Miami — Residents in a Broward neighborhood worry that they may be exposed to dioxin, a toxic chemical that can cause cancer and skin disease, and can harm the immune system. For 24 years, hundreds of tons of garbage were burned and buried daily by an incinerator in the neighborhood. The site, now a federal cleanup site after dangerous levels of dioxin were found and neighbors cited high rates of cancer, has recently measured elevated levels of dioxin in the soil. Dioxin levels initially appeared to be low, but the state wants to look further into it. If the Department of Environmental Protection finds that the soil is hazardous, it may have to be dug up and disposed.