National Pollutant Release Inventory use in environmental research

Background

Since 1993, the National Pollutant Release Inventory (NPRI) is Canada’s legislated registry of pollutant releases reported by commercial, institutional and other facilities across Canada. The data is publicly accessible, and comprises information on pollutant releases to air, water and land, as well as disposals and transfers of pollutants. Different levels of government use this data to set priorities for environmental management and public health, and to inform Canadians about pollutant releases.

This fact sheet summarizes the use of the NPRI in environmental research based on a scoping review that was conducted to better understand future opportunities for using NPRI data in relevant research areas. The French version of the article can be obtained by submitting a request to the following email address: inrp-npri@ec.gc.ca. This fact sheet gives an overview of NPRI use in environmental research, particularly peer-reviewed literature, from the creation of the program to 2019.

The literature review was undertaken using a set of criteria to select journal articles. Particularly, the articles had to:

1. contain the words “National Pollutant Release Inventory”
2. be publicly available
3. be peer-reviewed
4. be written in French or English
5. be published between 1994 and 2019

The articles meeting those criteria were then filtered, and 225 relevant articles that substantially used NPRI information were included in the scoping review.

Brief history of NPRI use in environmental research

Based on an analysis of the number of articles by year of publication, NPRI-related research first began appearing in the literature in 1997, three years after the first NPRI dataset was published. The number of articles published each year remained fairly low (fewer than four articles per year) until 2002, when an upward trend began, peaking at 31 articles in 2019. Most of the NPRI-related articles were published in English. The analysis also showed that NPRI-related articles were published in 90 different peer-reviewed journals, meaning that the work was reviewed by academic peers prior to publication to limit the risk of errors.

The scoping review also revealed that the NPRI is increasingly being used as a data source for research in a variety of areas from environmental monitoring to socio-economic issues.

The upward trend in NPRI-related articles coincides with changes in the NPRI reporting requirements. For example:

• following the addition of criteria air contaminants (CACs) in 2002 and certain volatile organic compounds (VOCs) in 2003, 47 articles using those specific data were published between 2005 and 2019.
• between 2006 and 2007, the NPRI made changes to the reporting requirements to increase the level of detail in data and reports from certain industrial sectors. These changes contributed significantly to the use of the NPRI in research. The most used data were those from 2006, which was used in 45 papers published between 2008 and 2019.

To learn more about the history of NPRI reporting requirements, visit the NPRI history of reporting requirements.

In addition to changes in reporting requirements, other factors may have played a role in the increased use of the NPRI in research, including:

• growing reader interest in the NPRI as more and more articles were published
• the increase in the abundance of data over time helped create a broader inventory, fostering interest in studying longer time series
• technological advances facilitating access to and navigation of the large datasets in the NPRI, as well as innovative ways to integrate NPRI data into other information sources (for example, the NPRI online search tool, data accessible on the Government of Canada open data portal)
• the promotion of online map layers may have contributed to the popularity of the geospatial analysis theme in research
• growing interest in characterizing the environmental impacts of the oil sands sector contributed to the publication of a large number of research articles that used data from the NPRI
• various promotional activities organized by the NPRI, such as the NPRI Academic Challenge, may have also contributed to this upward trend

What NPRI data is used in research

For more information on the use of NPRI data in research, readers can consult the interactive figures available online in the scoping review.

Environmental compartments of the NPRI

The NPRI collects a large amount of data on pollutant releases, which are categorized according to environmental compartments

• on-site releases to air, water and land
• on-site disposals
• off-site transfers for disposal, treatment, recycling or energy recovery

NPRI data on pollutant releases to the air, the main environmental compartment studied, account for 89% of all articles. Data on pollutants released to water and land as well as disposals were used in the other articles (11%). Some articles (3%) used NPRI data encompassing all the environmental compartments. Data on off-site transfers were not used in any of the studies included in the review.

Substances monitored by the NPRI

Another aspect that distinguishes the studies examined relates to the various substances monitored by the NPRI. CACs, such as volatile organic compounds, sulphur oxides and nitrogen oxides, were among the most widely studied substances. Metals (for example, mercury), polycyclic aromatic hydrocarbons (PAHs), organic substances, polychlorinated dioxins and furans, and hexachlorobenzene (HCB) were also examined.

NPRI data formats

NPRI data are accessible online, and are published in various formats

• single year tables
• five year summaries
• all years datasets (since 1994)
• complete reported datasets.

The NPRI annual data (single year data tables) were the most commonly used format before 2012. After that, longer NPRI data time series were the most widely used format (for example five to fifteen years). Data from 2005 to 2010 and from 2013 were used most often, in 65 articles.

Users of NPRI data in research

The selected peer-reviewed articles included over 800 authors and co-authors, the majority of whom were affiliated with universities, as well as the Government of Canada and the Government of the Untited-States.  Canadian universities, such as the University of Alberta, the University of Toronto, the University of British Columbia and McGill University, represented 38% (over 480 authors) of the publications associated with universities. A total of 40 post-secondary educational institutions in Canada were represented in the NPRI-related publications. The programs of study involved included engineering, biology, chemistry, health sciences, medicine, environmental sciences, geography and forestry.

