Back to list Gatwick Airport Northern Runway

Representation by Bernard Fisher

Date submitted
17 October 2023
Submitted by
Members of the public/businesses

Gatwick Airport Northern Runway Comments on Climate Change and Air Quality in the Environmental Statement Contents Greenhouse Gas Emissions PM2.5 Air Quality Criteria and Assessment Model Verification for NO2 Summary and Conclusions References I will discuss issues in the following order: (1) the criterion for assessing greenhouse gas emissions and whether the emissions from this project are “significant” (2) PM2.5 air quality criteria and assessment (3) health impact of air quality (4) assessment of nitrogen dioxide within the air quality assessment Greenhouse Gas Emissions (1) The criterion for judging greenhouse gas emissions is based on IEMA Guidance on climate change, discussed in Chapter 16 of the Environment Statement. The crucial point is the alignment of greenhouse gas emissions with the pathway to Net Zero. Construction of a northern runway will lead to an increase in greenhouse gas emissions from surface access. Whether the increase is justified depends on detailed planning for meeting the Net Zero Pathway (required in statutory legislation1), which does not at present exist. (Note there is a similar lack of detailed planning to meet national targets on PM2.52) (2) The environmental statement then goes on to justify the development, because the increase in the surface access emissions is a small fraction of the total UK carbon budget (Table 16.9.8). This approach is not justified. It means that any project could be judged “insignificant”, because it is a small fraction of the total carbon budget. It effectively means that any local development should be approved! Instead one needs a detailed plan regarding future greenhouse gas emissions, which might allow an increase, if this is balanced by mitigation or a decrease elsewhere produced by greater efficiency. (3) The project appears to lead to an increase of 0.1 MtCO2e in greenhouse gas emissions between 2033-37, from surface access emissions over the 5 year period. The UK carbon budget over the same period is about 1000 MtCO2e, so the increase is about 0.01% (Table 16.9.8). The increase from surface access emissions is about 20,000 tCO2e per year. The greenhouse gas emissions from aircraft are much larger, but the consequence of statutory legislation regarding the pathway to net zero is unclear to me. Flying will add between 3 to 4 MtCO2e per year. This much greater than the road related greenhouse gas emissions, but is not localised to the UK. (4) There would be a 5.555 MtCO2e increase in aviation greenhouse gas emissions because of the project, in the years 2033-37, the period of the Sixth Carbon Budget (Table 16.9.10), or an increase of 1.111 MtCO2e per year. Total aviation emissions from Gatwick are 3% of the total UK carbon budget emissions, and the increase with the project is 0.6% of the total UK carbon budget emissions in the five year budget. Thus the report accepts that the northern runway development has an adverse impact. The aviation greenhouse gas emissions are much greater than the ground transport greenhouse gas emissions, which are 20,000 tCO2e per year. Paragraph 16.9.76 in the environmental statement appears to acknowledge that aviation has an adverse impact, but appears to put responsibility on government policy, and not on individual airports? (5) In summary, the conclusion that the impact of aviation greenhouse gas emissions is “minor adverse, not significant effect” (16.9.84) is wishful thinking. At the present time, given the absence of policy direction, it is not possible to judge the significance of aviation emissions. PM2.5 Air Quality Criteria and Assessment (6) In the air quality assessment, chapter 13 of the environmental statement, the criterion that PM2.5 concentrations should meet by 2038 appears favourable to the applicant. The applicant has chosen 2038 as a year to meet a target of 12 µg/m3, when the legislation requires 10 µg/m3 by 20402 (13.5.4). Paragraph 13.5.34 attempts to justify this choice. (7) However there are two aspects of the assessment which have been neglected. The PM2.5 concentration target should include the natural PM2.5 contribution, such as sea salt. There is no mention of the natural fraction of PM2.5, equal to about 1.4 µg/m3. This would make a 12 µg/m3 PM2.5 concentration target effectively equivalent to a 10 µg/m3 PM2.5 concentration target for manmade emissions. (8) Secondly only primary PM2.5 is considered in the calculation. NOx emissions