Dr. Rachel Y. Chang passed the American Board of Toxicology examination to become a Diplomate of American Board of Toxicology (DABT).

Ifeoluwa A. Bamgbose, M.S. passed the American Board of Toxicology examination to become a Diplomate of American Board of Toxicology (DABT).

Update on OELs in Development

Occupational exposure limits (OELs) are airborne concentrations of chemicals recommended as guidance or promulgated as regulatory exposure limits for the protection of worker health. Periodically, OEL-setting organizations develop new limits for chemicals that lack them and re-evaluate existing limits, which they either retain or revise. Below, we provide updates on the current work of the major OEL-setting organizations in the US.

American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLVs)
ACGIH’s TLV-Chemical Substance (TLV-CS) Committee identifies chemicals and physical agents for which to develop or revise TLVs and places them on its “Under Study” list.  Every year, the Committee issues proposed new or revised TLVs in the form of Notices of Intended Changes (NICs).

The Notices of Intended Changes Issued by ACGIH

OEL Alert Chart 1

Notes:  STEL = Short-Term Exposure Limit. (a) Values are time-weighted averages (TWAs), unless otherwise noted.

In September 2022, ACGIH announced several changes to its TLV development process for 2023: the “Under Study” list will no longer be tiered, the Committee will be able to add chemicals to the list at any time, and comment periods for NICs will be offered twice per year, each lasting three months.

Occupational Safety and Health Administration (OSHA) Permissible Exposure Limits (PELs)
OSHA has not indicated that any PELs are currently in development.

National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limits (RELs)
Currently, NIOSH notes that RELs for two chemicals are “under development” – toluene diisocyanate and 1-bromopropane. However, NIOSH last updated the “Peer Review Agenda” information for these RELs in 2016.

Occupational Alliance for Risk Science (OARS) Workplace Environmental Exposure Levels (WEELs)
This year, the OARS WEEL Committee developed a new WEEL for difluoroethylene, (E)-1,2 (HFO-1132 [E]) (350 ppm). WEELs for dimethyl ether and triethylenetetramine (TETA) are currently in the public comment stage.

As part of OEL development, many OEL-setting organizations offer opportunities for organizations to provide comments and/or submit data or other information about chemicals as part of their OEL development processes. Gradient scientists understand occupational exposures and the studies upon which OELs are based; we can support clients who want to contribute to the OEL-setting process for chemicals of importance to them. We provide information, analysis, and advice on a wide range of occupational health and risk issues.


Lisa A. Bailey, Ph.D.
Principal Scientist

David G. Dodge, M.S., DABT, CIH
Principal Scientist

Julie C. Lemay, M.P.H.
Senior Environmental Health Scientist

Tom A. Lewandowski, Ph.D., DABT, ERT, ATS

Christopher M. Long, Sc.D., DABT

Gradient is pleased to announce that Chris DesAutels has joined the firm as a Principal Scientist. Chris is an air modeler with over 20 years of experience simulating the transport of air pollutants, conducting air quality modeling studies, and performing analyses of meteorological data. His experience covers a variety of applications and industry sectors, including transportation, agriculture, fugitive dust, odors, and dense gas releases. He has also been involved in air model software development and evaluation, including development work on the CALPUFF dispersion model.

In addition, Gradient welcomes Dr. Amy Hrdina who joins Gradient after completing a postdoc at Massachusetts Institute of Technology. Dr. Hrdina is an atmospheric chemist with a broad background in materials and analytical chemistry. She has conducted several field campaigns monitoring criteria pollutants, along with studying atmospheric ammonia and its role in secondary particle formation.

These additions to our team complement Gradient’s robust capabilities in exposure modeling and risk assessment. See more on Gradient’s Air Quality services.


California’s New Safe Harbor Regulations Warn That Cannabis During Pregnancy Can Affect Child Birthweight, Behavior, and Learning Ability

As of October 1, 2022, California has adopted new safe harbor warnings for cannabis under Proposition 65. These warnings provide language on the potential adverse effects of prenatal cannabis exposure and may have implications for certain cannabis product manufacturers and businesses.

