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The Air/Water Connection: PM10

In California the car is king - an object of adoration, a ticket to liberty, an appendage as indispensable as a right arm - which is why no one likes to hear about how bad cars are for the planet. But we're going to hear more.

"Maybe we can give the public one more reason to stop driving so much," says Geoff Brosseau of the Bay Area Stormwater Management Agencies Association, referring to growing awareness that cars don't just pollute the air, but also the water via road runoff and atmospheric fallout. The emerging linkages between air and water quality have got people like Brosseau examining pollution sources outside their immediate spheres of influence. "Air pollution may not be in the universe we control, but that doesn't mean we have to give up. It just means we have form some new alliances," he says.

Many of the pollutants that spew from automobile tailpipes and wear off their body parts attach themselves to fine particles of dirt and dust. "The air people call it 'particulate matter' and we call it 'sediments'. Their medium just happens to sit right above ours," says Brosseau. Though no local data is available, a Milwaukee study estimated that 52-57% of the fine particles on that region's Interstate-94 highway were entering stormwater.

But the stormwater connection isn't the reason this fine dirt and dust hit the headlines earlier this year. The human health connection was. At the time, newspapers reported the results of a Harvard and Brigham Young study of 552,138 people in 151 cities that showed that PM10 (particulate matter below 10 microns in size, or one fifth the width of a human hair) can increase the risk of death from lung damage and associate heart problems by 15% to those living in the cities with the dirtiest air.

Where is the PM10 coming from? Basically from any activity that combusts fuel, disturbs soil, corrodes surfaces or produces smoke and exhaust. Bay Area vehicles left behind 26 tons of PM10 per day in the summer of 1990, according to the local air district, and over ten times that amount gets resuspended (just in case you didn't get to breathe it the first time) by these vehicles daily as they travel the region's paved roads (see chart p.6). An EPA analysis of PM10 trends shows that while the overall amount generated decreased nationwide by 3% between 1983 and 1992, the amount contributed by highway drivers increased from 17 to 26% - a 50% jump attributed largely to an increase in vehicle miles traveled. To Brosseau, this is a "scary" trend.

"It's not good for stormwater because increasing vehicle miles means more particulate matter coming from cars and thus more metals in our air that will end up in our water," he says. Among the myriad possible sources of PM10, vehicles are likely to generate higher concentrations of copper, lead, nickel and zinc. Federal highway administration studies show concentrations of heavy metals are 2-4 times higher in highway runoff than in general urban runoff.

Heavy metals are a primary target of stormwater pollution reduction programs. Indeed the copper contamination problem in South Bay waters has got stormwater officials pointing fingers not just at the car but more specifically at its brake pads. An October 1994 lab analysis of 20 different brake pads done by Woodward-Clyde for the Santa Clara Valley nonpoint program showed their copper content ranged from below detection level (0.00625%) for Ford and General Motors pads to 20.5% for a Volkswagen. Several Japanese models showed up in the middle.

The million dollar question remains how much of the copper (not to mention the lead, nickel and zinc) in the PM10 worn off brake pads ends up in the Bay. Officials say there are far too many variables to get a definite answer to this question right now. But a Woodward-Clyde simulation suggests that 19-75% of the copper in South Bay runoff comes from brake pads.

What stormwater agencies will do about PM10 in general, and their heavy metal components in specific, is still very much up in the air. "Even the best street sweepers can't pick up particles that small," says Brosseau.

On the South Bay copper issue, officials are looking further into the possibility of reducing the heavy metal content of brake pads. The Santa Clara program's Dave Drury says a three-way dialogue is now beginning between his program, EPA and the pad manufacturers. Meanwhile, a new interorganizational brake pad task force may be launched under the auspices of the Executive Council charged with implementing the S.F. Estuary Project's CCMP. The proposed task force would explore potential methods of preventing pad-related impacts and work to educate stakeholders, according to the City of Palo Alto's Kelly Moran. "The Estuary Project offers us a unique and proven structure for regional collaboration, one we county and local folks just don't have," says Moran.

But the larger solution to the PM10 problem - getting people to curb their wanton driving habits - has always been a very unpopular one. Ask Greg Karras about trying to do this and he'll tell you to put your energy somewhere else. In the late 1980s, Karras' organization, Citizens for a Better Environment, collected data pointing out the car as a major threat to water quality. But when that data, and the inevitable need to reduce vehicle miles traveled, were placed before the appropriate regulatory and planning agencies, they all backed away, he says. Since then, Karras has been focusing on easier-to-win fronts of the car-water wars, such as lobbying for cleaner fuels.

"It's not the technical but the political and economic difficulties of radically restructuring our transportation system," he says. "We need to rip up streets, replace autos with mass transit, force companies to locate near their jobs base. In the current political climate, we probably shouldn't tackle this. To solve this problem, we'll need political leadership over generations," Karras says.

In this generation at least, Brosseau is offering a little leadership. He's made some contacts with researchers at the air district to see if they can share data collected and look for linkages. "I think we'll find particulate matter from cars is our common ground," he says.

Contacts: Geoff Brosseau (510)286-0615; Dave Drury (408)927-0710; Greg Karras (415)243-8373 & Kelly Moran (415)329-2421

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