Cu L8r, copper and zinc

Where would we be without copper and zinc?

We’re not talking multivitamins here. We’re talking copper water pipes and copper-based treated wood, galvanized steel for fencing, copper-based pesticides for your yard and zinc-based moss killer for your roof. Copper and zinc are all around us, and as Washington grows, so does the use of these useful, ubiquitous metals.

The challenge is that using copper and zinc comes with costs as well as benefits. Copper (atomic symbol: Cu) can harm fish and other aquatic organisms — it reduces the ability of salmon to detect predators. Zinc is likewise toxic to fish and plants (that’s why it gets rid of the moss on your roof).

Copper and zinc are among the most common pollutants found in Puget Sound. So, while no one is proposing getting rid of copper and zinc completely, reducing their use where we can seems like a smart move.

Washington is already a national leader in this work. The state’s 2010 Better Brakes Law paved the way for a national agreement phasing out the use of copper in vehicle brake pads and will eventually keep 250,000 pounds of copper a year out of the state’s rivers and lakes.

That’s one source of copper down. What’s next?

A new study from Ecology’s Environmental Assessment program tries to answer that question. Ecology scientists intensively studied a 7.2-square-mile section of Lacey in south Puget Sound, looking for potential sources of copper and zinc. The sample section, which included warehouses, manufacturing facilities, strip malls, box stores, apartment complexes and ordinary suburban homes, was a good stand-in for the Puget Sound region as a whole.

“This study provides information and tools for future source control efforts,” said Andy Bookter, the Ecology scientist leading the new study.  “The sources of copper and zinc found in this study are similar to the sources found in urban areas around Puget Sound.”

Heavy metal

The nickel version of the report’s findings is that vehicle wear and building materials are the biggest sources of copper and zinc reaching Puget Sound.

“On average, an estimated 800 pounds of copper and 5,900 pounds of zinc are released each year from the materials reviewed in the Thurston County study area,” Bookter said.  “This is from a relatively small urban area with similar land use to other urban areas in Puget Sound.”

Just to hammer the point home: That’s 6,700 pounds of zinc and copper coming off a single, representative 7-mile square sample. Every year.

Vehicle brake wear is still the dominant source of copper — the Better Brakes Law won’t totally phase out copper until 2025, although copper levels in new brakes have already fallen sharply. Roofing materials and treated lumber are other major contributors.

For zinc, moss control is the biggest slice of the pie. We northwesterners seem to wage a constant battle against moss devouring our roofs. The new study’s findings raise questions about the cost of that fight. Other major zinc sources are the siding on homes, car tires and parking lots (parking lots tend to collect all the stuff that washes off of cars — they don’t produce toxics by themselves).

Drip, drip, drip

The new study looked at potential sources. Ecology’s scientists did stuff like talk to roofers about what kind of shingles they were installing, and walk the aisles at garden stores to see which fungicides they sold. To come up with an estimate of the copper or zinc coming off those objects, they took that information and plugged it into calculations like this: 

 OK, so the new study gives us a better estimate of potential sources. The science is sound, but it’s not crazy to want to turn those educated guesses into hard numbers, right?

We’re with you. Along with all of the estimates of how much zinc and copper was coming from where, our scientists also estimated how much uncertainty they had about those numbers. Based on past research, we have a pretty good idea how much copper comes out of vehicle brakes and the zinc running off galvanized guard rails. We are not quite as dialed in on how much comes from your car’s exhaust system, or runs off your deck.

The next step for our Environmental Assessment team is to take a closer look at five sources that we believe to be major contributors to copper and zinc pollution, but ones where we don’t have a lot of real-world monitoring data. Those five sources are:

• Siding
• Chain link fencing
• Roofing
• Gutters
• Streetlights

Our scientists will sample the runoff coming from those potential sources and test it to see how much copper and zinc is in there. That will give us the data needed to refine the other estimates — and eventually help to inform our recommendations about reducing the pollution from those sources.

Save the world — start at home

If you own a home in the Puget Sound region, there’s no need to wait for Ecology’s next study to start making a difference in the health of the environment. And you don’t need to rip up your chain link fence (unless you want to). One good place to start is by using fewer pesticides on your lawn and in your garden. Baking soda is an environmentally friendlier alternative treatment for moss on your roof.

And, if you happen to be buying new brakes for your car, take a look at the box they come in. New brakes should have a leaf symbol on the box — the more leaves that are filled in, the less copper that is in the brakes.

Read the study

• Copper and Zinc in Urban Runoff: Phase 1 – Potential Pollutant Sources and Release Rates
• Poster summary of study findings