In the late 1980s, an area of the Jurupa Valley in Riverside, California began a transformation that would turn it from a community of sprawling dairy farms to hub for enormous warehouses. David Danelski, then an investigative reporter for the Riverside-Press Enterprise, unraveled the details through public records on town planning and found one important document missing from projects approved by county officials for more than a decade: the environmental impact statement. Here are his tips on this and other key records requests you can file.

Freelance journalist Monica Vaughan was reporting on air pollution in California’s San Joaquin Valley when the words of one mother changed her perspective. “I just scan the stories looking for the sentence about whether or not it’s safe to live here. And I can never find that,” Vaughan remembered the woman saying.

In a second guide on air pollution, we bring together advice from reporters like Vaughan and examples that might help you uncover unsafe air in your community. From intial complaints to sustained violations, we give you the tools to ask your local government how it regulates polluters in your area

In 2004, Dina Cappiello discovered some Houston residents were exposed to cancer-causing toxins at a level 20 times higher than federal guidelines — for toxic waste dumps. “Everybody was like ‘nothing to see here,’ but I was like something doesn’t add up,” Cappiello said. In this guide, we share tips and examples from Cappiello and other reporters of what you can request in your community to understand how dangerous the air is and even pinpoint potential polluters.

Breakthrough data by occupation was released by the Southern Nevada Health District after an open-records request. Here’s how you can find the same thing in your state.