The priority substances indicated in the Environmental Reporting and Disclosure Bylaw, are divided into three groups, A, B and C. The reporting thresholds for each of these groups are different and are listed below.

Toronto Public Health maintains a list of specific health effects for the various chemicals.

Chemical Mass reporting threshold (kg/yr) Concentration Threshold (%w/w)
GROUP A: You meet or exceed the reporting threshold of Group A based on the total amount of priority substance released, manufactured, processed or otherwise used in a year.
Acetaldehyde 100 1.0
Acrolein 100 1.0
Benzene 100 1.0
1,3-Butadiene 100 1.0
Cadmium a 1.0 0.1
Carbon tetrachloride 100 1.0
Chloroform (Trichloromethane) 100 1.0
Chromium, Hexavalent a 10 0.1
Chromium, Non-hexavalent a 100 1.0
1,2-Dibromoethane (Ethylene dibromide) 100 1.0
1,4-Dichlorobenzene 100 1.0
1,2-Dichloroethane (Ethylene dichloride) 100 1.0
Dichloromethane (Methylene chloride) 100 1.0
Formaldehyde 100 1.0
Lead a 10 0.1
Manganese a 10 1.0
Mercury a 1.0 0.0
Nickel a 100 1.0
Tetrachloroethylene (Perchloroethylene) 100 1.0
Trichloroethylene 100 1.0
Vinyl chloride 100 1.0
GROUP B: You meet or exceed the reporting threshold of Group B based on the total amount released, disposed and/or transferred in a year.
Polycyclic aromatic hydrocarbons (PAHs) 10d n/ae
GROUP C: You meet or exceed the reporting threshold of Group C based on the amount that is released. Please note that some Group A substances are VOCs. When you estimate and report your VOCs, be sure to add the amounts of VOCs included in Group A to calculate for Total VOCs.  Also, report VOCs in Group A separately, if they meet the threshold.
Nitrogen oxidesc (NOx) 200 n/a
Particulate matter 2.5 micrometres or less in diameter (PM2.5) 30 n/a
Volatile organic compounds (VOCs), total 100 n/a

a. and its compounds, expressed as the metal
c. NO+NO2, expressed as NOx
d. PAHs release as a result of wood preservation using creosote must be reported even if below the mass reporting threshold
e. n/a = not applicable