Compliance with nitrogen dioxide (NO2) annual limit value, assessment of health impacts
Case reference EIR2025/01721
Received 9 September 2025
Published 3 December 2025
Request
Please let me know:
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What steps, if any, you have taken to assess the effect on mortality and morbidity of those breaches; and
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What steps, if any, you have taken to inform the affected populations of the (i)current (2023) and (ii) expected breaches.
Please include any relevant information you have provided about the health effects of the breaches. Please provide copies of supporting documents.
Response
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What steps, if any, you have taken to assess the effect on mortality and morbidity of those breaches
None. There is no requirement as part of the assessment of limit value compliance of individual road links to complete an assessment of mortality and morbidity impacts. Therefore, we can confirm that National Highways does not hold this information, and as such this part of your request has been refused under Regulation 12(4)(a) of the Environmental Information Regulations 2004 as information not held.
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What steps, if any, you have taken to inform the affected populations of the(i) current (2023) and (ii) expected breaches. Please include any relevant information you have provided about the health effects of the breaches
National Highways has published all of their reports relating to the assessment of annual mean NO2 limit value compliance on their website, which can be accessed by anyone including members of the public in the locality of the A34.
National Highways initial assessment of limit value compliance for this section of theA34 is included in their Commission No. 1 Assessment Report and accompanying appendices. The report includes all the data used to inform their evaluation of this section of the Strategic Road Network (SRN). A copy of the report and the accompanying appendices can be viewed on the following link: https://nationalhighways.co.uk/our-work/environment/communities/air-quality/air-quality-reports/#collapse-ba548bf1-7b41-4977-be47-62d5d689acb9-7For
For information of the section of the A34 is identified by Census ID: 77436.
Additionally National Highways publishes an annual evaluation report which covers all sections of our network identified at the end of the previous calendar year, as either above the annual mean nitrogen dioxide limit value or within 10% of the limit value. The most recent annual evaluation report covers calendar year 2024 and includes the section of the SRN alongside the A34 in the Vale of White Horse. The latest results, informed by monitoring data, shows a reduction in annual mean NO2 concentrations with the A34 predicted to come into compliance in the next couple of year. A high level summary of the findings of the annual evaluation for 2024 and accompanying appendices which provide details on individual sections of the SRN can be found on the following link: https://nationalhighways.co.uk/our-work/environment/communities/air-quality/air-quality-reports/#collapse-050403fc-33f0-474d-ae3f-6fa78949f8d3-0.No
No additional information on the potential health impacts of concentrations of NO2above the limit value have been included in the various reports. To note the air quality thresholds set for the limit values are health based."
As National Highways only operates the A34 from the roads listed in your request we can confirm that National Highways does not hold the requested information for the other roads, and as such information for the other roads has been refused under Regulation 12(4)(a) of the Environmental Information Regulations 2004 as information not held.
Documents
This is National Highways' response to a freedom of information (FOI) or environmental information regulations (EIR) request.
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