Well, this is a bit scary when you consider the compost is going into organic gardens…

As thousands of cities have begun composting yard waste and hundreds more begin collecting food scraps on a large scale, new questions are emerging about what kinds of things make their way into compost and whether any of them pose a threat to humans and the environment. Federal laws do not require compost to be screened for contaminants, of which plastic and glass are only the most visible. Random tests of compost used in organic agriculture have occasionally turned up elevated levels of lead and traces of pesticides. Last month, the US Composting Council, the industry’s trade group, warned its members to watch out for grass clippings laced with Imprelis, a new weed killer from DuPont that does not easily break down in compost piles.

http://www.motherjones.com/environment/2011/06/are-there-toxins-your-compost