Every property in a small Western Australian town is to be tested for lead residue, amid fears the area is widely contaminated with the toxic substance.

Northampton's 870 residents have been told a team of inspectors will screen the entire town from July, after lead was discovered in properties two years ago.

It's suspected lead tailings or waste product from a former mine processing plant in the Mid-West town may have leached into a nearby creek almost 30 years ago.

Northampton resident Mary-Kate Walsh says she is extremely concerned for her family's safety.

"The fact that they are sampling every block of land, every home and site and waterway, it sounds like there is quite an issue there," she said.