TABLE 3. Chemical/Physical Exposure Hazards by Type of Operation (Identified in Prior NIOSH Research).

Operation	Silica	DPMa	VOCsb/BTEXc	H2S	PAHd	Biocides/Misc.e	Metals/NORMf	Flammable	Physical hazardsg
Pad construction	X	X			X			X	X
Drilling	X	X	X	X	X	X	X	X	X
Cementing	X	X	X	X	X	X	X	X	X
Stimulation/fracturing	X	X	X	X	X	X	X	X	X
Well testing/completion		X	X	X	X	X	X	X	X
Well servicing		X	X	X	X	X		X	X
Trucking	X	X	X	X	X	X		X	X

^aDiesel particulate matter and other combustible products (NO_x/CO/SO_x).

^bVolatile organic compounds.

^cBenzene, toluene, ethylbenzene, and xylene.

^dPolycyclic aromatic hydrocarbons.

^eAldehydes, acids, bases, alcohols, surfactants, alcohols, lube oils, and greases.

^fNormal occurring radioactive materials.

^gNoise, heat, and cold.