I have always been an avid reader of these forums and have often found them very helpful. For the last years, I used to live in a small flat and all I could keep were 3 tomato plants and two pots of basil in front of a south-facing window.

However, I have recently moved to a semi with a little garden (finally!). The garden is very small, about 100 square feet, and with only a few hours of sunlight a day, but still, it feels like a dream has finally come true!

Unfortunately, the property lies right next to a very busy suburban main road. To top it off, while digging up the trenches for the beds I found a lot of junk that the previous owners must have tossed into the garden, including an old, broken battery.

I discarded the soil all around where the battery was and had samples from various places tested for heavy metal contamination. Yesterday the results came in. I wonder if you could help me out deciding what to do.

The good news is that mercury is below the detection threshold, and arsenic is a lot lower than the average concentration. The bad news is that both Cadmium and Lead are significantly above average, albeit within the limits set by local laws for recycled sludge. All other metals are within average concentration ranges.

My soil apparently contains 52.6 mg/kg Lead and 0.964 mg/kg Cadmium. Nation-wide average values are 30 and 0.5, respectively (on a website, I've found 87 and 0.4 for residential soil, and 32 and 0.3 for horticulture, found in and around Berlin). The legal limits in Germany are 150 and 1.5, respectively, which is a lot more restrictive than the EPA limits in the US, but this is only for sludge, not for the whole soil itself.

My reasoning is that we can't be sure that the veggies we buy at the supermarket would any safer than ours (since it would be legal to fertilise them with even more heavily contaminated sludge, plus chemical fertilisers and pest control), but it's true that, on average, soils used for horticulture have much less cadmium than ours (one third, and that's in the biggest city in the country). I have considered favouring fruiting plants over leaf and root vegetables, but I only get about 4 hours of sun a day, so I'm afraid that's hardly realistic (I do have early peas on right now, but I cannot make a monoculture of them LOL). So I'm afraid I will end up growing lots of nice lettuce, cabbage and spinach too. My wife says she's afraid of touching anything that comes out of that garden (which she has all the right to say, of course).

Do you think I am putting my health at risk here? I must admit I am very reluctant to let go of my dream...

Please excuse the long post and the awkward English, and thank you well in advance for your help.

Lead stays where it is -- in the soil. Crops do not absorb much at all of it. (Unfortunately I can't understand your lab results because they are in a different format, so I'm speaking about a US lead test that came in as well above normal) Even root crops are fine to grow, but they should be scrubbed AND peeled.

It is the ingestion of the dirt that is the problem. If your wife is pregnant or if you have small children, the "safe" levels are much lower than what is considered safe to grow food in. For example, my daughter's lead level in her backyard is 500. Before she was pregnant she could grow and eat what ever she wanted to. But anything over 300 is not safe for a pregnant woman to work in or for a small child to play in (because kids put their hands in their mouths). Some states put the safe level for children to play in at 150.

So your wife can feel safe eating whatever you grow. Definitely safer than commercial food that is grown with municipal sludge. Just peel the outer leaves off of lettuce and cabbage and scrub and peel any root crops. Fruit crops are no problem at all -- just wash them if they fall to the ground.

Raised beds are another good option, but not necessary unless it is the only way for your wife to feel safe about the food you grow -- then they'd be quite worthwhile.
Also, lime and organic matter help make the lead less of a factor.
Keep the garden mulched -- that will keep your contact with the soil to a minimum. (don't want to lead poison you, either!)

In fact, IF lead were absorbed by plants, we'd be able to "clean" up high lead soil by growing plants on them and discarding the plants. This has been tried, but does not work.

I'm writing this in haste -- I hope it has been helpful!
And your English was not the least bit awkward :)

thank you so much for your kind replies. You've all been very helpful.

@kimmsr: Thank you for your encouraging suggestions. I would love to grow lots of fruit crops like tomatoes, bell peppers and squashes, but unfortunately the garden is small, north-facing and surrounded by buildings and fences. With four hours of light a day, tops, and a rather wet climate, I am very restricted in what I can realistically hope to grow. But I will follow your advice and wash everything scrupulously and, as Elisa suggested, discard the outer leaves.

