Boats have 999 problems, but PM ‘aint one

There’s a dark side to the EV industry that we’re not talking about enough - fine particulates. This pollutant stream can lead to more health risks than tailpipe emissions. Almost every vehicle on the road contributes to this, EVs are among the worst offenders.

What is it?

Particulate Matter (PM) comes in many forms (liquid, or solid), and can refer to most any mixture of materials. We categorize them by size because that changes how they affect our lungs. PM10 (10 microns or less) is inhalable like dust, and PM2.5 is finer still and can transit deeper into our tissues (see this excellent CARB article).

Where does it come from?

Everywhere really, even from natural sources, but the transportation sector is near the top. Diesel exhaust particulates in the US are particularly toxic. So how can EVs possibly be worse than gas cars? The problem is the consumables all vehicles use - namely brake pads and tires.

Brake pads are fiber and metal compounds that get ground into tiny dust that drifts off the brakes, collecting on our wheels like a fine mist. It also collects on roadways and wafts of it are inhaled by anyone close enough to breath it in.

The same is true for tires. On the raceway it’s called traction, in the engineering lab it’s called friction. That interface between pavement and rubber is the same effect as filing your nails. Tire dust may be one of the most problematic sources of microplastic pollution we face.

All road-going vehicles contribute to PMs, even bikes, but weight matters. Big batteries mean big EVs which now translates to more friction and more particulate. EVs are able to offset some of their brake wear by using regenerative braking, but you can’t escape that on average they weigh 33% more than their gas counterparts.

How does it hurt us?

Globally the World Health Organization (WHO) estimates that 3% of cardiopulmonary and 5% of lung cancer deaths are attributed to PM. There are also demonstrated short-term effects, such as decreased cognition and links to depression. PMs are particularly tough on sensitive groups such as those with asthma. Residents closest to dense roadways will experience the worst effects, which often tend to be impoverished and lower-income families.

PMs also impact the local rivers and lakes we play in. Stormwater runoff from roads finds its way into aquifers, making them more acidic and harming wildlife. The story of how the US salmon population is being decimated by the tire chemical 6PPD-quinone is especially tragic and needs more visibility. We just don’t know the long term risks of many of these pollutants.

What can you do?

I have been caught excitedly dropping the term “6PPD-Q” at cocktail hour, but that may be a character flaw. Awareness is an issue; we need to shine a light on that soot that coats our wheels. When it’s time to swap your brakes or tires next, see if there are better alternatives - the EU Euro 7 standards are forcing the industry to start changing.

What else can you do? Go by boat of course! There are surely more than 999 things that need maintenance on your boat but (unless you own a duck boat) brakes and tires aren’t two of them. Find ways to reduce the mileage you spend in your car and reduce the weight on your tires when you can.

It’s more fun to float anyway!