration (OSHA) established a law in 1970 to protect employees from injury (Fuller, 2015). That means employees must be protected from all hazards. This is significant news for the employee, although it's complicated for the employer.

Since OSHA opened its doors for business, workplace fatalities have dropped. Prior to the Occupational Safety and Health (OSH) Act of 1970, around 14,000 employee deaths per year resulted from unsafe working conditions. After the OSH Act went into effect, accidents diminished as employers worked to give employees safer work environments.

Since the 1970 law was enacted, 130 million workers and over 7.2 million worksites have reported a decline in accidents. The reduction went from 11 serious injuries per 100 workers to 3.6 injuries for every 100 workers (OSHA, n.d.). This presented a large drop in worker injury. More attention is still necessary to continue reducing exposure by contending with outdated data.

This article provides information concerning the OSHA permissible exposure limits (PELs) and the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit values (TLVs). Both entities develop limitations to protect workers from toxic chemicals. Having two limitation standards is important, but the two standards do differ from one another. So is one is better than the other? How can workplaces best follow OSHA standards?

OSHA's Outdated Limitations

OSHA has not updated many of its limitations, while other agencies have provided updates to the chemical hazard limitations and defined other exposure levels (Fuller, 2015). While many of the updates developed by other organizations exist (consensus standards, guidelines, and best practices), OSHA has not adopted many consensus standards, and this presents a concern from a chemical exposure standpoint. The concern involves outdated OSHA limitations that may or may not protect workers despite the fact that the OSH Act mandates the need by law.

The issue relates to OSHA's outdated standards directed by law, and the voluntary consensus standards are normally developed through other organizations. The other organizations present best practices as non-mandatory guidance. How does an organization follow the law and protect the worker with outdated information? We’ll discuss this later in the section titled "Deciding Which Exposure Limitation to Use."

OSHA Requires Compliance With Outdated Chemical Limitations

OSHA requires organizations to reduce risk by selecting standards below the established exposure limitations. The established PELs developed decades ago include less hazard information regarding acute and chronic risk. This suggests that a sample result that falls below the PEL is an acceptable risk. However, without updates to the PEL from the 1970s (and with no changes to information), worker health and wellbeing might be affected in an industrial organization. This suggests new standards are necessary to compare against the OSHA limitations developed years ago.

American Conference of Governmental Industrial Hygienists (ACGIH)

The American Conference of Governmental Industrial Hygienists (ACGIH) is a not-for-profit, nongovernmental organization. The ACGIH has established OELs that are health-based guidelines (ACGIH, n.d.). This means that the ACGIH can set or reduce their guideline limitation based on scientific research without considering the feasibility of employers using the OSHA OELs. They revise the guidelines after analyzing data. This has resulted in many threshold limit values (TLVs) being lower than the corresponding OSHA PELs. It is not unlikely to find a TLV below the corresponding OSHA PEL. This results from findings from research conducted years after the OSHA PEL.

How can we best decide which exposure limits to follow?

How can we best decide which exposure limits to follow?

Deciding Which Exposure Limitation to Use

How does the industrial hygienist decide which OEL to compare their results with? The first step includes reviewing the organization’s policy. Some organizations have a policy that they use only the binding OSHA PELs. Here, the decision to use the OSHA PEL as the only means of compliance with the law limits the protection of personnel with updated exposure limitations.

Other organizations develop OELs, and safety professionals use the most conservative limit. As a safety professional, I think this solution is the best choice. Discussing the chemical requirements and industrial hygiene best practices is the best choice. Best practices dictate that you use the most conservative OEL available.

Sometimes, the most tiresome job an industrial hygienist has is convincing management of the benefits of using a TLV instead of a PEL. Use the ACGIH best practices that are lower than the OSHA PEL figures. This presents a win, as the ACGIH TLVs are often less than the OSHA PEL numbers.

Another variable to consider when comparing sample results to OELs is the inherent error presented in the sample results. Because an error in the sample result presents itself, when you receive sample results that align with the published OEL, you cannot be sure that the actual exposure exceeds the OEL. An IH needs to take multiple samples and then do a statistical analysis of the results. This presents the best choice, but funding may present itself as a limitation.

Let's look at an example involving paint chemicals.

Let's look at an example involving paint chemicals.

