Every day, hundreds of trucks criss-cross the Portland region, hauling off the junk people want to get rid of.
But those trucks, as they come to collect your pizza boxes, soda bottles, packing styrofoam and cat litter, can bring some less-than-pleasant stuff to your neighborhood.
"What we've found is that diesel smoke contains particulate matter that, at a micron size, is incredibly devastating to human health," said Matt Tracy, a principal planner in Metro's solid waste management operation.
Tracy said he and others learned a couple of years ago that the particles in diesel were particularly dangerous, in part because the particles don't get caught with dust and other microscopic bits in humans' upper respiratory tract.
"Instead it goes deep into the lungs, where it's introduced in the bloodstream," Tracy said. "It triggers cardiovascular disease and it triggers heart attacks."
With about 1,000 trucks in the Portland region's garbage hauling fleet, Tracy said he and others felt compelled to see what could be done to reduce toxic emissions from the diesel engines.
This isn't merely theoretical. According to some clean diesel advocacy groups, Americans will save $12 in health care costs for every $1 spent on reduction of diesel emissions.
One solution came in the form of a grant from the Environmental Protection Agency, which paid for 58 percent of a program to put filters on the dirtiest of the diesel trucks.
"We put the first filter on a truck in September 2011, and we are putting the final filter on a truck at the end of the month," Tracy said.
Only about 12 percent of the region's hauler fleet – owned by contractors, not Metro – are getting the filters as part of the $650,000 program. Tracy said many haulers are planning on converting their trucks from diesel to natural gas fuel, so there wasn't much of a point in overhauling vehicles with a short shelf life.
Most trucks put in service lately have relatively low emissions, so the program focused on trucks put into service from 2000 to 2007. A little more than half of the trucks had a simpler filter that costs less than $3,000 to install and scrubs 30 percent of emissions. The rest of the trucks got advanced filters that can cost $10,000 each and collect as much as 90 percent of the toxic emissions from exhaust.
The filters have a ceramic core covered in metals that attract the toxic, moist particulates. As the filters heat up, those particulates are burned off, becoming exhaust that is less likely to cause health problems.
The program will cost operators about $300 in maintenance costs for every 1,000 hours of operation, Tracy said.
"These operators have been amazing," Tracy said. About half of the garbage haulers in the Metro region participated; others made their own investments in clean fleets. Waste Management, Tracy said, spent $2 million to put natural gas engines into about 40 trucks.