Using and Understanding the Data
Data from the three countries' PRTRs were retrieved by the CEC from the three governments or from their publicly accessible websites. The CEC received the data for this year's edition of Taking Stock from Canada and the United States in February 2008 and from Mexico in May 2008.
The data sets of the national PRTR systems are constantly evolving as facilities revise previous submissions to correct reporting errors or make other changes .
Scope and Methodology
The methodology used in preparation of the annual report and online database includes the following :
- As of the 2005 reporting year, the scope of the data has been expanded to include all data reported to the three PRTR programs.
- The PRTR data from each country are compiled and integrated into our database. This involves standardizing data fields used in the three countries-for example, aggregating off-site transfers to disposal (NPRI) into an "off-site releases" category to make the data comparable (see "Glossary of Terms").
- Certain individual reported substances are aggregated into pollutant groups or categories (e.g., a specific metal and its compounds). In these cases, no specific CAS number for the pollutant is assigned.
- The data are submitted to a general review in order to identify inconsistencies or possible errors, which are then communicated to the national PRTR programs. Although the CEC cannot be responsible for erroneous reporting by facilities, it's our goal to use the best data possible.
- Data for each reporting year (going back to 1998) are refreshed at least annually - a fact you are urged to remember, particularly when attempting to use this data to analyze time trends. You can visit the national websites to view any changes to the data.
- For the special feature on the petroleum industry, data from the US National Emissions Inventory were used to supplement PRTR data for certain petroleum subsectors. As a result, the analyses in the feature chapter cannot be easily replicated using the online data search tool. However, PRTR data reported by petroleum industry facilities can be searched in the database.
Features of North American PRTRs
Taking Stock is based on information provided by North America's three national PRTR programs. Each country's PRTR has evolved with its own list of pollutants, industrial sectors and reporting requirements. The table below compares features of the North American PRTRs.
Feature |
US Toxics Release Inventory (TRI) |
Canadian National Pollutant Release Inventory (NPRI) |
Mexican Registro de Emisiones y Transferencia de Contaminantes (RETC) |
First reporting year |
1987 |
1993 |
2004 |
Industrial activities or sectors covered (as of 2005)
|
Manufacturing and federal facilities, electric utilities (oil- and coal-fired), coal and metal mines, hazardous waste management and solvent recovery facilities, chemical wholesalers and petroleum bulk terminals |
Any facility manufacturing or using a listed chemical, except for exempted activities such as research, repair, retail sale, agriculture and forestry. Mining extraction activities were exempt for 2004 reporting, but have been added for 2005 and later years. |
Facilities under federal jurisdiction: petroleum, chemical/petrochemical, paints/inks, metallurgy (iron/steel), automobile manufacture, cellulose/ paper, cement/limestone, asbestos, glass, electric power generation and hazardous waste management. Other facilities with specific activities, such as the transfer of hazardous wastes or releases of wastewater to national water bodies. |
Number of pollutants subject to reporting (as of 2005) |
About 600 pollutants |
Over 300 pollutants |
104 pollutants |
Employee threshold |
10 or more full-time employees (or equivalent) |
Generally 10 employees or more. For certain activities, such as waste incineration, wood preservation and wastewater treatment, the 10-employee threshold does not apply. |
No employee thresholds |
Chemical "activity" (manufacture, process or otherwise use) and release thresholds |
"Activity" thresholds of about 11,340 kg (with an "otherwise use" threshold of about 5,000 kg); lower thresholds for persistent bioaccumulative toxicant (PBT) chemicals; lower release thresholds for pollutants such as dioxins and furans |
"Activity" thresholds of 10,000 kg for most chemicals, but lower for PBT chemicals; lower release thresholds for polycyclic aromatic hydrocarbons, dioxins and furans, and criteria air contaminants |
Release and "activity" thresholds for each chemical (facility must report whether it is meeting or exceeding either threshold). Release thresholds range from 1 kg to 1,000 kg. "Activity" thresholds range from 5 kg to 5,000 kg. Dioxins and furans must be reported for any "activity" or release. Any release of polychlorinated biphenyls (PCBs) and sulfur hexafluoride is reportable. |
Types of releases and transfers covered |
On-site releases to air, water and land, and underground injection; transfers off-site to disposal; recycling, energy recovery, treatment and sewage |
On-site releases to air, water and land, and disposal, including underground injection; transfers off-site for disposal, treatment prior to final disposal (including sewage); recycling and energy recovery |
On-site releases to air, water and land; transfers off-site for disposal, recycling, reutilization, energy recovery, treatment, co-processing (input from another production process) and sewage. Underground injection is not practiced in Mexico |
Which Pollutants Must Be Reported?
