EPUK Air Quality Significance Descriptors
Table 7.61: Definition of Impact Magnitude for Changes in Annual Mean Nitrogen Dioxide and
PM10 Concentration
Magnitude of Change
Annual Mean
Large
Increase/decrease >4µg/m3
Medium
Increase/decrease 2-4µg/m3
Small
Increase/decrease 0.4-2µg/m3
Imperceptible
Increase/decrease <0.4µg/m3
Table 7.62: Definition of Impact Magnitude for Changes in Number of Days with PM 10
3
Concentration Greater than 50μg/m
Magnitude of Change
Annual Mean
Large
Increase/decrease >4 days
Medium
Increase/decrease 2-4 days
Small
Increase/decrease 1 – 4 days
Imperceptible
Increase/decrease <1 day
Table 7.63: Air quality impact descriptors for changes to annual mean nitrogen dioxide and
PM10 concentrations at a receptor
Absolute Concentration in Relation to
Objective/Limit Value
Change in Concentration
Small
Medium
Large
Slight Adverse
Moderate
Adverse
Substantial
Adverse
Slight Adverse
Moderate
Adverse
Moderate
Adverse
Negligible
Slight Adverse
Slight Adverse
Negligible
Negligible
Slight Adverse
Slight Beneficial
Moderate
Beneficial
Substantial
Beneficial
Slight Beneficial
Moderate
Beneficial
Moderate
Beneficial
Negligible
Negligible
Slight Beneficial
Negligible
Slight Beneficial
Slight Beneficial
Increase with Scheme
Above Objective/Limit Value
3
With Scheme (>40μg/m )
Just Below Objective/Limit Value
3
With Scheme (36-40μg/m )
Below Objective/Limit Value
3
With Scheme (30-36μg/m )
Well Below Objective/Limit Value
3
With Scheme (<30μg/m )
Decrease with Scheme
Above Objective/Limit Value
3
Without Scheme (>40μg/m )
Just Below Objective/Limit Value
3
Without Scheme (36-40μg/m )
Well Below Objective/Limit Value
3
Without Scheme (<30μg/m )
Below Objective/Limit Value
3
Without Scheme (30-36μg/m )
Table 7.64: Air Quality Impact Descriptors for Changes to Number of Days with PM 10
3
Concentration Greater than 50μg/m at a Receptor
Absolute Concentration in Relation to
Objective/Limit Value
Change in Concentration
Small
Medium
Large
Slight Adverse
Moderate
Adverse
Substantial
Adverse
Slight Adverse
Moderate
Adverse
Moderate
Adverse
Negligible
Slight Adverse
Slight Adverse
Negligible
Negligible
Slight Adverse
Slight Beneficial
Moderate
Beneficial
Substantial
Beneficial
Slight Beneficial
Moderate
Beneficial
Moderate
Beneficial
Negligible
Negligible
Slight Beneficial
Negligible
Slight Beneficial
Slight Beneficial
Increase with Scheme
Above Objective/Limit Value
With Scheme (>35 days)
Just Below Objective/Limit Value
With Scheme (32 – 35 days)
Below Objective/Limit Value
With Scheme (26 - 32 days)
Well Below Objective/Limit Value
With Scheme (<26 days)
Decrease with Scheme
Above Objective/Limit Value
Without Scheme (>35 days)
Just Below Objective/Limit Value
Without Scheme (32 – 35 days)
Below Objective/Limit Value
Without Scheme (26 - 32 days)
Well Below Objective/Limit Value
Without Scheme (<26 days)