Written by Brenda A. Tolson-Markas, CIH, CSP, ASP, CSSS, CSSM and Member of ACOEM.

Benzene Introduction

Benzene is found in the air from emissions from burning coal and oil, gasoline service stations, and motor vehicle exhaust. Acute exposure, which is a short term period of inhalation exposure of humans to benzene, may cause drowsiness, dizziness, headaches, as well as eye, skin, and respiratory tract irritation, and at high levels, unconsciousness. Chronic exposure, which is over a long period of inhalation exposure has caused various disorders in the blood, including reduced numbers of red blood cells and aplastic anemia, in occupational settings.   Reproductive effects have been reported for women exposed by inhalation to high levels, and adverse effects on the developing fetus have been observed in animal tests (“EPA and Benzene”, n.d.). Increased incidences of leukemia (cancer of the tissues that forms white blood cells) have been observed in humans occupationally exposed to benzene. EPA, OSHA, NIOSH, ACGIH, and WHO have classified benzene as a known human carcinogen for all routes of exposure.

Protecting Human Health along with Air, Water, Soil, and Food

The federal government develops regulations and recommendations to protect public health. The Regulations can be enforced by law. The EPA, the Occupational Safety and Health Administration (OSHA), and the Food and Drug Administration (FDA) are federal agencies that develop regulations for toxic substances. Recommendations provide valuable guidelines to protect public health, but cannot be enforced by law. The Agency for Toxic Substances and Disease Registry (ATSDR) and the National Institute for Occupational Safety and Health (NIOSH) are two federal organizations that develop health and safety recommendations for toxic substances.

Regulations and recommendations can be expressed as “not-to-exceed” levels, that is, levels of a toxic substance in air, water, soil, or food that do not exceed a critical value that is usually based on levels that affect animals and may become regulations as they are then adjusted to levels that will help protect humans. Sometimes these not-to-exceed levels differ among federal organizations because they used different exposure times (an 8-hour workday, 10-hour workday, 12-hour workday or a 24-hour day), along with different animal studies, or other factors.

EPA has set 5 ppb as the maximum permissible level of benzene in drinking water. EPA has set a goal of 0 ppb for benzene in drinking water and in water such as rivers and lakes because benzene can cause leukemia. EPA estimates that 10 ppb benzene in drinking water that is consumed regularly or exposure to 0.4 ppb in air over a lifetime could cause a risk of one additional cancer case for every 100,000 exposed persons. EPA recommends 200 ppb as the maximum permissible level of benzene in water for short-term exposures (10 days) for children.

EPA Position on Benzene near Refineries’ Fenceline

Interesting that EPA in December of 2015 established an action limit for refinery fence-lines at 9 ug/m3. The lowest benzene occupational limit published is 0.1 ppm. The EPA fenceline actionable benzene limit of 9 ug/m3 value is equal to .0028 ppm which is 35.7+ times lower at the fence line than for ACGIH and OSHA TWA personal monitoring limits. As I worked through all of the regulatory limits, I converted back and forth the limits to ensure that I had every limit on the chart converted properly to ppm. So the 9 ug/m3 limit that has been established by EPA is really 0.009 mg/m3.

Toxicological Data to Think About Surrounding Benzene

Here are few critical highlights as you think about benzene, benzene aromatics and these regulatory limits:

1. DNA adduct is a piece of DNA covalently bonded to a (cancer-causing) chemical. This process could be the start of a cancerous cell, or carcinogenesis (“ASTDR Benzene Toxicological Report”, n.d.).
2. Covalent adducts between chemical mutagens and DNA. Such couplings activate DNA repair processes and, unless repaired prior to DNA replication, may lead to nucleotide substitutions, deletions, and chromosome rearrangements. This is the beginning of cancer growth. What is known is that the 32P-postlabeling assay procedure for detection and quantitation of aromatic carcinogen-DNA lesions validates mutagenic changes (“ASTDR Benzene Toxicological Report”, n.d.).
3. Benzene and PAH DNA adducts cross from the placenta to the blood cord of unborn children (“ASTDR Benzene Toxicological Report”, n.d.).
4. It is not just that EPA considers benzene to be the Biomarker, the real issue is Particulate PM2.5 and the PAH/Benzene adhering to the PM (ASTDR, 2015).
5. Billings, Montana, where three refineries are located documented in 2015 that 295 days had levels of recordable 2.5 um particulates.
6. The OSHA Weight of Evidence Book published specifically to address benzene plus all the others chemicals from the OSHA Tables in Appendix C and D.
7. From a respirator perspective for protection, you are looking at wearing a full face respirator at the fenceline if you are being exposed to the numbers of published occupational exposure limits (OEL’s).
8. Benzene may potentiate the adverse effects of others by enhancing their bioactivation (Kacew & Lee, 2013).
9. Benzene is an outstanding example of a solvent affecting the hemtopoietic system where it depresses bone marrow in animals by decreasing the circulating leukocytes, thrombocytes, and erythrocytes (Kacew & Lee, 2013).
10. DNA adduct is a piece of DNA covalently bonded to a (cancer-causing) chemical. This process could be the start of a cancerous cell, or carcinogenesis (Kacew & Lee, 2013).

