For Clean Air, Work Downtown
In our ongoing quest to discover how land use and urban form links to human health effects, I recently stumbled across something odd. It's a 2000 study of vehicle emissions per household in Puget Sound, authored by Larry Frank. I wanted to find out if there is a connection between air pollution and urban density. According to this study, there is, but in a way I didn't expect.
It turns out that the strongest land-use correlate to low household emissions is not residential density, but job-site employment density. That is, from a statistical standpoint, it matters less whether you live on Capital Hill or the Sammamish Plateau than whether you work in downtown Seattle or Bothell. The difference, I suppose, is that downtown Seattle and other places with high employment density are well-served by transit and are generally easier to get to with lower vehicle emissions than more far-flung workplaces.
Interestingly--this is only interesting if you're a geek; otherwise skip to the next paragraph--the drop in household emissions does not observe a linear relationship with employment density. For the lowest three quartiles of employment density household emissions are about the same (they're a little higher in the lowest density quartile), but then they drop off sharply at the beginning of the highest density quartile. This suggests that there's a threshold of employment density--perhaps the density at which transit, carpooling, etc become viable--after which emissions drop quickly.
Sins of Emissions
Some news bits from the Oregon legislative session, which just ended:
As the Oregonian reports, the auto industry has been trying to head off an Oregon effort to adopt "clean-car" emissions standards by including language in the budget that would effectively prohibit DEQ from implementing the standards. (Clean-car standards, which Washington state just adopted, would reduce greenhouse gas emissions by some 30 percent and help drive the industry toward cleaner, more efficient design.) Governor Kulongoski has promised to counteract the move by using his veto power.
Meanwhile, the industry succeeded in effectively defeating a biofuels bill, which would have provided incentives for in-state production and use of renewable fuels such as ethanol and biodiesel.
Automakers aren't exactly winning points for innovative thinking. From the Oregonian editorial:
The House Republicans who let this happen ought to have to spend the next election explaining why they would trade off Oregon jobs, Oregon agriculture and Oregon innovation all in a futile effort to extend a pollution tax credit and enable the auto industry to keep churning out cars that are less fuel efficient than those they made 20 years ago....
The auto industry has fought every advance -- seat belts, catalytic converters, air bags -- with this same argument about unacceptable costs. Every time its claims have been shown to be wildly inflated and wrong.
And in good news (mostly), the state did win a partial ban on toxic flame retardants known as PBDEs. Our study of PBDEs in Northwest women showed that the chemicals were found in relatively high levels in Oregonians; and a recent study of PBDEs in house dust found that Oregon samples had the highest levels of PBDEs.
