How far do you need to be from a busy highway to grow edible plants?

February 26, 2013 5:49 PM

Looking around at houses for sale in a high-traffic area (NYC suburbs). I-95 runs through all of the towns. What's the minimum distance I'd want the property to be from 95, in order to grow an edible vegetable garden (in raised beds)?
posted by xo to Home & Garden (8 answers total)

If you want to raise edible crops and soil quality/toxins are important to you, you'll want to test the soil of any house you buy. There are so many other sources of pollution that are much less obvious. For instance, I have a friend who lived near an old, dirty (shuttered) factory and she had to do a lot with her soil to make it safe - she lived miles from a freeway.
posted by lunasol at 5:52 PM on February 26, 2013 [3 favorites]

I'd be more concerned about not being downstream from the highway runoff than actual physical distance from the highway.
posted by dabug at 5:58 PM on February 26, 2013 [1 favorite]

Just another anecdote, 495 (also known as the Long Island Expressway also known as the world's longest parking lot) along with many other major roads run through Long Island's vineyards and apple orchards. I'm not dead yet (though I am more of a beer drinker).
posted by Brian Puccio at 6:41 PM on February 26, 2013

If lead (from tetraethyllead) is your main concern, you should just test the soil and not worry about distance from the highway. Generally, if you are looking at property with one or more buildings which were painted at any point before 1978, the year residential lead paint was banned, it's much more likely that the lead in your soil comes from paint flakes anyway.

If you're testing the soil at a property you're considering, take the samples from where you would locate the garden. Lead contamination levels can vary considerably even over an acre or two, because it isn't super mobile once it's in the soil, though this is of course the same reason you need to worry about 30+-year-old lead contamination from leaded gasoline and paint.

If you aren't worried about lead, can you post a followup to let us know what kind of pollution you're concerned about?
posted by pullayup at 6:51 PM on February 26, 2013

Agreed that airborne lead is (thankfully) no longer a concern from roadways, especially if you're putting in raised beds rather than using the historic soil. Raised beds with clean soil should be pretty safe. Yes, there will be slightly more deposition of PAHs from the highway if you're quite close to it, but as far as I know, they aren't taken up into plants very readily. So if you use raised beds and wash your produce, you should be in good shape.

On the other hand, if anyone in the family has problems with asthma, there's a pretty good correlation between distance from major roadways and asthma incidence. It falls within a quarter mile, maybe? You should be able to find more information on-line or through your department of public health.

That said, test the soil, regardless. Agreed with the above that house paint and other historic sources aren't always obvious (and that purchased soil isn't always pristine). Lead is the big one to watch for (opinions vary, but there is a fair bit of literature showing it gets taken up in plants). The test shouldn't be expensive. Also, note that your soil may not be pristine, because no soil is, including agricultural fields. So if your lead is below 100-150 ppm and there are no other red flags, enjoy growing and eating healthy fruits and vegetables!
posted by ldthomps at 7:09 PM on February 26, 2013 [1 favorite]

When the National Zoo solicited emergency bamboo donations, their threshold was 100 feet.
posted by djb at 7:52 PM on February 26, 2013 [2 favorites]

According to the good people at Cornell:

It should be emphasized that the amount of lead taken up by plants for the most part forms a negligible input into our total diets. Even in soils with fairly high lead levels, much of it cannot be taken up by plant roots and is naturally excluded. However, lead-contaminated soils can be a greater health hazard directly to young children than eating vegetables grown there. Ingestion of lead-contaminated soil through hand-to-mouth activities can cause a significant problem. Also in this same regard, any soil adhering to plant leaves, roots or fruits should be meticulously washed off if the soil has been found to be high in lead.

posted by pracowity at 11:38 PM on February 26, 2013 [2 favorites]

Tire dust is my reason not to garden right beside the interstate. It contains cadmium and a few other metals and coats everything with a fine black dust. I don't know if plant uptake is a concern with cadmium but you will certainly need to wash the heck out of your vegetables (that is also the main threat from lead in soil - dust accumulating on leaves). Once you do that they should be safe.

Here is an article.
posted by ChrisHartley at 4:48 AM on February 27, 2013