EPA Technology Transfer Showing Benzene Health Numbers to Regulatory Advisory Numbers

The following chart is the mother-lode of data for addressing the toxicological limits to the occupational limits. As a chemist, industrial hygienists, the key bar of the chart is the BMCL (statistical lower confidence limit on the concentration at the benchmark concentration, which is the concentration producing a specified change in a response rate that is considered a critical effect) was used as the point of departure for the Reference Concentrations (RfC) derivation (“Toxicokinetics Identified”, n.d.). The Bioorganic and Medical Chemistry Letters (BMCL) Journal describes how benzene is for hematological effects (reduction in absolute lymphocyte count) in humans. All of this data is calculated and derived from U.S. Environmental Protection Agency (“US EPA IRIS”, n.d.).

Since this limit is only current as of 2009, I have been reaching out to numerous toxicologists at National Toxicology Program (NTP) to determine if any draft studies are emerging that would change this limit. Because this was so critical for me to understand, I specifically reached out to Dr. Paul Foster, Director, telephone number, (919) 541-2513 in the NTP facility located in Research Triangle to determine if further toxicological studies or RfC derivations have been created with the new human genome studies.

Today, it is EPA’s mission to protect human health and the environment. EPA’s Integrated Risk Information System (IRIS) Program supports this mission by identifying and characterizing the health hazards of chemicals found in the environment. Each IRIS assessment can cover a chemical, a group of related chemicals, or a complex mixture (“US EPA IRS”, n.d.).

All of the value on the right side of the chart under: “Regulatory Advisory Numbers” are the Occupational Safety and Health Administration’s short-term exposure limit (OSHA/STEL), National Institute of Occupational Safety and Health’s recommended exposure limit (NIOSH/REL), NIOSH’s short term exposure limit (NIOSH/STEL), Occupational Safety and Health Administration’s permissible exposure limit expressed as a time-weighted average(OSHA/PEL/TWA), OSHA’s short term exposure limit (OSHA/STEL), American Conference of Governmental and Industrial Hygienists’ short-term exposure limit (ACGIH/STEL), American Conference of Governmental and Industrial Hygienists’ threshold limit value expressed as a time-weighted average (ACGIH/TLV/TWA), American Industrial Hygiene Association’s Emergency Response Planning Guidelines (AIHA/ERPG 1) is for 1 hour, and (AIHA/ERPG 2) is for 2 hours), which is a calculated concentration of a chemical in air to which exposure for a specific length of time is expected to cause death in 50% of a defined (LC50 (Lethal Concentration50).

Key note about regulatory limits from OSHA is that in 2013, OSHA recognized that many of its permissible exposure limits (PELs) were outdated and inadequate for ensuring protection of worker health. Most of OSHA’s PELs were issued shortly after adoption of the Occupational Safety and Health (OSH) Act in 1970, and have not been updated since that time. Section 6(a) of the OSH Act granted the agency the authority to adopt existing Federal standards or national consensus standards as enforceable OSHA standards. To provide employers, workers, and other interested parties with a list of alternate occupational exposure limits that may serve to better protect workers, OSHA has annotated the existing Z-Tables with other selected occupational exposure limits. OSHA has chosen to present a side-by-side table with the Cal/OSHA PELs, the NIOSH Recommended Exposure Limits (RELs) and the ACGIH® TLVs. The tables list air concentration limits, but do not include notations for skin absorption or sensitization (“OSHA Annotated Tables”, n.d.).

Conclusion

In industry, OSHA regulates exposure levels of benzene in the workplace. The maximum allowable amount of benzene in workroom air during an 8-hour workday, 40-hour workweek is 1 ppm. Because benzene can cause cancer, NIOSH recommends that all workers wear special breathing equipment when they are likely to be exposed to benzene at levels exceeding the recommended (8-hour) exposure limit of 0.1 ppm (“ASTDR Benzene Toxicological Report”, n.d.).

Benzene works by causing cells not to work correctly. For example, it can cause bone marrow not to produce enough red blood cells, which can lead to anemia. Also, it can damage the immune system by changing blood levels of antibodies and causing the loss of white blood cells (“CDC and Benzene Toxicological Data”, n.d.). Benzene’s genetic and mutagenic changes in humans can forever alter the landscape of families lives throughout the world.

References

ASTDR Benzene Toxicological Report examples explained. (n.d.) Retrieved from http://www.atsdr.cdc.gov/PHS/PHS.asp?id=37&tid=14#bookmark08.

ATSDR Toxicology on Benzene examples explained. (n.d.) Retrieved from http://www.atsdr.cdc.gov/toxprofiles/TP.asp?id=40&tid=14.

CDC and Benzene Toxicological Data examples explained. (n.d.) Retrieved from http://www.bt.cdc.gov/agent/benzene/basics/facts.asp.

EPA and Benzene examples explained. (n.d.) Retrieved from http://www3.epa.gov/airtoxics/hlthef/benzene.html.

OSHA Annotated Tables examples explained. (n.d.) Retrieved from https://www.osha.gov/dsg/annotated-pels/ and https://www.osha.gov/dsg/annotated-pels/tablez-1.html.

Sittig, M., (1985). Handbook of Toxic and Hazardous Chemicals and Carcinogens. 2nd ed. Noyes Publications, Park Ridge, NJ.

Toxicokinetics Identified examples explained. (n.d.) Retrieved from http://www.crios.be/Benzene/toxicology.htm.

U.S. Environmental Protection Agency IRIS examples explained. (n.d.) Retrieved from http://www.epa.gov/iris.