The EPA continues to replace soil in South Minneapolis. The source of the arsenic was an old pesticide plant that operated from 1938 to 1968. During that time, dust/fumes blew onto several properties in the area. More information can be found in this article.
The article indicates that the levels are very low, but what is a safe level? There is some debate, but I came across the .018 ppb figure in this article. The fact is that arsenic should not be taken lightly. Any level found should raise awareness. Arsenic is prevalent not only in water, but also in soil.