A revolutionary water sensor which tests for pollutants could save lives in Africa, and even help campers in Britain avoid tainted water.

The small piece of paper has been developed by researchers at the University of Bath as a cheap and portable way of making sure people do not drink dirty water.

It was inspired by the litmus paper, which changes colour based on the acidity of water.

The paper test, which weighs less than one gram, contains ultra thin carbon electrodes and a thin layer of ‘electric’ bacteria, which together produce a ‘warning’ signal when exposed to toxic chemicals such as formaldeyde, herbicides such as atrazine, heavy metals or other micro pollutants, such as endocrine disruptors.

As well as helping people in the poorest countries determine if their water is safe, the device could also be used in remote areas in the countryside for people going for excursions or camping in remote areas to check whether a water source is safe to drink.

It could even be used by tourists who are not sure whether their hotel water is safe to drink.