Though lead-based paint and leaded gasoline are now illegal, they continue to taint the land in many US cities. Soil researchers tested soil from urban gardens in Indianapolis, finding nine out of 10 with high lead content in the soil. Boston even had problems with trucked-in soil, which was contaminated by windblown dust and dirt. While most plants do not draw lead up from dirt, agriculture experts advise urban gardeners to have their soil tested as a precaution, saying that it is most dangerous when soil gets indoors or on food that is not thoroughly washed. Currently, there are more than 2,600 active urban gardens in the US, yet no standard practices for urban agriculture.