will contribute to the formation of PM2.5 in the atmosphere. This fraction of the PM2.5 should not be neglected. This invalidates the air quality calculation which should be extended to include secondary PM2.5. (9) It is also rather cheeky to claim that the calculation is conservative (paragraph 13.5.34 and again in 18.8.20) because the assumed background concentration (the air pollution coming into the area) has been frozen at the predicted 2030 levels. The background concentrations are likely to decrease, because of actions to reduce other emissions sources in the country. So action by others, say on road transport and domestic emissions, which benefits Gatwick air quality, is being used as an argument by the applicant that the applicant should be subject to a less stringent standard! (10) It looks as though using emissions from aircraft, road transport and doubling the CARE (central area recycling enclosure) facility and 2030 background PM2.5 concentrations is the basis of the air quality assessment, which is restricted to emissions in a study area defined by a 10km x 11km grid over the airport and some affected network roads. (11) The PM2.5 air quality target2 also requires a 35% reduction in exposure by 2040. This target is not mentioned in the assessment. (12) In summary, why not use 10 µg/m3 as the annual target, as the year 2038 is close to the year 2040? If the applicant was confident the adverse effect was insignificant there would be no need to weight the assessment in the applicant’s favour. (13) The standards, which air quality should meet, are discussed in chapter 18 of the environmental statement. WHO guide values are much lower than the standards set in UK legislation. The government’s target setting has ignored NO2. The NO2 standard comes from the European Directive 2008, which would be based on research conducted in years before 2008. The NO2 air quality limit value was transposed into UK legislation in 2010. It should have come into force by 2010. Hence it may be considered well out of date. The introduction of the ULEZ zone in Greater London is aimed at reducing NO2. It is surprising given the enormous effort put into the air quality assessment that an update to the NO2 air quality standard has not been considered. The highest, predicted NO2 concentrations in Table 18.8.2 are close to the European Directive NO2 limit value of 40 µg/m3 and well exceed the WHO guide value of 10 µg/m3 and interim targets (shown in Table 18.8.2 and Table 18.8.3. Both tables should be in Chapter 13.). It seems inevitable that over the planned lifetime of this project that the UK NO2 limit value of 40 µg/m3 will be lowered. (14) The incremental 0.2 µg/m3 increase in PM2.5 concentrations from the project may appear small (shown in Table 18.8.2 and Table 18.8.3). However, the study3 leading to PM2.5 target setting considered a number of different emission scenarios. It appeared difficult to bring about large changes in PM2.5 concentration when all source contributions from primary, secondary and natural sources are included. One cannot just assume that a small fraction of a baseline concentration means a small effect. The effect of any single source is nearly always likely to be small. In a somewhat similar way to assessing the significance of greenhouse gas emissions, one needs to consider the cumulative effect of multiple sources and one source should not be judged in a preferential way. (15) Consideration of population exposure and the formation of secondary PM2.5 means that the receptors in a much wider zone of influence than that shown in Figs 13.1.1 to 13.1.9 should be considered? (16) The receptors are largely confined to a region around Gatwick. The study neglects secondary PM2.5 formed from NOx. Although the incremental increase in concentrations may be very low at longer distances, further from Gatwick, one should take into account the greater population exposed at longer distances, if one is interested in the population exposure. Hence important contributions to the air quality impact have been ignored in this air quality assessment. (17) Adding the natural component in Table 18.8.2 and Table 18.8.3 would suggest that the PM2.5 target used in the report would be exceeded at more locations. Significance of air quality impact (18) In paragraph 13.10.29 and Table 13.5.3 a case is made that the air quality impact is insignificant. This is based on using present air quality standards which are much higher, and much less strict, than the standards in the recent targets for PM2.5 and the likely future limit value put on NO2. For example, applying 10 µg/m3 as the NO2 standard in instead of 40 µg/m3, implies that an increment of 0.2 µg/m3 would be a moderate impact. 