What is the definition of PAHs (polycyclic aromatic hydrocarbons)?
For NPI reporting purposes, PAHs are an aggregate substance group made up of the 16 US EPA Priority Pollutant PAHs (or the subset of those for which data is available) and reported as total PAHs. This list of PAHs and their Chemical Abstract Services Registry (CASR) numbers is provided below.
- Acenaphthene (83-32-9)
- Anthracene (120-12-7)
- Acenaphthylene (83-32-9)
- Benz(a)anthracene (56-55-3)
- Benzo(a)pyrene (50-32-8)
- Benzo(b)fluoranthene (205-99-2)
- Benzo(ghi)perylene (191-24-2)
- Benzo(k)fluoranthene (207-08-9)
- Chrysene (218-01-9)
- Dibenz(ah)anthracene (53-70-3)
- Fluoranthene (206-44-0)
- Fluorene (86-73-7)
- Indeno(123-cd)pyrene (193-39-5)
- Naphthalene (91-20-3)
- Phenanthrene ((85-01-8)
- Pyrene (129-00-0)
Should Total PAHs be reported, or specific PAHs?
For NPI reporting purposes, the amount of ‘Polycyclic Aromatic Hydrocarbons (Benzo[a]pyrene equivalent) (PAHs B[a]Peq)’ emitted refers to the sum of the toxic equivalent amounts of the individual congeners emitted or transferred. Toxic equivalent amounts are obtained by multiplying the mass of the congener by the Toxicity Equivalency Factor published in the NPI Guide.
The NPI defines volatile organic compounds (VOC) as any compound containing carbon that:
- Has a vapour pressure greater than 0.01 kPa at 293.15 K (20 degrees centigrade), i.e., readily vapourises under normal indoor atmospheric conditions of temperature and pressure; and
- Is photochemically reactive, i.e., can contribute to photochemical smog production.
Specifically excluded are:
- carbon monoxide
- benzene hexachloro
- n-dibutyl phthalate
- ethylene glycol
- di-(2-ethylhexyl) phthalate (DEHP)
- 4,4-methylene bis 2,4 aniline (MOCA)
- phenol, and
The inclusion of Total VOCs is in recognition of the combined effect of compounds that contribute to smog formation that may not otherwise have been captured due to individual substances not meeting a usage threshold in their own right. The most common sources of Total VOCs emissions are from the storage and use of liquid and gaseous fuels, the storage and use of solvents and the combustion of fuels. See the NPI Guide for further information.
Should a facility report separately on nitrogen, nitrates and nitrites?
The NEPM for the NPI states that total nitrogen refers only to those amounts of nitrogen that give rise to nitrate/nitrite ions. Since this may be possible for a range of nitrogen compounds in a range of environmental conditions, the following pragmatic definition can be applied:
Total Nitrogen is the sum of nitrate (NO3), nitrite (NO2), organic nitrogen and ammonia (all expressed as N).
Note: Total Kjeldahl Nitrogen (TKN) is defined as organic nitrogen and ammonia, and is determined through laboratory testing.
How should ammonia to water be reported?
Total ammonia to water should be reported as total ammonia nitrogen weight (ammonia (as N, mg/l)).
How should polychlorinated dioxins and furans be reported?
For NPI reporting purposes, total emissions of polychorinated dioxins and furans should be reported as their toxic equivalence (TEQ), which is a means of scaling the emissions of each species of dioxin and furans according to their relative toxicity.