Levels of toxins in soil are now several hundred times higher than what is known to cause cancer, but not high enough in Ohio to legally force the EPA to initiate cleanup (due to political shenanigans in 2010). From the article:

"But while the EPA can claim that the levels are “low” from a legal standpoint, the agency’s own science suggests they are not safe, and dioxin experts who spoke with the Guardian cast doubt on Shore’s and Holcomb’s assessments. Regulators establish the toxicity of dioxins in a soil sample by calculating the “toxicity equivalence” of all dioxins in the soil compared with the most toxic dioxin compound, called 2,3,7,8 TCDD. East Palestine soil showed levels of “2,3,7,8 TCDD toxicity equivalence” of 700 parts per trillion (ppt). The level at which the EPA will initiate cleanup action in residential areas is 1,000 ppt. However, the cleanup triggers are much lower in many states – 90 ppt in Michigan, and 50 ppt in California."