The California Office of Environmental Health Hazard Assessment (OEHHA) has issued new regulations regarding specific safe harbor exposure warnings, particularly during pregnancy. The regulations state that certain cannabis products and businesses need to include new safe harbor warning language in their labeling and/or signage in order to maintain compliance under California Proposition 65.

OEHHA’s new safe harbor warnings apply to cannabis products with the potential for exposure to cannabis smoke or delta-9-tetrahydrocannabinol (delta-9-THC) via inhalation, ingestion, or dermal application. Further, the new warnings apply to potential environmental exposures to cannabis smoke or delta-9-THC from businesses where delta-9-THC is smoked, vaped, or dabbed (i.e., inhaled in small quantities).

The new safe harbor warnings for cannabis are unique, as they include specific language regarding potential adverse effects from cannabis exposure during pregnancy. For example, to maintain compliance, cannabis products intended to be smoked need to warn consumers that the State has determined that smoking cannabis increases cancer risk and during pregnancy exposes a child to delta-9-THC and other chemicals that can affect the child’s birthweight, behavior, and learning ability. This updated language may reflect a change in OEHHA’s approach for labeling certain products under Proposition 65, where greater detail may be required in warnings. Further, OEHHA determined that use of the popular short-form warning for cannabis products is insufficient because it “does not provide the level of specificity needed for cannabis (marijuana) smoke and delta-9-THC exposures.” OEHHA continues, stating that the new safe harbor warning language “clearly conveys the adverse developmental effects cannabis smoke and delta-9-THC can cause when used by pregnant women.”

OEHHA allows for a one-year transition period for businesses to label their products with compliant warnings. OEHHA also states that businesses are free to substitute their own warning language for the agency’s wording; however, the use of OEHHA’s language is a defense against claims that other warning language does not meet the “clear and reasonable standard.” This suggests that certain businesses may risk non-compliance if they choose to develop their own safe harbor warning.

For more information, refer to OEHHA’s website and/or contact Gradient.

Topics:  Cannabis, Delta-9-THC, Pregnancy, Proposition 65, Product and Consumer Safety


Steven Boomhower, Ph.D.
Senior Toxicologist

Tom Lewandowski, Ph.D., DABT, ERT, ATS

Kim Reynolds Reid
Principal Scientist

James Rice, Ph.D.
Senior Environmental Scientist


Increased Funding Supports Fenceline Monitoring Near Environmental Justice Communities

Topics:  Environmental Justice, Fenceline Air Monitoring, Air Quality and Emissions, Industrial Emissions Impacts

Recent funding for community and fenceline air monitoring presents significant opportunity to better understand and mitigate industrial emissions impacts on neighboring communities, especially within environmental justice communities.

With the passage of the Inflation Reduction Act of 2022, community and fenceline air monitoring will see a significant increase in funding, especially within environmental justice communities. United States Environmental Protection Agency (US EPA) will be provided with $117.5 million for fenceline and community monitoring efforts through 2031, with another $3 million to be allocated to installing air quality sensors in low income and disadvantaged communities. In addition, Environmental and Climate Justice Block Grants will provide $3 billion in potential funding for fenceline and community monitoring projects put forward by local governments and community-based non-profits through 2026.

This funding builds on US EPA’s growing focus on using fenceline and community monitoring to better understand and mitigate industrial emissions impacts on neighboring communities. Initial passage of US EPA’s Refinery Rule in 2015 instituted benzene fenceline monitoring requirements for petroleum refineries. Subsequent state actions (California AB1647, Colorado HB21-1189) and US EPA settlement agreements have gradually expanded this practice to other pollutants and industries. The new funding of the Inflation Reduction Act can be expected to greatly expand the collection and availability of monitoring data, with an increase in the number of monitoring networks designed and run by government and nonprofit groups.

