Per the USA Today report published in December 2008
EPA modeling and subsequent air monitoring revealed the presence of carcinogens and heavy metals in close proximity to schools around the country. “It is meant as ‘a screening tool. It isn’t an in-depth analysis,’ says Nick Bouwes, who helped create the model for EPA” and should not be used to estimate risk. It should be noted that the data represents air quality outside of the schools and only thorough sampling inside the schools can document the indoor air quality.
Read more HERE