emerging contaminants

April 3, 2024

Join SCS Engineers at the 34th Annual Environment Virginia Symposium at the Virginia Military Institute in Lexington, Virginia. The event is cohosted by state agencies and organizations, including the Virginia Department of Environmental Quality (VADEQ) and Virginia Environmental Endowment. As the Commonwealth’s premier environmental conference, it brings together environmental professionals from all sectors: government, non-profits, academia, and industry throughout Virginia. The agenda includes about thirty sessions with topics ranging from climate resilience to emerging contaminants, notable speakers, workshops, and opportunities for professionals to earn CEUs. Featured events include a keynote address by Governor Glenn Youngkin, a “Rising Leaders” workshop, and a poster showcase for college students to share their research.

Register today for this exciting event!

Posted by Brianna Morgan at 1:04 pm

October 11, 2023

Emerging contaminants - 6PPD - 6PPD-quinone - 6PPD-q
Recent studies have shown that the reaction of 6PPD in rubber tires with the oxygen and ozone in the air generates transformation products, including 6PPD-quinone. Many questions remain unanswered before we better understand the environmental and toxicological impacts of 6PPD-q and develop potential solutions; here are some ongoing efforts.


In response to a significant decrease in salmonid fish populations in urban streams, including several listed under the Endangered Species Act (ESA), several West Coast organizations conducted studies to evaluate the cause. In 2020, a culprit was identified – a breakdown compound commonly found in tires: 6PPD.

6PPD (N-(1,3-Dimethylbutyl)-N’-phenyl-p-phenylenediamine; C18H24N2 CAS 793-24-8) is an additive in the manufacturing of both natural rubber and common synthetic rubbers such as butyl rubber and styrene-butadiene rubber. It is a highly effective anti-oxidant. In layman’s terms, it helps tires resist degradation caused by exposure to oxygen, ozone, and fluctuating temperatures. According to the US Tire Manufacturers Association (USTMA), all USTMA members use it (USTMA website, 15 Aug 2023).

Recent studies have shown that the reaction of 6PPD in rubber tires with the oxygen and ozone in the air generates transformation products, including storm (6PPD-q; 2-((4-Methylpentan-2-yl) amino)-5-(phenylamino) cyclohexa-2,5-diene-1,4-dione; C18H22N2O2; CAS 2754428-18-5).

6ppd rubber


As tires wear, tire wear particles (TWP) and fragments containing 6PPD-q can be carried by stormwater runoff from roadways and parking lots to aquatic environments, such as salmonid spawning streams.

For instance, recent studies indicate that 6PPD-q present in such waters may be acutely toxic to coho salmon, including juveniles. A study by Tian and others indicates that 6PPD-q toxicity to coho salmon ranks among the most toxic chemicals for which the US Environmental Protection Agency has established aquatic life criteria.

Subsequent studies indicate that 6PPD-q exhibits large differences in species sensitivity, with reduced toxicity to steelhead trout, Chinook salmon, rainbow trout, and brook trout. No mortality was observed with sockeye salmon, chum salmon, Atlantic salmon, brown trout arctic char, and white sturgeon. Regardless, the impacts on coho salmon and other species may be significant.

Many questions remain unanswered before we better understand the environmental and toxicological impacts of 6PPD-q and develop potential solutions. Ongoing efforts include the following:

  • USTMA is working with the World Business Council for Sustainable Development, Tire Industry Panel (TIP), and others to lead research efforts to fill data gaps. USTMA also works with EPA and state regulatory agencies in California, Alaska, Oregon, and Washington State.
  • The Interstate Technology Regulatory Council (ITRC) developed a new Tire Anti-Degradants Team in 2023.
  • US EPA is considering 6PPD-q for the sixth Candidate Contaminant List (CCL). The CCL is a list of contaminants currently not subject to any proposed or promulgated national primary drinking water regulations that are known or anticipated to occur in public water systems and may require regulation under the Safe Drinking Water Act (SDWA).
  • The Puget Sound Federal Task Force Action Plan, 2022-2026, includes a series of goals related to 6PPD and 6PPD-q, including the development and standardization of analytical methods and additional aquatic toxicity research.

Whether 6PPD-q contamination will become a significant issue outside spawning regions of coho salmon and other ESA-listed fish species remains to be seen. Bioaccumulation in higher-order animals may also be an issue; more research is underway.


