Below Objective/Limit Value With Scheme (30 - <36 µg/m3 of NO2 or Negligible Slight beneficial Slight beneficial PM10) (18.75 - <22.5 µg/m3 of PM2.5) Well Below Objective/Limit Value With Scheme (<30 µg/m3 of NO2 or PM10) Negligible Negligible Slight beneficial (<18.75 µg/m3 of PM2.5) Note 1 Where the Impact Magnitude is Imperceptible, then the Impact Description is Negligible Source: Guidelines for the Treatment of Air Quality During the Planning and Construction of National Road Schemes - National Roads Authority (2011) Table 7.4: Air Quality Impact Significance Criteria for Short Term PM10 Absolute Concentration in Change in Concentration Relation to Objective / Limit Small Medium Large Value (PM10) Increase with Scheme Above Objective/Limit Value Moderate Substantial Slight Adverse With Scheme Adverse Adverse (≥35 days) Just Below Objective/Limit Moderate Moderate Value With Scheme (32 - <35 Slight Adverse Adverse Adverse days) Below Objective/Limit Value Negligible Slight Adverse Slight Adverse With Scheme (26 - <32 days) Well Below Objective/Limit Negligible Negligible Slight Adverse Value With Scheme (<26 days) Decrease with Scheme Above Objective/Limit Value Moderate Substantial Slight Beneficial With Scheme days) Beneficial Beneficial (≥35 Just Below Objective/Limit Moderate Moderate Value With Scheme (32 - <35 Slight Beneficial Beneficial Beneficial days) Below Objective/Limit Value Slight Negligible Slight Beneficial With Scheme (26 - <32 days) Beneficial Well Below Objective/Limit Slight Negligible Negligible Value With Scheme (<26 days) Beneficial Note 1 Where the Impact Magnitude is Imperceptible, then the Impact Description is Negligible Source: Guidelines for the Treatment of Air Quality During the Planning and Construction of National Road Schemes - National Roads Authority (2011) The UK Institute of Air Quality Management (IAQM) in conjunction with the Environmental Protection UK (EPUK) has recently published impact descriptors for individual receptors based on long-term average concentrations. The matrix takes into account both the change in concentration and the resulting overall concentration as shown in Table 7.5. The guidance states that overall significance should be determined using professional judgement and consider:
Below Objective/Limit Value With Scheme (30 - <36 µg/m3 of NO2 or PM10) (18.75 - <22.5 µg/m3 of PM2.5) Negligible Slight beneficial Slight beneficial Well Below Objective/Limit Value With Scheme (<30 µg/m3 of NO2 or PM10) (<18.75 µg/m3 of PM2.5) Negligible Negligible Slight beneficial Note 1 Where the Impact Magnitude is Imperceptible, then the Impact Description is Negligible Source: Guidelines for the Treatment of Air Quality During the Planning and Construction of National Road Schemes - National Roads Authority (2011) Table 7.4: Air Quality Impact Significance Criteria for Short Term PM10 Absolute Concentration in Relation to Objective / Limit Value (PM10) Change in Concentration Small Medium Large Increase with Scheme Above Objective/Limit Value With Scheme (≥35 days) Slight Adverse Moderate Adverse Substantial Adverse Just Below Objective/Limit Value With Scheme (32 - <35 days) Slight Adverse Moderate Adverse Moderate Adverse Below Objective/Limit Value With Scheme (26 - <32 days) Negligible Slight Adverse Slight Adverse Well Below Objective/Limit Value With Scheme (<26 days) Negligible Negligible Slight Adverse Decrease with Scheme Above Objective/Limit Value With Scheme (≥35 days) Slight Beneficial Moderate Beneficial Substantial Beneficial Just Below Objective/Limit Value With Scheme (32 - <35 days) Slight Beneficial Moderate Beneficial Moderate Beneficial Below Objective/Limit Value With Scheme (26 - <32 days) Negligible Slight Beneficial Slight Beneficial Well Below Objective/Limit Value With Scheme (<26 days) Negligible Negligible Slight Beneficial Note 1 Where the Impact Magnitude is Imperceptible, then the Impact Description is Negligible Source: Guidelines for the Treatment of Air Quality During the Planning and Construction of National Road Schemes - National Roads Authority (2011) The UK Institute of Air Quality Management (IAQM) in conjunction with the Environmental Protection UK (EPUK) has recently published impact descriptors for individual receptors based on long-term average concentrations. The matrix takes into account both the change in concentration and the resulting overall concentration as shown in Table 7.5. The guidance states that overall significance should be determined using professional judgement and consider:
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