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Is there a safe distance for food gardens from Freeways?

Octavius VanZant

Joined: Feb 21, 2012
Posts: 5
I have a large urban lot in Seattle, and at one point I had a very nice vegetable garden going, and I still have 10 nice blueberry shrubs going, and an apple tree.

I'm considering starting up the veggie garden again, and expanding it, but have one concern and wanted some input.

My lot is about 5 blocks east of our city's main Freeway, and I hadn't noticed this until a roofer pointed it out... we seem to get a lot of soot fallout from the Freeway. This fallout is profound enough that roofs darken with time, etc. My ex wife used this as her reason for why she didn't like to grow food at our house.

So my question is, from a toxin perspective, how nasty is this auto-fume-soot fallout? If I were to collect rain water for watering, should I find a way to filter it before using it in the garden?

First time post (just found this site and forum).

Thanks for your feedback.

Tyler Ludens

Joined: Jun 25, 2010
Posts: 5759
Location: Central Texas USA Latitude 30 Zone 8
I think one of the best things to do is to get as much organic material in your soil as possible; this will help promote the growth of beneficial bacteria and fungi which are helpful in rendering toxins in the rainwater into harmless compounds. This actively alive soil will be the "filter" for the rainwater, in my opinion.

Idle dreamer

Octavius VanZant

Joined: Feb 21, 2012
Posts: 5

Thanks. Sounds like adding lots of organic material would be a good idea no matter where my garden is.

I am though, interested in hearing others thoughts about growing food close to, and down wind, of a major freeway. I can see the particulate washout on the roofs in my neighborhood.

What is happening to all of that lead, benzine, and PM10 particulate that collects on the soil and on the foliage of the fruit trees, bushes, and leafy parts of the garden plants?


Hanley Kale-Grinder

Joined: Sep 30, 2011
Posts: 112
Location: Mountain West of USA, Salt Lake City
All of that stuff is probably going to fall on your soil if its falling on your roof. Unless you know the farms that you are getting your food from, the same could be true with anything bought in the store.
Leila Rich

Joined: May 24, 2010
Posts: 3999
Location: Wellington, New Zealand. Temperate, coastal, sandy, windy,
I agree with Hanley: while growing food plants by the motorway isn't exactly ideal, at least you can control how you grow them in those conditons.
Also, as far as I know, heavy metals aren't taken up in most plants, although benzene may be a different story...
I'd be far more concerned about breathing the toxins than eating them. How unhelpful is that
John Polk

Joined: Feb 20, 2011
Posts: 6898
Location: Currently in Lake Stevens, WA. Home in Spokane
Not all of that soot is from the exhaust. There is a lot of 'spent' rubber in there. I used to live a block off of a major highway, and even sweeping the porches every day was not enough to keep the soot out of the house.
Julie Helms

Joined: Dec 06, 2011
Posts: 110
Location: SC Pennsylvania, Zone 6b
Maybe you would be interested in this website:

These gals grow 7,000 lbs of organic produce from 1/10 acre on their urban homestead located 100 yards from an 11 lane freeway in Pasadena. If you search their site you might get some ideas for your situation.
Octavius VanZant

Joined: Feb 21, 2012
Posts: 5

Thanks for the feedback everybody. I'm still cautiously skeptical. I can't really just pick up and move at the moment, and I have the urge to break out the green thumb again this year.

Maybe I'll see if I can have my soil tested from time to time. Just found an organization in our county that will do that.

And thanks for the link to the urban homestead. That is inspirational.

Nicola Marchi

Joined: Sep 20, 2011
Posts: 78
Something I've read several times is that trees and bushes put very little, if any, toxins found in the soil into their fruit.

Depending on the type of pollution you're worried about, using a screen of trees, shrubs, and vines to limit particulates blowing on to your site may work if you have the space.

Whether or not you do have the space, I've read that root crops are generally the least safe to eat in lead polluted soils, so you probably don't want to even think about eating root crops unless you put them in containers.

Another thing to consider is also the amount of contact your vegetables have with the earth. A pumpkin lying on the ground is probably less safe to eat than the peppers you've been growing.
David Wechsler

Joined: Jan 15, 2012
Posts: 9
Location: St. Louis, MO
I think it would be okay to grow food nearby roadways and such as long as you take some active measures to remove the toxins... For example, in a recent reply of mine I touched briefly upon using phytoremediation to remove toxins from the soil.

It would probably be good to grow a high barrier of air-filtering plants as well; see:

And lastly, it may also be a good idea to install a solar-powered fan over your garden area to shuttle-away any airborne particles coming your way in general.

David Wechsler
- Founder,
- Interested in engineering, permaculture, energy medicine, and technology-enhanced ecological systems
I agree. Here's the link:
subject: Is there a safe distance for food gardens from Freeways?