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Whatever happened to the copper in brake pads? Part 1 of 2

It was mid 1995. I was looking through my office window over the blue grass hills in Winchester, Kentucky, feet on the table, pen and paper on the table staring at me. My train of thought was disrupted by the receptionist’s voice: Greg from Stanford Law School is on the phone for you! Um, Stanford Law School was the first thing came to my mind!? I have always been interested in getting a Law degree, but never applied to any school. Could it be that they are going to offer me admission without me even applying!? I answered the phone.

Greg referred to me as a friction material industry expert. He had combed the industry and invited me, Dr. Tim Merkel of Abex, Dr. Marvin Weintraub of Ford Motor Company, and the late Dr. Jim Trainer, a consultant in brake friction material. Greg explained briefly that I and the others were invited to attend a meeting to discuss the effect of copper from brake pad emissions on the South San Francisco Bay. So, let’s see first what the function of copper in friction brakes is:

  • Copper is a lubricant

  • Copper prevents transfer layer

  • Copper is an excellent conductor of heat

  • Copper fiber offers strength

  • Copper helps stabilize the coefficient of friction

  • Copper helps improve lining durability

  • Copper helps improving Judder and DTV

  • Copper has great synergy with other ingredients in the mix

In addition to the four of us from the industry, the following organizations were also represented:

  • Brake Manufacturers Council

  • California Storm Water Quality Association

  • Sierra Club

  • Sustainable Conservation (Project Manager), and

  • Water Resources Control for San Francisco

With time, both federal and state EPA organizations were represented too.

We were gathered to be informed that the copper level in the South San Francisco Bay was of concern in the 1980s because of interference in the food chain and it was elevated now in the mid 1990s. The blame for the high concentration of copper in the Bay was squarely placed on the copper content of brake friction materials. To prove this was possible a selective number of brake pads, based on vehicle popularity in the Bay Area, were purchased by the environmental stakeholders and tested at Woodward-Clyde lab. The test results showed copper content as high as 15% in a set of purchased pads.

Of course, the brake manufacturers immediately questioned all other sources of copper, i.e., copper piping, airport runway ships and boats, etc., all of which we were told had been accounted for. We still had objections to the study, methodology, selection of brake pads for testing and more. Jim Trainer asked, “what the end game is?” and “what’s the view from 10,000 feet?” But we hardly had digested the beginning of the game, let alone the end, and we could not see the view from 10 feet let alone 10,000! The four of us, especially Tim and I who had come from the manufacturing side and stood the chance to be affected by all this, came in skeptical and left even more so. It was difficult to understand how a metal with limited solubility could be interfering in the food chain. However, we had an open mind about it and were willing to listen.

This became a hot subject of discussion amongst the members in Brake Manufacturers Council and other related industry meetings. I moved on from manufacturing to Tier I/OE and hence was not directly involved anymore. Soon a Brake Pad Partnership was formed between the manufacturers and the stakeholders collaborating to see how the clams in the Bay may start to reproduce again, as they had allegedly stopped because of copper contamination in the Bay, and how the salmon will start traveling in the right direction to reproduce. That was my take at the end of Day 1.

Or as described on Memorandum of Understanding (MOU):

"Elevated levels of copper are toxic in aquatic environments and may adversely affect fish, invertebrates, plants and amphibians. Acute toxic effects may include mortality of three organisms, and chronic toxicity can result in reductions in survival, reproduction, and growth. Copper is also directly toxic to the salmon olfactory system, even at very low exposure concentrations, and degrades salmon’s ability to avoid predators.” More on MOU on Part 2 of this series.

So, the story behind the copper in the Bay was that every time you apply the brake, debris are generated. The debris, depending on their specific gravity, would either become airborne or deposited on the road. When it rains, the debris are carried via stormwater into the San Francisco Bay, hence causing the contamination. The brake manufacturers were tasked to start thinking about removing the copper over time, eventually arriving at near zero copper content in a brake pad. Tall order, indeed!

What started as “we don’t like your results and demands” gradually turned into a Stockholm Syndrome! Because of the expert guidance of Sustainable Conservation and the Brake Pad Partnership Steering Committee Brake manufacturers not only started collaborating whole heartedly with the environmentalists, but also at times helped them financially so that they could continue collaborating. Fresh thinking came into both sides in a way of younger generations of scientist from the industry and the environmentalist. Time flew. Disagreements turned into maybe we can work it out! As time went on, we all learned to listen to others and compromise where necessary so that everyone could win. More importantly, we started to see the issues from the other side’s point of view. Now, every stakeholder’s mind set was geared toward a resolution of the crises rather than indifference. Little to know that we were in the process of making a powerful workable model to process our differences towards a common goal. California was joined by the state of Washington in their collective efforts to have the copper removed from brake pads to protect the salmon industry. Governor Davis, a Democrat, had lost his recall bet in California and none other than Arnold Schwarzenegger, a Republican replaced him. Now, what did Arnold Schwarzenegger have to do with copper free brake pads? That, I will discuss in my next blog…

In researching these articles, I would like to acknowledge the contributions from Steve Brown, Laurie Holmes of MEMA, Kelly Maron, PhD, Bob Peters, Mark Phipps, PhD, and Marvin Weintraub, PhD. Special thanks to Tim Merkle, PhD for having read and reread my part 1 & 2 blogs with patience and constructive comments.

Mohammad Vakili has been in Friction related technology for over four decades. He holds a BS and MS in Chemical Engineering from U. Mass. He is the Founder and one of the instructors in Brake Academy.


May 09, 2022

Great read! Thank you for the trip down memory lane of what we all went through in getting regulations in place to resolve this very real issue.

Steve Hughes


Apr 13, 2022

Andreas Storz 1st degree connection1stMaterials, Surfaces and more


We need to get rid of the abrasive friction in wheel brakes! Those generate significant amounts of ultra-fine to nano-scale particles, most of them conductive metallics, which lead to inflammation reactions in the human body, including the brain.

Apr 13, 2022
Replying to

Mohammad VakiliAuthorFounder, CEO Brake Academy. Consultant & Instructor of Friction Material at SAE & Globally. Expert witness in Asbestos & Brake related litigations.


Very valid point indeed Andreas. Currently, there are lots of studies surrounding the brake coupling debris. They are mostly focused on PM and PN with some minor work towards debris epidemiological affect. In Europe, for example, that is part of the Euro 7/VII Regulations to be released in July 2022. To your point, for as long as conventional brakes are part of the both EV and ICE vehicles, brake debris are generated and airborne or ground deposited. One may take a toothpick and go through friction material formulation, one-by-one, to see how we can make it…


Apr 13, 2022

Sunny Sun

Brake Bads&Brake Disc Top Manufacturer|Focus On Provide Brake Part


Hope to read more articles from you dear Mohammad to learn more about the friction material of brake pads.

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