TOXMAP calculates the "trend," or "on-site release amount change," for a given facility and chemical by comparing the total on-site release amount for the most recent year of TRI data with the average of all previous years.
Specifically, subtract the average total on-site release amount (prior years) from the most recent total on-site release amount (current year). If the value is negative, the trend is downward; if the value is positive, the trend is upward.
TOXMAP's Trends Legend (directly below Trends maps) uses the greatest increase OR decrease of on-site chemical release as both the minimum and the maximum values (left and right sides) of the legend. For this reason, the Trends Legend will always display the same value on each side of the legend bar. The bar is divided into five equal intervals.
TOXMAP ignores release values of "N/A". If no release data is provided by a facility, the EPA reports the release as "zero." In these cases, TOXMAP uses "zero" as the release value when calculating the trend.
2) What if there isn't data for the most recent year?
If there is no data for the most recent year, a trend is not calculated. Refer to the map legend for the special map icon that represents this situation ("insufficient data").
3) What if there is only data for the most recent year?
If the only available data is for the most recent year, it is treated as an increase, and the trend value is set to the total on-site release value for the most recent year.
4) What if there are multiple records for a year?
If there are multiple records for a year, the total on-site release values are added together and treated as a single value for that year.
5) What if there are changes to the TRI program that affect a trend calculation?
At this time, TOXMAP's trend calculation does not account for changes to the TRI program's release or waste management data. Therefore, an apparent increase or decrease in on-site releases may actually reflect a change in TRI chemical reporting requirements. We intend to change TOXMAP to take some or all of these reporting requirement changes into account in an upcoming version of TOXMAP.
See the EPA's Making Year-to-Year Comparisons of TRI Data (http://www.epa.gov/enviro/triexplorer/yearsum.htm) for more details.
Specifically, subtract the average total on-site release amount (prior years) from the most recent total on-site release amount (current year). If the value is negative, the trend is downward; if the value is positive, the trend is upward.
TOXMAP's Trends Legend (directly below Trends maps) uses the greatest increase OR decrease of on-site chemical release as both the minimum and the maximum values (left and right sides) of the legend. For this reason, the Trends Legend will always display the same value on each side of the legend bar. The bar is divided into five equal intervals.
HANDLING SPECIAL CASES
1) What if there isn't data for one of the intermediate years?TOXMAP ignores release values of "N/A". If no release data is provided by a facility, the EPA reports the release as "zero." In these cases, TOXMAP uses "zero" as the release value when calculating the trend.
2) What if there isn't data for the most recent year?
If there is no data for the most recent year, a trend is not calculated. Refer to the map legend for the special map icon that represents this situation ("insufficient data").
3) What if there is only data for the most recent year?
If the only available data is for the most recent year, it is treated as an increase, and the trend value is set to the total on-site release value for the most recent year.
4) What if there are multiple records for a year?
If there are multiple records for a year, the total on-site release values are added together and treated as a single value for that year.
5) What if there are changes to the TRI program that affect a trend calculation?
At this time, TOXMAP's trend calculation does not account for changes to the TRI program's release or waste management data. Therefore, an apparent increase or decrease in on-site releases may actually reflect a change in TRI chemical reporting requirements. We intend to change TOXMAP to take some or all of these reporting requirement changes into account in an upcoming version of TOXMAP.
See the EPA's Making Year-to-Year Comparisons of TRI Data (http://www.epa.gov/enviro/triexplorer/yearsum.htm) for more details.