Each PRTR system covers a specific list of substances of concern:
- NPRI spans over 300 pollutants
- TRI approximately 600
- RETC 104.
As of April 2006, the Chemical Abstracts Service (CAS ) listed more than 27 million chemical substances and identified more than 239,000 of them as regulated or covered by chemical inventories worldwide.
In general for NPRI and TRI, a facility must report if it manufactures, processes, or otherwise uses 10,000 kilograms (NPRI) or 11,340 kilograms (TRI) of a listed pollutant .
Mexico's RETC has both an "activity" threshold and a "release" threshold (i.e., the amount of chemical released during the year). A facility must report if it meets or exceeds either threshold.
Generally, the "activity" threshold is typically either 2,500 kilograms or 5,000 kilograms, depending on the substance; the "release" threshold is 1,000 kilograms.
List of common pollutants
Categories of PRTR pollutants
- Known or suspected carcinogens (IARC)
- Known or suspected developmental or reproductive toxicants (California Proposition 65 list)
- Metals: Metals occur naturally, but particular human activities such as mining and smelting enlarge the proportions of metals in the environment. The toxicity of metals and their compounds (e.g., chromium, nickel, arsenic, cadmium, lead and mercury) depends in part on the forms they take in the environment. A number of metals are considered to be persistent, bioaccumulative and toxic (PBT) substances, which have properties that render them a long-term environmental and health threat, even in small quantities.
Toxic Equivalency Potentials (TEP) for Air and Water Releases
Toxic Equivalency Potentials (TEPs) indicate the relative human health risk associated with a release of one unit of a pollutant, compared to the risk posed by the release of one unit of a reference substance. The reference chemical for carcinogens is benzene and the reference chemical for recognized developmental and reproductive toxicants is toluene.
TEPs provide a chemical ranking system that takes into account both a chemical's toxicity and its potential for human exposure. However, this analysis is limited in that a release does not directly correlate to actual exposures, nor to levels of risk. In addition, not all of the chemicals have an assigned TEP (information on their toxicity or exposure potential may be missing). While these chemicals are not ranked by TEP, they should not be assumed to be without risk. Also, TEPs for land releases are not available; therefore, some potentially high hazard chemicals with these types of releases will not be ranked by TEP.
The TEPs used in Taking Stock are provided at the Scorecard website, and are one of many different screening tools, each of which is based on a series of assumptions. Therefore, different screening tools yield different results.
Taking Stock provides TEPs for:
- Known or suspected carcinogens (for air and surface water releases)
- Developmental or reproductive toxicants (for air and surface water releases)
The TEP is multiplied by the amount of release and the result is used to rank the pollutants. If there is no TEP for a particular substance, no rank is given. To view the TEPs for pollutants released to air and water, click on the TEP button.
Note: Assessing potential harm to the environment from particular releases of a pollutant is a complex task, because the potential of a substance to cause harm arises from various factors, including its inherent toxicity and the nature of the exposure to the substance (e.g., the potential risk posed by asbestos sent to a secure landfill is considered to be much lower than the risk posed by asbestos released to air). However, the data and information reported about a pollutant's chemical properties and toxicity can serve as a starting point for learning more about its potential impacts .
The following sources can provide additional information:
Which Industries Report ?
The three countries have adopted the North American Industry Classification System (NAICS), whose codes are used to categorize the industrial activities of a facility.
Manufacturing industries
These include the large variety of activities listed under primary NAICS codes 31-33, which produce, among other things:
- Food and beverages
- Textiles
- Pulp and paper
- Chemicals and plastics
- Primary and fabricated metals
- Machines
- Electronics
- Transportation equipment
Nonmanufacturing industries
Resource and resource-related industries (primary NAICS codes 11-21):
- Agriculture
- Forestry and mining
- Other extraction activities
Construction (primary NAICS codes 22 and 23) and Utilities:
- Water supply
- Sewage treatment
- Electricity generation
Service sectors (primary NAICS codes 41-93), including:
- Transportation
- Wholesale and retail trade
- Administration and finance activities
- Education and health care
- Culture and entertainment
Each country requires PRTR reporting by facilities in specific industrial sectors or undertaking specific industrial activities. PRTR reporting requirements are based in part on the industrial activity undertaken within a facility, and not only the industry code assigned to that facility.