About the Authors:

Jeff MarshallJeff Marshall, PE in five states, is a vice president and the practice leader for the Environmental Services Practice for SCS offices on the eastern seaboard. He also serves as the SCS National Partner for Innovative Technologies and Emerging Contaminants. He has a diversified background in project engineering and management, with emphasis on the environmental chemistry and human health aspects of hazardous materials/waste management, site investigations, waste treatment, risk-based remediation and redevelopment, and environmental compliance/permitting issues.

shane latimerDr. Shane Latimer, CSE, is an SCS vice president. He is an environmental planner, ecologist, and toxicologist with three decades of experience in environmental assessment, planning, permitting, and implementation. His specialty is developing projects that challenge the interface between the built and natural environment, such as solid waste facilities, oil and gas infrastructure, mines, sewage treatment facilities, and similar developments. Solutions for these projects often require careful assessments of alternatives, impacts, and opportunities to successfully navigate the applicable public regulatory processes (e.g., NEPA, local land use, etc.) and ensure environmental integrity.




Posted by Diane Samuels at 6:00 am

August 27, 2020

scs engineers remediation - soil, air, water - emerging contaminants such as PFAS

Perfluoroalkyl and polyfluroalkyl substances (PFAS) and other emerging contaminants are becoming increasingly important for real estate transactions.  Several states have adopted or proposed health guidelines or Maximum Contaminant Levels (MCLs) for PFAS in their state. States with adopted limits include CA, CT, CO, MN, NC, NH, NJ, and VT; and states with proposed limits include IL, MA, MI, and NY.  You can track bills by state here.

The Wisconsin Department of Natural Resources (WDNR) and the Environmental Protection Agency (EPA) are focusing their attention on these contaminants. The WDNR recently issued letters to more than 3,000 responsible parties listed with open cases on the DNR’s Bureau for Remediation and Redevelopment Tracking System (BRRTS) requesting they review PFAS use at open sites. Read a sample of the DNR letter.

With WDNR’s increasing focus on PFAS, a lack of sufficient due diligence, which includes evaluations for PFAS, could lead to significant additional liability for property purchasers, developers, and lenders. In addition, a lack of sufficient assessment could lead to a delay in case closure even after responsible parties have addressed all other contaminants and potential exposure pathways at a site. A sufficient assessment for PFAS will depend on site-specific factors and should carefully consider the associated risks and liabilities.

For real estate buyers, owners, developers, lenders, brokers, and contractors the potential presence of PFAS at a property presents significant liabilities that need to be incorporated into due diligence procedures and safe work plans. The investigation and remediation of sites with PFAS contamination can be expensive, and the WDNR is working to define enforceable cleanup goals for soil and groundwater.


  1. Get clarification of your responsibilities state-by-state.
  2. Environmental Due Diligence and All Appropriate Inquiries
  3. Remediation and Brownfields


About PFAS

PFAS are often referred to as “forever chemicals” due to their inability to be broken down in the environment. Due to the very high toxicity of PFAS, the proposed groundwater standard is extremely low – in the parts per trillion, which is more than 100 times lower than the groundwater standards for other well-known toxic contaminants such as benzene from gasoline or tetrachloroethylene commonly used at dry cleaners and industrial facilities.

PFAS are found in a wide variety of products, including nonstick coatings (e.g., Teflon), water-repellent coatings used on clothing and food packaging, fume suppressants, and firefighting foams. Potential sources of PFAS include many types of manufacturing and processing facilities, locations where firefighting foams have been used, metal plating facilities, wastewater treatment plants, and many more.

PFAS systems can treat and clean sources and remediation solutions by environmental engineers can bring properties back to life; safe to build and live on.





Posted by Diane Samuels at 6:00 am

January 22, 2020


When a release of PFAS occurs at a metal finishing facility, it is often due to the integrity of the wastewater system. Due to the persistence of PFAS and very low concentrations considered to be toxic, even water containing a small amount of PFAS can result in a large impact on the environment. If water can migrate into the subsurface, so can PFAS. Once in the soil, any water introduced into the soil can transport the PFAS into the groundwater.

The Californian chrome plating facilities are being required to test for PFAS even if there is no evidence of historical contamination at the property from any chemicals. Current testing is requiring the analysis of 25 different kinds of PFAS, including PFOS and 6:2 FTS.

Because such low concentrations of PFAS are considered to be toxic and their prevalence in common consumer products and tools, false-positive detections are common during the investigations for PFAS. False positives detections can lead to unnecessary expense and additional investigations. Therefore, selecting a knowledgeable, skilled, and experienced environmental consulting firm, is paramount to keeping the investigation as low cost as possible.

The author is Lynleigh Love a Senior Professional Geologist at SCS Engineers specializing in emerging contaminants.

To purchase, read, or cite this article: https://doi.org/10.1080/00202967.2020.1696597

(2020) Upcoming mandatory testing requirements for chromium plating facilities, Transactions of the IMF, 98:1, 6-7, DOI: 10.1080/00202967.2020.1696597.


Learn more about PFAS and the impact on industrial wastewater pretreatment and groundwater protection.







