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Continuing Lead saga

If you’ve been following the story you know that the garden and yard at Inye, Kristi, Yirim and Kinneta’s garden is contaminated with lead. We’ve been trying to figure out what to do about it and this post is my attempt to bring things up to date.

In the short term, we’ve built and planted one raised bed with imported, clean soil. More beds are on the way. The raised bed is on top of existing, contaminated soil, so we put a layer of gravel on the bottom, so no one will accidentally dig down and mix the two layers. lead is not very mobile in soils, so the bed should be good for many years.

In the long run we would like to clean the lead out of the yard, but there doesn’t seem to be a good way of doing that, short of digging up the entire yard and hauling it away to a toxic waste dump — way too expensive!!!!!

We looked into growing plants to extract the lead and found that this only works if you add something like EDTA to the soil to make the lead available to the plants. If you do that, the plants suck up lots of lead and you can haul the plants away. After a few years you may have lowered the lead levels enough to be safe.

Only one problem — adding the EDTA makes the lead very mobile, and it leaches into the groundwater!!! For this reason, adding EDTA to soil is banned in all 50 states.

So as of now, we know of no good method to remove the lead from the soil. Question is, then, what are the dangers and how do we deal with them.

IMHO the biggest danger is not that the vegetables will have lead in them — if they did, we could grow vegetables to extract the lead!! Studies have shown that if the vegetables are washed in mild detergent to remove ALL the soil, then the vegetables are safe to eat.

The danger comes from contact with the soil, either by eating it or by breathing the dust. And this is where it gets interesting.

Lead absorption thru the lungs is much more efficient than through the digestive tract. In other words, you absorb more lead if you breath it than if you eat it.

Adults absorb about 30% of the lead we eat. Children absorb more like 50% of what they eat.

I haven’t been able to find exact figures, but lung absorption is closer to 100%.

So here’s the bottom line if you have lead contaminated soil –

1) prevent dust. keep the soil covered with ground cover plants or mulch. Don’t pile dirt where it will dry out and blow around. Don’t track dirt into the house where it will become dust.

2) At least for the concentrations we are seeing in our garden, if your vegie ripens above ground (i.e. not a root vegetable) AND YOU WASH IT WITH MILD DETERGENT, it appears to be safe to eat.

3. If you have small children, get them tested for lead. Its a simple blood test and it will tell you if they have been ingesting or breathing lead. Note that the effects of lead on growing children are very serious and can lead to permanent brain damage. GET YOUR CHILDREN TESTED IF YOU HAVE HIGH LEAD LEVELS IN YOUR YARD.

4) Everybody — get your soil tested. For only $9 you get a test from UMass and you will know if you have lead in your soil (among many other important things).

This next week we are meeting with the Garden Hot Line staff to share information and talk about lead in soils and what to do about it. I will post more then — probably some corrections, so stay tuned.

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