Understanding the relative contribution of different sources of air emissions and assessing cumulative impacts from chemical and nonchemical stressors will be important.

Expanded fenceline monitoring represents a significant opportunity to better understand and control emissions. Fugitive sources, leaks, and accidental releases can be better quantified and mitigated, allowing facilities the opportunity to rectify short-term problems before they represent long-term risks to the community. However, the public availability of this data comes with challenges in effective risk evaluation, community engagement, and risk communication, particularly in the context of understanding the relative contribution of different sources of air emissions and assessing cumulative impacts from chemical and nonchemical stressors.

Gradient is positioned to assist clients at this intersection of industrial activity, government policy, and community engagement. Our scientists are at the forefront of air quality, air emissions, and risk assessment, and excel at interpreting and communicating the meaning of complex data to community and government agencies. If you have questions about how expanded fenceline monitoring may impact your industry, please contact Gradient.


Christopher DesAutels, M.S.
Principal Scientist

Ari S. Lewis, M.S.

Julie C. Lemay, M.P.H.
Senior Environmental Health Scientist

Chris M. Long, Sc. D., DABT


Inflation Reduction Act of 2022

US EPA’s Refinery Rule

California AB1647

Colorado HB21-1189

Gradient will have six presentations at the MGP Conference 2022, taking place September 28-30 in Chicago, Illinois. Click the links below to view the presentation and poster abstracts.

Gradient’s 2022 MGP Presentations and Posters:

“Soil Vapor Fingerprinting to Differentiate Petrogenic and Pyrogenic Sources”
James Rice
Session 1: Innovative Site Characterization Techniques
09/28/22 @ 1:25 pm-1:45 pm


“Weight-of-Evidence Approach to Estimate Release Timing at a Former MGP Site”
John Kondziolka
Session 1: Innovative Site Characterization Techniques
09/28/22 @ 2:25 pm-2:45 pm

“Environmental Justice and the MGP Community Programs and Screening Tools”
Matthew Mayo
Session 7: Community Relations
09/29/22 @ 4:15 pm-4:35 pm

“Risk-based Remediation Case Study”

Meghna Swamy
Session 8: Remediation Case Studies
09/30/22 @ 8:45 am-9:05 am


“Historical Assessments of Former Manufactured Gas Plant Sites”
Anna Engel



“Key Findings Regarding Soil Gas Sampling at Former Manufactured Gas Distribution Holder Sites”
Kurt Herman


Gradient will have four presentations at the SETAC North America 43rd Annual Meeting, taking place November 13-17, 2022, in Pittsburgh, PA. Click the links below to view the presentation and poster abstracts.

Gradient’s 2022 SETAC Presentations and Posters:

“4.15.T-03 – Evaluating Exposure and Risk in Fenceline Communities: The Uses and Limitations of Publicly Available Geographic Information System (GIS)-Based Tools”
Ari Lewis, Julie Lemay, Naomi Slagowski
Session 4.15: Life at the Fenceline – State-of-the-Science Exposure Assessment for Communities Adjacent to Industrial Facilities
11/14/22 @ 2:40 pm-2:55 pm

“5.11.T-07 – When Molecules Fall Apart: New Approach Methodologies for Chemicals That Dissociate”
Jessie Kneeland, Chase Butler, Anya Chinniah, Patricia Clyde
Session 5.11: In Silico NAMs: Recent Developments and Regulatory Applications
11/16/22 @ 12:00 pm-12:15 pm

“4.20.P-We156 – Read-Across: A Promising Tool for Predicting Removal of Chemicals of Emerging Concern from Wastewater”
Patricia Clyde, Anya Chinniah, Jessie Kneeland
Session 4.20: Chemistry and Exposure (Poster Only)
11/16/22 @ 8:00 am-6:00 pm

“8.01.T-06 – A Trade Name Market Differentiator: Case Studies Under the ChemFORWARD SAFER Program”
Jiaru Zhang, Charlotte Marsh, Kim Reynolds Reid, Patrick Harmon
Session 8.01: Advances in Methods, Policies, and Practices for Safer and More Sustainable Alternatives
11/17/22 @ 11:40 am-11:55 am



Gradient will be presenting three posters at the American College of Toxicology 43rd Annual Meeting, taking place November 13-16, 2022, in Denver, CO. Click the links below to view the poster abstracts.

