### How Far Should You Live From A Road To Avoid Pollution?

A seemingly rarely talked about problem is pollution from cars and trucks affecting commuters and people who live and work near major roadways. There are many publications on this, but I could not find one that aggregated information cleanly so I put this together.

#### How far does roadway pollution travel?

First, it depends on many factors. What type of pollution? What is the road type? What is between you and the road? What direction is the wind blowing? There's no single answer to this question. However, you can get a pretty good idea from looking at some of the plots available.

One nice summary plot comes from this publication concerning freeways in Los Angeles:

The negative distances are upwind and the positive distances are downwind. UFP stands for 'ultrafine particles'. This is quite alarming. Downwind, there is still significant pollution 2500 meters away from the roadway. That's more than 1.5 miles. Further, the pollution level doesn't drop to 50% of the value at the road until you get ~500 meters (more than 0.3 miles) away. In many cities, it is difficult or impossible to get that far away from a major roadway. For reference on that distance, I have included it for Mopac Expressway in Austin (where I live) The green tinted region below is roughly 500 meters on either side of the freeway in the middle:

You don't have to be familiar with that area to get an idea of how far that is...just count the number of neighborhood roads, consider that it's a normal neighborhood near but not in the downtown area of a decently large city, and convert it to your city. If you would like to see this for a specific location, just go to google maps, right click, and measure distance.

Another nice summary plot comes from an EPA report that broke this out by particle type:

You can see from this that some particles drop off rapidly, some drop off slowly, and some showed no significant decline within 400 meters of the road.

A third nice summary plot comes from a study carried out in Oakland that separates by particle type and plots vs distance to nearest major highway:

Similar trend. The decay rate varies by particle, and the pollution is measurable hundreds or thousands of meters from the nearest highway.

#### How far from roadways are health effects observed?

Instead of measuring particle concentrations directly, another way to measure this is by health effect.

This report took data from this report and showed the relationship between asthma incidence and the distance between your home and a major road:

That second report has a cool plot showing roughly that above plot but split by how long someone lived in that location. Plot A is children that lived by the road since before they were 2. Plot B is children that moved by the road after they were 2:

Another study found that wheezing episodes were more common in children with longer commutes to school.

A study on residents of Ontario found that rates of dementia increased the closer you lived to a major road all the way out to 300 m, and was highest among people who lived near a major road, in an urban area, and lived there for an extended period.

A study on older women found that COPD was much more common among women living <100 m from a major road than women living >100 m from a major road.

A study on children in California found that growing up within 500 m of a major road had significant detrimental effects on lung development.

A study on children in California found that they were more likely to develop autism if their mothers lived within 1000 feet of a freeway during the third trimester.

study on older women found that proximity to a major roadway was highly correlated with prevalence of hypertension:

It is worth noting here that I have talked about air pollution so far, and this effect at least might be related to noise pollution as noise pollution is associated with heart problems (another).

There is much more research out there. If you search for it (you can use the EPA link from earlier as a good starting point), you'll find that at least the following occur more often in people living near major roads:
• lung disease
• heart disease
• pregnancy/birth complications
• some cancers (particularly leukemia in children)
• dementia

#### What lowers the risks?

If you check that EPA link from earlier, there are some nice plots. I won't go into detail as this is already getting a bit long, but noise barriers help, trees help, being upwind from traffic helps, and road design helps (e.g., depressing roads). For example, having a tall noise barrier and a forest between you and the road roughly halves the pollution levels at a given distance from the road.

Also, as is obvious from common sense and from the information above, being further from the road helps.

#### So should I buy a house near a road?

There's no simple answer. For one thing, even if you live far from a road, you have to work somewhere so your workplace and/or school need to be far from major roads. Also, living far away from everything generally increases your commute, and all these same problems occur with long commutes. The ideal would be telecommuting far from a road in a sparsely populated area, but that describes very few of us.

Consider all the evidence here, and factor it into your decisions. I personally would not target anything within 300 meters of a major roadway, and would still have it as a factor beyond that but it would be less important than others. I would also try to avoid densely populated and heavily trafficked areas in general, but that is very difficult to do.