Paint Vapor Example

Each vapor sample taken from the paint booth section fell below the OSHA and above the ACGIH exposure limit. This suggests that the controls are effective to protect the workers who do company paint tasks and exceed the OSHA standard. The results should exceed the ACGIH exposure limits.

Here, the company has complied with the OSHA requirement, but does this suggest the company has provided the employee with a safe and healthful work environment? We have to consider the OSHA limitations developed from the 1960s and 1970s. While the risk seems to be at an acceptable level, the ACGIH suggests otherwise. In this case, vapor results associated with toluene, 1, 2, 4 trimethylbenzene, and xylene risk need attention.

Paint Vapor Results

PPM = Parts Per Million.

HazardExposure LimitationsTest Results

1, 2, 4, Trimehtylbenezene

OSHA, Not Applicate. , ... 25 ppm, ACGIH TLV

26 ppm


200 ppm, OSHA TWA ...50 ppm, ACGIH 8-hour

100 ppm


100 ppm, OSHA TWA ..100ppm, ACGIH TWA

75 ppm

1, 2, 4, Trimthylbenezene

Vapor created by 1, 2, 4 trimethylbenezene irritates the nose, throat, and lungs, causing coughing, nausea, and shortness of breath (NIOSH, 2019). Other symptoms include problems with muscle control, anxiety, and confusion. The OSHA limitation does not exist, although the ACGIH specifies 25 parts per million (PPM). Since the result of 26 PPM exceeded the ACGIH limitation, the exposure hazards is unacceptable.


Toluene causes irritation of the eyes and nose, muscle fatigue, and tingling of the skin. Long-term exposure may cause liver and kidney damage (OSHA, 2019). The toluene sample result fell below the OSHA standard, although it exceeded the ACGIH limitation. Here, the company remains compliant with the OSHA mandatory exposure limitation. However, exceeding the ACGIH limitation raises concern and requires additional controls to lower the risk and protect the worker from the vapor hazard. Since they exceeded the ACGIH limitation, the risk is unacceptable.


Xylene is a flammable liquid that requires worker protection. This type of vapor absorbs through the lungs and through the skin. The test result fell below the OSHA and ACGIH limitations, and the risk is acceptable. However, during testing, errors may have occurred that require another viewpoint. For example, take 50% of the 100 PPM limitation and use the new number 50 PPM as the action level. Since 75 PPM from the test result exceeds the 50 PPM (50% of 100 PPM), consider the risk unacceptable.

Why Use 50% of the PPM?

Most occupational settings do not have hundreds of workers performing the same task. In several cases, only one individual may do a particular task and become exposed to a particular chemical hazard. This forces a decision concerning the exposure based on having a few samples.

To mitigate the chemical hazard, one approach is to compare the exposure to 50% of the OEL. For toxic and high-risk chemicals, OSHA recommends this approach to set up an action level. Action levels reduce the compound limitation for which OSHA has promulgated a chemical-specific standard (OSHA, 1970). An industrial hygienist should use 50% of the OEL for other chemical hazards as an action level. Thus, the worker has added protection.

The Takeaway

The industrial hygienist must decide concerning the sample results and OELs based on judgment and experience. Sometimes, this involves determining the toxicity of the compound. For example, if you have a sample result close to the OEL, and you know that the compound has a high toxicity, either acute or chronic, use 50% of the most conservative OEL available. Knowing the compound has a low toxicity, you may select the lowest OEL as the baseline without using the 50% method. Having an understanding of the acute and chronic toxicity presents a best standard among the OSHA and ACHIG limitations.


  • American Conference of Governmental Industrial Hygienists. (n.d.). TLV/BEI guidelines. Retrieved from
  • Fuller, T. P. (2015). Essentials of industrial hygiene. Itasca, IL: National Safety Council.
  • National Institute for Occupational Safety and Health. (2019). 1, 2, 4- Trimethylbenzene.
  • Occupational Safety and Health Administration. (n.d.). Timeline of OSHA’s 40 year history.
  • Occupational Safety and Health Administration. (1970). Occupational safety and health standards: Toxic and hazardous substances (Standard No. 1910.1025). Retrieved from regs/regulations/standardnumber/1910/1910.1025
  • Occupational Safety and Health Administration (2019). Toluene.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.