Gradient’s 2022 ACT Posters:

“Environmental Assessment for Human Drug Approval – An Outdated Technical Framework?”
Ifeoluwa Bamgbose, Tim Verslycke

“Safety Review of Residual CRISPR-Cas Components in Biologics – A Toxicological Perspective”
Isaac Mohar, Archit Rastogi

“A Dermal Sensitization Threshold (DST) for Device Extractables”
Rebecca Ticknor, Isaac Mohar, Joel Cohen, and Tom Lewandowski

Updates on Asbestos Regulation Under TSCA

The Toxic Substances Control Act (TSCA), as amended by the Frank R. Lautenberg Chemical Safety for the 21st Century Act, requires the United States Environmental Protection Agency (US EPA) to evaluate the safety of existing chemicals in three stages: prioritization, risk evaluation, and risk management.

In 2016, asbestos was prioritized as one of the first ten chemicals to undergo risk evaluation in this process. US EPA initially focused on chrysotile asbestos, as it is the only asbestos fiber type currently imported, processed, or distributed in the US. The agency completed the final risk evaluation for chrysotile asbestos (Part 1) in December, 2020. In this evaluation, the agency concluded that some consumer and commercial uses of chrysotile asbestos-containing automotive brakes and clutches, as well as the industrial use of chrysotile asbestos-containing diaphragms in the chlor-alkali industry, sheet gaskets in chemical production, and brake blocks in the oil industry, result in unreasonable cancer risks. In December, 2021, US EPA released the draft scope for Part 2 of the risk evaluation of asbestos, which is a supplemental effort to evaluate legacy uses and associated disposals of asbestos, other types of asbestos fibers in addition to chrysotile, and conditions of use of asbestos in talc and talc-containing products.

Currently, US EPA is moving forward with risk management actions related to Part 1 of the chrysotile asbestos evaluation. In April, 2022, US EPA proposed a ban of ongoing uses of chrysotile asbestos, based on its findings of unreasonable risks to human health in the Part 1 evaluation. This proposed ban would prohibit the manufacture, import, processing, distribution in commerce, and commercial use of chrysotile asbestos for:

Gradient submitted comments to US EPA on a draft of the Part 1 chrysotile risk evaluation and also provided comments on the Part 2 draft scope (as included in the Industrial Minerals Association – North America submission to US EPA). US EPA is accepting public comments on the proposed rule to ban ongoing uses of chrysotile asbestos until July 13, 2022. US EPA is also accepting public comments until July 5, 2022, on a proposed rule that would require those who manufactured or processed asbestos and asbestos-containing articles (including as an impurity) in the last four years to report certain exposure-related information, such as quantities of asbestos manufactured or processed and the types of use. There will be additional opportunities for public comment as US EPA continues the evaluation process for asbestos, including a public comment period on a draft of the Part 2 risk evaluation. US EPA is required by court order to publish Part 2 of the final risk evaluation for asbestos by December 1, 2024.

Gradient has been tracking the evolving science, state of knowledge, and regulatory decisions regarding asbestos for decades. If you have questions related to asbestos, please visit our website or contact:

Lisa Bailey, Ph.D.
Principal Scientist

David Dodge, M.S., DABT, CIH
Principal Scientist

Julie Goodman, Ph.D., DABT, FACE, ATS

Michael K. Peterson, M.E.M., DABT

Robyn Prueitt, Ph.D., DABT
Principal Scientist

Topics:  Asbestos, Chrysotile Asbestos, TSCA, Chemical Safety Review