Therefore, not all facilities within a given sector might have to report. For example, within the economic sector that includes dry-cleaning only those facilities undertaking the actual dry-cleaning process, and not clothing drop-off points, might be required to report. Another example is a food processing plant that is required to report because it has its own power plant to generate electricity.
- In Canada, all facilities that meet reporting thresholds and requirements report to the NPRI, with the exception of oil and gas exploration and certain activities such as research laboratories.
- In Mexico, all industrial sectors regulated under federal law are required to report to the RETC, along with facilities in other sectors that engage in activities subject to federal regulation. These facilities include those that use boilers, transfer hazardous wastes or release wastewater into national water bodies.
- In the United States, TRI requires reporting by federal facilities, most manufacturing facilities and industries that service manufacturing facilities (e.g., electric utilities and hazardous waste management facilities). A few resource-based sectors, including some related to oil and gas, are exempt from reporting.
North American Industry Classification System
NAICS codes were established in 2002, and since 2006 they have been incorporated into PRTR reporting to replace the individual industrial classification codes used by each country. Although there is some variation among the three countries in the subsector categorizations and codes used, the breakdown of industrial sectors into general categories is the same and is used for Taking Stock.
For more information about the system in the three countries, visit the NAICS website. Statistics Canada, the US Census Bureau, and Mexico's INEGI also provide NAICS information.
NAICS code |
Industry |
11 |
Agriculture, forestry, fishing and hunting |
21 |
Mining, quarrying and oil and gas extraction |
22 |
Electricity, water and gas distribution (utilities) |
23 |
Construction |
31/32/33 |
Manufacturing |
41/42/43 |
Wholesale trade |
44/45/46 |
Retail trade |
48/49 |
Transportation and warehousing |
51 |
Information and cultural industries |
52 |
Finance and insurance |
53 |
Real estate and rental and leasing |
54 |
Professional, scientific and technical services |
55 |
Management of companies and enterprises |
56 |
Administrative and support, waste management and remediation services |
61 |
Educational services |
62 |
Health care and social assistance |
71 |
Arts, entertainment and recreation |
72 |
Accommodation and food services |
81 |
Other services (except public administration) |
91/92/93 |
Public administration |
Both NPRI and TRI have an employee threshold, generally corresponding to the equivalent of 10 full-time employees. Recently, NPRI required that for some chemicals, such as dioxins and furans, all facilities of certain types (such as incinerators) report, regardless of the number of employees. Mexico's RETC does not have an employee threshold.
More information on reporting instructions is available on the NPRI, RETC and TRI websites:
Limitations of PRTR Data
PRTR data are valuable because :
- They reveal releases and transfers of pollutants from an individual facility, industrial sector, or geographic region.
- They can help identify trends and overall progress in reducing pollutant releases and transfers.
However, because of the PRTR reporting requirements, only a portion of all industrial pollution is being captured. Also, industrial facilities are only one of many sources of pollution in North America.
Substances released or transferred by industrial facilities have physical and chemical characteristics that influence their ultimate disposition and consequences for human and ecological health-information that PRTR data alone cannot provide. Therefore, although the data can answer some questions, you may need to consult other sources for more information.
PRTR data do not provide information on the following:
- All potentially harmful substances. The database provides information only on those pollutants reported to each country's PRTR.
- All sources of contaminants. The database includes only those facilities in the countries' industrial sectors, or undertaking specific industrial activities, that are subject to reporting to the national PRTR programs. The North American PRTRs do not include emissions from automobiles or other mobile sources, from natural sources such as forest fires or from agricultural sources. For some pollutants, these mobile, natural and agricultural sources can be large contributors to the overall amounts.
- Releases and transfers of all pollutants from a facility. Only those pollutants for which reporting thresholds are met are included.
- All facilities within required reporting sectors. In Canada and the United States, only facilities with the equivalent of 10 full-time employees must report (with certain exceptions).
- Environmental fate of or risks from the pollutants released or transferred.
- Levels of exposureof human or ecological populations to the pollutants.
- Legal limits of a pollutant from a facility.