HOUSTON (AP) — Houston's lack of zoning restrictions has left many residents with neighbors they don't want: petrochemical facilities and businesses that handle hazardous materials.

That unease was laid bare again last month when a massive explosion leveled a metal fabricating and manufacturing business in the northwest of the city, killing two workers, damaging hundreds of nearby buildings and homes, and terrifying their occupants.

Quan Nguyen, a 49-year-old plumbing, heating and air conditioning technician whose house is a few hundred yards (meters) from Watson Grinding and Manufacturing, sa...