What are the health and safety exposure limits for diesel emissions?

Health and safety guidelines regarding diesel emissions differ depending on the governing body. Mainly focus on two elements; diesel particulate matter (DPM) and nitrogen dioxide (NO₂). In the United States, the Occupational Safety and Health Administration (OSHA) does not specify a limit, for DPM. Manages exposure through general particulate regulations. On the hand the Mine Safety and Health Administration (MSHA) has established a threshold of 160 micrograms per meter (µg/m³), for DMP in underground mines.
 
The permissible exposure limit (PEL) set by the Occupational Safety and Health Administration (OSHA), for nitrogen dioxide is 5 parts per million (ppm) for short term exposure lasting 15 minutes and a time weighted average (TWA) for durations of exposure). The National Institute for Occupational Safety and Health (NIOSH) on the hand recommends keeping exposure levels of diesel particulate matter (DPM) at 1 microgram per meter (µ/m³) to reduce health risks such as illnesses cardiovascular issues, and cancer that may arise from prolonged contact, with diesel emissions. It is recommended to monitor air quality and use engineering measures to ensure compliance with these standards.