Is diesel emission exposure monitoring & reporting a legal requirement for businesses?

Certainly!
It is mandatory, for businesses operating in industries with risks such as mining and construction to monitor and report diesel emission exposure as per legal requirements enforced by regulatory bodies like HSE in the U.K. Companies are obligated to control and reduce worker exposure to diesel emissions in compliance with strict regulations particularly in industries, like underground mining where monitoring of diesel particulate matter (DPM) levels and record keeping are essential to meet exposure limit standards.