The Government of Canada and the Government of the United-States were also well represented: Environment and Climate Change Canada (ECCC) and the United States Environmental Protection Agency accounted for the largest number of authors (185 researchers for a total of 81 articles). Some of these authors were affiliated with:

• non-government organizations
• consultants
• hospitals
• industry
• international organizations
• municipal governments
• indigenous groups
• community colleges

Recent publications show that interest in the NPRI is increasing, particularly among universities, federal governments and international organizations in Mexico, Europe and Asia. The broadening of study topics and author affiliations, from a small group of universities and Government of Canada scientists to a broad range of researchers, including those from hospitals, non-government organizations, Indigenous groups and international organizations, indicates that the reach of the NPRI is increasing as well (from a local to a global scale).

Interactive figures are available online and provide further details on authors using NPRI data in their research.

Research topics associated with the NPRI

The most popular environmental research topic is geospatial analysis, which accounts for more than 80% of studies analysed in this scoping review. For example, NPRI geospatial information has been used to:

• quantify exposure to pollutants of interest (e.g. for health) based on the proximity of a given population
• quantify and identify pollutants in a given province or region (e.g. Alberta)
• develop a method for the quantitative assessment of the threat that pollution poses to species at risk

The topic of environmental monitoring was covered in over 60% of studies examined, and was often linked to geospatial analysis, including in situ and satellite observations. Some of the studies that used NPRI data from an environmental monitoring perspective involved:

• monitoring air quality near key facilities in Alberta, with a particular focus on VOCs, particulate matter (PM) and PAHs
• validating environmental monitoring models by comparing different inventories

Predictive modelling is another popular avenue of research (39%): NPRI data were integrated with multiple information sources in predictive models to obtain a variety of findings related to the environment and human health. Predictive modelling was often combined with geospatial analysis and environmental monitoring, as shown by the following examples:

• use of geospatial analysis and predictive modelling to estimate exposure to pollutants
• identification of the most optimal technologies to address air pollution

Approximately one third of the studies (34%) dealt with specific industrial sectors; the majority concerned the Athabasca oil sands.

Other research topics identified include:

• other pollutant release inventories, such as the Australian National Pollutant Inventory and the European Pollutant Release and Transfer Register (18% of articles)
• human health outcomes, for example the rates of hypertension and diabetes in relation to fine particulate matter emissions in Quebec (17% of articles)
• policy or program analysis (11% of articles)
• socio-economic issues (8% of articles)
• treatment and remediation (4% of articles)
• climate change (2% of articles)
• indigenous issues (1% of articles)
• biomonitoring (1% of articles)

Interactive figures are available online and provide further details on the research topics and scientific articles identified in the scoping review.

Benefits and limitations

The use of NPRI data in research has several benefits, including:

• access to a vast inventory of pan-Canadian, georeferenced data on the release, transfer and disposal of over 300 pollutants, most of which have been monitored since 1993
• long-term trend analysis to better understand pollutant releases and their impacts on ecosystems
• identification of environmental priorities on a local or national scale
• informed strategic decision making
• increased monitoring of trends in pollution reduction and prevention

However, the literature covered in the scoping review mentions certain limitations that should be considered when using NPRI data in environmental research, particularly data quality issues and inventory comprehensiveness. For example:

• reporting compliance and uncertainty in estimation methods may cause discrepancies in NPRI reports and measured emissions
• the NPRI substance list does not include all substances of interest for research
• as NPRI data are aggregated only a few times per year, they lack the temporal accuracy required for certain types of research
• the inventory does not include all pollution sources (for example, non-point sources), and it excludes data from Canadian facilities that do not meet reporting requirements.

It is important to consider these limitations when using the NPRI for research. The NPRI takes them into account in its efforts to continuously improve the program. For example, since the inventory was created, a number of changes have been made to increase the comprehensiveness of the substance list and the level of detail for reporting thresholds. Despite the increased complexity of data interpretation, the various changes made have helped increase user interest, as shown by the results of the scoping review.

To learn more about factors to consider in your analyses, visit the guide of using and interpreting data from the National Pollutant Release Inventory.

If you have any questions or suggestions for changes, you can contact us at inrp-npri@ec.gc.ca.

Future environmental research using NPRI data

The scoping review revealed that some NPRI data are under-used in environmental research. New research topics using NPRI data could be considered, such as:

• transfers for treatment, recycling or energy recovery
• data on concentrations in water
• data on certain substances

More in-depth analysis of these data would help us better understand how to improve them for users.

The analysis also suggested other opportunities for projects of interest, such as:

• development of interactive and user-friendly map products beyond Google Earth files (.kmz), such as interactive dashboards;
• establishment of direct links between potential health effects and biomonitoring, predictive modelling, industrial sectors, and policy and program analysis;
• increased knowledge on NPRI compatibility with other pollutant inventories to facilitate future use of the NPRI with those inventories (e.g. the Commission for Environmental Cooperation conducts continental-scale analyses using several pollutant inventories)
• innovative research in the less popular topics identified by the scoping review or other areas of interest, such as:
  • socio-economic issues
  • treatment and remediation of a polluted area
  • climate change
  • Indigenous issues
  • biomonitoring
  • social justice

What can you do now

The NPRI is seeking to encourage broader use of its data. You can help improve the program by sharing your ideas with us at inrp-npri@ec.gc.ca or by collaborating on NPRI awareness and promotion initiatives. The NPRI is also seeking to encourage larger numbers of educational institutions to use its data through the NPRI Academic Challenge, a mentoring opportunity for students which involves working with ECCC pollutant data experts.

For more information, visit our web page named “Partnering and collaborating with the National Pollutant Release Inventory”.