Posted by Diane Samuels at 6:01 am

January 14, 2020

The U.S. Environmental Protection Agency (EPA) has identified 1, 2, 3 – Trichloropropane (TCP), which does not occur naturally in the environment, as an emerging chemical of concern that can threaten drinking water supplies. It states that TCP is a persistent pollutant in groundwater and has classified it as “likely to be carcinogenic to humans.” California State Water Board member Steven Moore called TCP an “insidious chemical” because it persists in the environment, sinks in water and is harmful in even tiny doses. Currently, there is no federal maximum contamination level (MCL) for TCP; however, there is a federal non-enforceable health-based screening level of 0.00075 ug/L.

Since 2012, TCP has been on the emerging Contaminant Candidate List (CCL), which is a watch list of unregulated contaminants that are known to, or anticipated to, occur in public water systems and may require regulation under the Safe Drinking Water Act (SDWA). The EPA has required, under the Unregulated Contaminant Monitoring Rule (UCMR), that large water systems test for TCP every five years with a minimum reporting level of 0.03 μg/L. This rule allows for the EPA to monitor contaminants suspected to be in drinking water that are unregulated under the SDWA. As a result of the testing, TCP has been identified across the US in drinking water sources. Currently, there is no federal maximum contamination level (MCL) for TCP; there is a federal non-enforceable health-based screening level of 0.00075 ug/L.

The author continues the paper with an examination of what TCP is and how it impacts our environment and our health. She then discusses regulatory policies and how California’s mandatory TCP standard could be a blueprint for other state water agencies currently investigating how to enhance their own drinking water protections from emerging contaminants.

Lyn covers some of the legal aspects, risks to businesses, detection, and treatment options to conclude her white paper. She also provides plenty of resources to start the journey toward sustainable treatment solutions that communities can afford.


Continue reading, share, or download the informative paper “1, 2, 3 – TCP: California’s Response to a Persistent Pollutant,”  by Lynleigh Love, SCS Engineers. 


Lynleigh LoveAbout the Author: Lynleigh Love is a Senior Project Geologist with SCS Engineers. She has been a professional geologist for more than 22 years with extensive technical expertise in environmental assessment, remediation, and regulatory compliance. Her experience includes groundwater/soil vapor monitoring, excavation work plans, and remedial action plans.







Posted by Diane Samuels at 6:03 am

January 9, 2020

PFAS are also key components in aqueous film-forming foam (AFFF), which is used to fight petroleum-based fires at aviation and manufacturing facilities. For decades, AFFF containing PFAS has been used extensively at airports throughout the world to protect the safety of passengers, crew, and others. The FAA requires that commercial airports train with, calibrate equipment with, and use the best performing AFFF fire suppression systems. AFFF is required to be used at airports and must be certified to meet strict performance specifications, including those mandated by the  U.S. Department of Defense Military Specifications.

How can airports, the aviation industry, and manufacturers begin to mitigate PFAS health risks?


Lynleigh Love and Chris Crosby of SCS Engineers discuss the risks and issues with PFAS-based firefighting foam used at airports. The authors cover the regulatory climate,  contamination investigations,  operational and environmental management and litigation, along with alternatives to using traditional AFFF. There are some possible alternatives that can mitigate health risks in your community.

Read this article to help inform your mitigation plan and strategies to minimize risk.






Posted by Diane Samuels at 2:35 pm

July 29, 2019

Forester University recently hosted Dr. Viraj deSilva P.E., BCEE of SCS Engineers in their well-received educational webinar “All About PFAS: Emerging Contaminants That Are Everywhere.”

Dr. deSilva teaches you all you need to know to protect yourself and your community from PFAS—from generation, formation, and environmental release to sampling and analysis.

He provides an in-depth overview of the treatment of PFAS in sources that do not currently have maximum containment levels, such as landfill leachate, wastewater, surface water, and groundwater.

This course covers nomenclature, chemistry, sources, exposure, and future concerns as well as discusses the current regulatory status of these contaminants.

Learning Objectives

  • Identify sources of PFAS contamination and associated health concerns
  • Learning the chemical properties of PFAS compounds and why they are hard to degrade
  • Taking an inventory of detected PFAS compounds in landfill leachate, wastewater, and drinking water
  • Discovering methods used to analyze PFAS samples
  • Discussing the current regulatory status of PFAS chemicals
  • Exploring the treatment methods of PFAS compounds and managing waste streams from these treatment processes
  • Comparing PFAS concentrated residual management options and associated issues


We encourage our readers to see the webinar on Forester University’s website. Credits: 1 PDH / 0.1 CEU. Forester offers registration savings to groups. Register here.

Additional Resources with Links – click to read






Posted by Diane Samuels at 6:03 am