Drivers who don't use windscreen was fluid are at greater risk of contrating legionnaires' disease. 

Health experts have discovered that windscreen washer fluid reservoirs are perfect breeding ground for the bacteria, which is found in warm, stagnant water. Professional drivers are at greater risk because they use their windscreen washer more often. The spray produced by the washers can enter air vents leading drivers to be exposed to the legionella bug.

Up to 20% of legionella cases could be attributed to windcreen washer water the study found. The UK Health Protection Agency-led study revealed most at risk were found to be those driving a van, people who drive through industrial areas, and people who often had the car window open but the highest risk group were those not using windcreen washer additive, which is effective in killing the bacteria.

The report indicated adding washer fluid "may be of worldwide relevance in reducing morbidity and mortality from legionnaires' disease."