Roadside food - safe to eat?

[orchidee]

We have inherited a brilliant garden from a GGing former resident of Cambridge - even better, there are beans there at the moment that are desperately in need of harvesting!  One problem, it is on what is basically a roundabout on one of the busiest roads in the city - will anything growing here be free from horrible exhaust toxins?!  I have heard a rumour that legumes are possibly the safest things to eat in places like this - any truth in this?

Any advice from experienced GGers? What would you do?!  We really want to eat them, but we are a bit hesitant...

x

[te_3ko]

I personally would not. But it would be very interesting to actually get some hard data on the subject regarding toxin % in regards to population density(or something along those lines).

I keep the edibles away from the roads and busy areas when im planting. As far away as possible

[Egregius]

Personally I wouldn't, but I don't know the hard science on it either. I've read before that fruit trees are relatively safe as they store any toxins absorbed in their woods instead of their fruits, but I've also read vegetables absorb through their skin a part of the pesticides/herbicides they're sprayed with. Where beans stand I don't know (but you can harvest them for seed at the very least )

Myself I've managed to plant some field-lettuce along a busy road. Not gonna eat it!

[Egregius]

I've found some hard science!

In "Preliminary studies on the ability of plant barriers to capture lead and cadmium of vehicular origin"  by  Filippo Bussotti et al, done in Italy, where they tested roadside grasscuttings, topsoil and tree-leaves. Turns out they all contain significant amounts of lead and cadmium, both highly toxic, but there's a strong correlation with distance from the roadside, and number of plantbarriers in between. Note: research done in 1994, more people drive unleaded nowadays AFAIK.

An example: gras growing within a meter from the road had 49 parts lead per million, 2 meters further 25 ppm, 12 meters from the roadside had 8 ppm, and if there's barriers it's even lower.
Soil had much higher accumulations (600 to 40 lead ppm, depending on distance/barriers).

Another indication roadside food should be avoided here.

More reasons not to eat leafy roadside veggies here.

Understanding the routes of plant contamination has been a key focus of the research. Tests across a range of plants revealed heavy metal concentrations to be highest in the plant leaves, followed by roots, fruit, and finally the seed.
The research team established that in leafy vegetables, such as Amaranthus, contamination was primarily via atmospheric deposition, rather than uptake through plant roots. Some of the contamination was in the form of a surface film which could be washed off, but most of the contaminants were found in the leaf tissue.

Crop choice and site selection have been key issues for discussion. Maize, for example, is recommended as safe for roadside cultivation. The grain is protected from exhaust fumes by the outer leaves, and only insignificant amounts of heavy metals reach the grain via the plant roots. Legume crops - such as peas and beans - are also recommended, although the outer pods should not be eaten.

There you have it! Legumes can be safe to eat in one of the more polluted places in Uganda.

(Nuts are 'relatively' safe, and vitamin C intake in general ensures increased resilience to pollutants)

[Bearo]

I asked about this on a general gardening forum with regards to an allotment that I was considering. The advice was that even though there was a risk, the food would still be better than supermarket food with its pesticide content. Not entirely happy with that answer though. I didn't take the allotment.

I'm considering a GG site that I plan to make edible. It is next to a road but only about a car's length. Most of it's length runs along a canal towpath. I'm thinking of planting trees such as conifer to absorb the sound and a lot of the fumes from the road.

I'm also thinking of growing a cleansing crop to draw out the built up toxins that may be in the soil. I believe potatoes do this. Not sure what to do with those spuds after though.

I used to eat blackberries from roadside locations; I never gave the toxins a thought, goodness knows what I've eaten over the years.

[cannonsblazing]

There was a study done in Sweden one or maybe two years ago where lettuce was planted alongside heavily trafficked roads.

I don't remember the specifics, but the conclusion was that you should have a safety distance of at least 20 metres from heavy traffic. It wasn't cadmium and lead so much, but cancer inducing substances that was the problem.

 

[Bearo]

I came across this link  from The London Evening Standard.

[bad.seed]

Even though there is no longer lead in gasoline in western countries, I would be concerned that it has accumulated in the soil as it has nowhere to go. Unless of course the city has cleaned up the soil since leaded fuels were banned, which they probably have not...

I'm looking at a patch around 25 meters from a highway and am feeling ambivalent on whether to proceed with planting or  not. Will e-mail the city and ask about lead in the soils. The site looks great and there's loads of rabbits and mice around (Although these animals would have the highest accumulation of lead of all the living things in the area). The site is close to home and huge (>8600m2), so it looks very nice. I wouldn't grow something I can't eat though.

[TerryLBaker]

Looks like putting inedible organic fences or barriers between the road and your veggies might be the answer for future.  I personally would not eat what is there now.  

[mazzanova]

When you think about it a lot of farmland fields are adjacent to busy roads, even on organic farms. The most toxic area will be it the first 3m from the road edge. There will still be lead etc in this roadside strip. Personnally I do eat roadside wild greens from  verges alongside quiet roads, but only very young ones (up a couple of days or so)