A few years ago my brother-in-law wanted to start a vegetable garden in the backyard of their Boston home. My sister was pregnant and he wanted to bring some pesticide-free vegetables to the table and (eventually) teach my little niece about photosynthesis, bugs and composting. But his uncle, a chemist, was worried about the quality of the soil given their urban environment, so he took a sample and had it tested in his lab. And the results were extremely worrisome...
The lead content in their backyard soil was at dangerous levels — completely unsafe for growing food and especially for feeding that food to a toddler! Uncontaminated soil levels of lead are typically around 10 ppm. My sister and brother-in-law's lead count for top soil was 454 ppm (parts per million) and for 2" deep soil was 1003 ppm. When he first had the idea of starting a garden, my brother-in-law figured he'd have to work to amp up the nutritional content of the soil, but he never imagined that the soil would actually be dangerous to his health and the health of his family.
The New York Times wrote an article on this very topic a couple weeks ago. Health officials, soil scientists and environmental engineers are cautioning against urban gardening due to the high levels of lead in many urban backyards. Where does the lead come from? It can leech into the soil from paint that's been scraped off houses, old lead plumbing or lead pesticides. In my brother-in-law's case, his uncle surmised his problems were the result of Boston's heavy traffic and years of leaded gasoline and car exhaust.
If you currently have a backyard garden or are planning one, you should have your soil tested first. Check with your local health department or local university (usually in the Environmental Sciences department, or something related). A google search in your area under "soil testing" should bring up some good results. Here are a few testing resources we know of offhand:
Brooklyn College Environmental Sciences Analytical Center: Cost is $20 for a soil analysis.
EarthCo: online soil testing company. Cost is $25.
If your soil is found to have a high lead content, experts recommend covering it it with sod. According to The New York Times, if you're planning on growing edible crops, you can replace the contaminated soil or alkalinize it with lime or compost (although that's unlikely to help that much if your lead level is particularly high). You're better off building raised or contained beds, or starting a container garden, as my brother-in-law did.
Read the whole article at the The New York Times.
Have you had any experience with lead in your garden?