Information for Data Users

Need Help Using, Interpreting, or Understanding the National Pollutant Release Inventory (NPRI) Data?

The National Pollutant Release Inventory (NPRI) provides a number of online tools and resources to help data users make the best use of NPRI data in analyses:

Still need an answer to your question? Contact the NPRI directly!

Guide for using and interpreting NPRI data

The NPRI program makes a significant amount of information available, including facility-reported data on pollutant releases and transfers, latitude and longitude and other location data for reporting facilities. Please keep in mind the following considerations when using and interpreting NPRI data:

General Considerations
  • The NPRI is a key tool for identifying and monitoring sources of pollution in Canada, but it does not provide information on all pollutants or every source of pollution in the country.
    • Some substances of concern are not included in the NPRI. For example, the Government of Canada tracks greenhouse gas emissions through a separate program (see the Greenhouse Gas Sources and Sinks website for more information).
    • The NPRI collects information only from industrial, commercial, institutional and other facilities that meet certain reporting requirements. These reporting requirements are based on the number of employees at the facility; the quantity of the substance(s) manufactured, processed, used or released and the type of activities performed at the facility. (For more information on these reporting criteria, see the NPRI Reporting Tools and Guidance.)
    • Many small facilities are exempt from reporting, as are facilities in certain sectors (e.g. car repair shops and fuel marketing stations.) However, air emission summaries for criteria air contaminants, heavy metals and persistent organic pollutants from all Canadian sources are compiled and made available annually by Environment Canada (See Air Pollutant Emissions for more information.)
    • Additional information on NPRI reporting coverage is available from the links below: 
    • Some of the pollution in Canada originates in other countries. This phenomenon is known as transboundary pollution and it is a significant source of smog-forming air pollution in certain areas of Canada.
  • Not all pollutants are equally hazardous.
    • Identification of risks to human health and the environment from pollution is complex and cannot be determined from NPRI data alone. Environment Canada and Health Canada continue to assess the health and environmental risks of chemical substances.
    • A pollutant's potential to cause harm to human health and the environment depends on a variety of factors, including its inherent toxicity; whether it is released to air, land or water; if and to what extent it is broken down in the environment; and the resulting amount, nature and level of exposure.
  • Environment Canada implements a number of measures to ensure the quality of NPRI data in order to maintain a high standard of accuracy, consistency and comprehensiveness, and to continue to meet the needs of data users. Please consult the data quality page for more information.


Facility-Reported Data

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  • NPRI reporting requirements have evolved over time to provide more comprehensive information on pollution in Canada. Substances have been added, thresholds (limits) at which substances must be reported have been reduced, and exemptions for several industry sectors have been eliminated. These changes to NPRI reporting requirements need to be taken into account when conducting year to years trend analysis based on NPRI data.

  • There are a variety of reasons why facilities may report different amounts of pollutants that they release, dispose of or recycle from year to year. These reasons range from new reporting requirements (as highlighted above), to changing production levels, facility expansions and process modifications. Reported data may also be updated from time to time as new or more up-to-date information is received and reviewed.

  • Adding quantity values reported by different facilities may result in errors in interpretation. For example, this may occur when a facility generates pollutants and transfers them to another site to manage disposal, which then transfers them to a third facility for disposal. In this case, "double-counting" of the off-site disposal may occur between the originating facility and the second one.

  • Total reduced sulphur consists of 6 substances. Three of these substances (hydrogen sulphide [H2S], carbon disulphide [CS2] and carbonyl sulfide [COS]) are also listed individually in the NPRI substance list. When conducting analysis of NPRI data, caution should be taken to avoid "double counting" of total reduced sulphur and these individually-listed substances.

  • Facilities may use different methods to determine how much of a particular substance they release, dispose of or recycle. These methods may vary depending on the substance or the facility and may also change from year to year. Estimation and direct measurement are examples of these methods.


Tailings and Waste Rock Data

The following are important considerations for the use, analysis and interpretation of National Pollutant Release Inventory (NPRI) data on tailings and waste rock (TWR) : 

  • Increases in reported values related to tailings and waste rock are primarily due to a change in NPRI reporting requirements

    The difference in the amounts of NPRI substances reported for 2005 as compared to 2006 and more recent years are mainly due to changes in NPRI reporting requirements related to substances contained in tailings and waste rock.  The reader should also note that these substances are reported to the NPRI as “disposals” and not “releases” as they are contained within managed disposal sites and are not being released directly into the environment. Direct releases to air, water and land from mining facilities were required to be reported previously.

  • Direct releases of pollutants pose different risks compared to managed disposals

    Risks to human health and the environment from pollutants vary significantly depending on whether they are released directly to air, water or land, or disposed of in a regulated landfill, tailings impoundment, waste rock management area or other disposal area. For example, direct releases of mercury pose a greater risk than mercury contained naturally in low concentrations in rock removed during mine operations and disposed of in a permitted area for long term storage and management.  

  • Tailings and waste rock data for Canada and the United States are not directly comparable.

    Data on tailings and waste rock are not directly comparable for Canada’s NPRI and the U.S. Toxics Release Inventory (TRI). The two programs have different reporting requirements, thresholds, exclusions and substance lists. In addition, some sub-sectors in the U.S. (e.g. iron ore, uranium, potash) are not required to report to TRI. Consequently, quantities of substances in tailings and waste rock reported to the NPRI and TRI may be different even for very similar facilities.

  • Facilities are required to report the concentration of NPRI-listed substances in tailings and waste rock. They also have the option of providing additional comments about the specific substances they report on.

    This information is available by searching for an individual facility on the NPRI Online Data Search, and then viewing the report for a specific substance. 

  • Differences in geology explain many of the different values reported by similar facilities.

    The reported quantities of NPRI substances in tailings and waste rock generally reflect naturally-occurring substances in the rock or bitumen deposits removed and/or processed by mining facilities. As a result, differences in the quantities of substances reported for disposal by facilities may reflect differences in geology and in the type of mineral deposit. 

    For example, consider two facilities with similar production levels and environmental management practices. A facility located in an area where the rock contains a naturally high level of arsenic would be expected to report larger amounts of that substance for disposal, compared with a facility in an area with lower levels of the substance.

  • Certain exclusions apply.

    Certain materials are exempt from reporting to the NPRI for tailings and waste rock. These include inert waste rock, sand in tailings, and materials used as structural components, for example, to build roads and dams. For more information on exclusions, please refer to the Guide for the Reporting of Tailings and Waste Rock to the NPRI.

  • Facilities may report negative values for substances contained in waste rock or tailings.

    The disposalof mined materials in a waste rock or tailings management area is not necessarily a final disposal. For example, if market prices increase for a given metal or mineral, it may be profitable for a mining operation to “mine” or process materials previously disposed of as waste rock or tailings. Reporting of a "negative number" for waste rock or tailings indicates that the quantity of a substance removed from the management area exceeded the quantity of the substance deposited in that area for a given year.

  • A number of government and industry initiatives are in place to manage potential environmental concerns from tailings and waste rock.

    Specific initiatives include the Metal Mining Effluent Regulations, the Environmental Code of Practice for Metal Mines, the Mine Environment Neutral Drainage Program and the National Orphaned/Abandoned Mines Initiative.

    For more information on these and other initiatives, please see the NPRIrelated links page.  
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