@kimmsr and @jolj: raised beds are something that I'm definitely going to consider for the next growing season. I would feel bad if I had to pull what I already have growing now. But raised beds would surely be a good option for me, because the garden is very shallow (there's only about one foot and a half soil, below that it's rocks). I'll go read up on that topic. Thank you for the tip! I hope I can manage to build something that doesn't look too ugly.

@elisa_Z5: thank you! I really liked your post. First of all, congratulations and best wishes to your daughter. And to you as soon-to-be grandma :oD
We don't have children (yet). But it's true that when I work in the garden, I probably end up inhaling some dust, and also get dirt under my fingernails. I'm definitely going to mulch heavily (and wear gloves). AFAIK the soil has always been lawn until I took over, but the organic content looks pretty high. There are two big trees nearby, you literally cannot overturn a handful of soil without finding a worm, and I do compost a lot. I will lime as necessary.
What units of measurement do they use for lab tests in the US? Here they use mg/kg, which is equivalent to ppm. I'm sure I can find a way to convert. If you have any information about what levels are considered safe for which part of the population, I would be very interested. Here they have some regulations for sludge, but I couldn't find anything for the soil itself.

From what I've been reading around, I believe my main problem is the cadmium. I have found some studies that set my level as the limit between contaminated and non-contaminated soils. Others have the limit at 20, or 30 mg/kg. It would be nice to know if these are just statistical values, or represent a level of actual health risk.

Thank you all again for your precious suggestions. I'm happy there are ways I can still have my veggie garden without putting myself or my family at risk.

JST

The term for planting and discarding plants to clean up soil is bioremediation or phytoremediation.
and uh-oh -- I see that it does work for Cadmium. I think you will want to do more research to see which plants do uptake -- one site I saw said that rice contamination is a concern.

Yes, definitely wear gloves!

Sometimes when a backyard in a city has batteries in it (or in my daughter's case, batteries, pottery shards, broken glass, wire, etc.) it's because the soil was taken from a land fill site to begin with.

Now I'm concerned with the fact that our food system here is sometimes fertilized with municipal sludge with Cadmium in it. Can't seem to get away from these pollutants, can we?

Thank you for the congrats --my son and his wife just gave me my first grand daughter three months ago, and now we're waiting for the second grand daughter. Heaven :)

Best of luck with your garden!

The reason there are different numbers from different states, EPA and other countries is that there are different methods used to calculate safe levels. The mathematical models have numerous inputs, and different authorities will put in slightly different values. Our state, for example, sets a safe level of 260 mg/kg for lead for residential use. EPA uses 400, and ours is lower because we're a heavily lead contaminated state (mining) and there is a lot of actual data on human blood lead levels. Our state health dept. uses inputs from Missouri data.

But 52 is well below ANY regulatory levels I know of. Your cadmium is also well below the standard we use, which is about 17.

A reasonable effort to clean off your veggies will be all you need to do. And don't eat dirt. :-D

I oversee a lot of lead remediation projects. I don't know where these two forces will come to equilibrium, but it will be interesting to watch.

After some research, I have found out that cadmium tends to concentrate in leaves much more than in roots, and only accumulates very little in fruits, if at all. Next time I move, I hope I will have saved up enough for some place with a good sun exposure... Another thing I've found is that, apparently, since zinc and cadmium have the same chemical properties, plants (and animals) deficient in zinc will take up more cadmium. The zinc levels in my soil are in the lower range of average, so I might be tempted to mix some zinc supplements into the watering can (I would prefer to go fully organic, but on the other hand, my heavy metals are not exactly organic to begin with either). If you're worried about the general cadmium levels in your food, perhaps you could ask your doctor/chemist if you can take some zinc pills. Apparently, in moderation they're good for you for lots of reasons.

@toxcrusadr: thank you for your replies. The figures you cite are an order of magnitude higher than mine, so that's indeed a big relief. I wonder if "residential use" also includes keeping a vegetable garden rather than just a lawn and a swing. If so, I think I can feel safe.

I will try to resist the temptation to pop a handful of mud into my mouth from now on LOL. Thank you so much for your knowledgeable posts.

Yes, I believe it does. These risk assessments are usually on the conservative side, so they assume there is a garden, kids playing in the yard, etc.