National Pollutant Release Inventory (NPRI) Database Readme
The units of measure depend upon the substance being reported. Generally, release, disposal and recycling quantities are reported in tonnes. However, for substances with alternate reporting thresholds, these quantities are reported in kilograms or grams.
Part 1A - Substances listed at the original NPRI threshold [tonnes]
Part 1B - Metals listed at an alternate threshold [kilograms]
Part 2 - Polycyclic aromatic compounds (PAHs), [kilograms]
Part 3 - Hexachlorobenzene (HCB), Dioxins/furans (toxic equivalent), [grams]
Part 4 - Criteria Air Contaminants (CACs) [tonnes]
Part 5 - Speciated volatile organic compounds [tonnes]
The NPRI data files for all reporting years are available in Microsoft (MS) Access. Environment Canada has published this data as reported by facilities, which includes 'NULL' values. This affects how the information can be accessed and queried; Due to the current structure of the database, queries using Microsoft Access will work correctly only if you are using aggregate functions (e.g. Sum, Count). If you attempt to perform an arithmetic operation (add, subtract, multiply, or divide) you will receive 'NULL' as the answer if any of the fields in your query contains a 'NULL' (highly probable). When using MS Access and attempting to perform an arithmetic operation on the NPRI data, you are required to use the undocumented NZ function (it converts a NULL to a zero) to achieve the correct result to your query (e.g. NZ ([AIRSTA_V]) + NZ ([AIRSTO_V]), notice how each field is encapsulated by NZ. This can lead to very long queries and also severely limits the utility of the built-in query builder.). To perform arithmetic operations, Excel worksheets are recommended since Excel ignores 'NULL' valued entries.
If you have any questions please contact the NPRI Office.
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