0.2 of 10 is 2% so the impact appears to be “moderate” at some receptors. (19) The assessment cannot claim to be a “worst case” calculation, nor that the air quality impact is “insignificant”. Paragraph 18.8.2 effectively concedes that other measures to address road transport will provide air quality improvements and not action taken by the project. The project will not have any effect on achieving the latest WHO guide values for PM2.5 and NO2, so the assessment ignores these guide values. (20) As an aside, one might remark that the assessment contains spurious detail to justify “insignificance”. If the effect was thought to be insignificant from the start, this could be easily demonstrated by taking an upper bound from a “back of envelope” calculation (lumping all sources together, assuming a ground-level source and a “worst case receptor” location). (21) Paragraph 18.8.27 states explicitly that the baseline PM2.5 concentration will be lower than those shown in Table 18.8.6, because of the Government’s statutory commitments to Net Zero. Yet the applicant seems to think it has no role to play and the improvement will be brought about by the action of others, on solid fuel burning, road transport and industrial combustion etc. Table 18.8.6 focuses on concentrations at receptor positions and not on the overall population exposure including secondary PM2.5. As the government has a statutory requirement to meet Net Zero it should provide guidance as how to accommodate, sustainably, developments which increase greenhouse gas emissions. (22) In order to give some idea of the effect of secondary PM2.5 on the health impact and the treatment of limited receptor locations I have included here an alternative health risk calculation. The numbers may be only approximate, but they illustrate how one may understand the possible human exposure. (23) Receptors beyond the immediate Gatwick area (10km by 11 km) would be affected by the formation of secondary PM2.5. From the emissions in the air quality Chapter 13, Table 13.10.5, the airport related emissions appear to be 31 t/y for primary PM2.5 with an increase from the project of 0.6 t/y, and for NOx 2124 t/y with an increase from the project of 99.6 t/y in 2029. (23) To illustrate how a much simpler calculation based on a “back of envelope” estimate can establish the approximate magnitude of an effect, I have used the national average Unit Health Risk Impact. This is the number of attributable deaths associated with the emission of 1000 tonnes of a precursor pollutant as a national average over the UK (over long distances beyond the project’s zone of influence). The UHRIPM2.5 is the regional health impact from primary PM2.5 associated with1000 tonnes of primary PM2.5 emissions (taken to be 60 lives lost per 1000 tonnes emitted). The UHRINOx is the regional health impact from secondary PM2.5 associated with 1000t of NOx emissions (taken to be 3 lives lost per 1000 tonnes emitted). With these UHRI factors the regional health risk impact would be (60x0.6+3x99.6)/1000 = 0.336 lives in 2029 with most coming from secondary PM2.5 associated with NOx emissions. (24) This does not take account of local primary PM2.5, nor the health effect of NO2. The UHRIlocPM25 for primary PM2.5 within the project’s zone of influence (a 10km x 11km zone) is taken to be 21 lives lost per 1000 tonnes of primary PM2.5 emitted. The UHRINO2 for NOx as NO2 is taken to be 12 lives lost per 1000 tonnes of NOx emitted. The additional terms are (21x0.6+12x99.6)/1000 = (13.6+1195.2)/1000 = 1.2 lives, again with most coming from NOx emissions. The total lives lost per annum amount to about 1.5 lives per year in 2029 according to this calculation. The project, in Table 18.8.7, contains an estimate of 0.066 attributable deaths per year, which is much lower than our estimate. Taking account of NOx emissions from aircraft on the ground would increase our estimate further. (25) From the emissions in the air quality chapter 13, Table 13.10.7, airport related emissions appear to be 32 t/y for primary PM2.5 with an increase from the project of 4.5 t/y, and 2306 t/y for NOx with an increase from the project of 370 t/y in 2038. Using the same UHRI factors, the regional health risk impact would be (60x4.5+3x370)/1000 = 1.38 lives with most coming from NO2. This does not take account of the local primary PM2.5 within the project’s zone of influence. nor the health effect of NO2. The UHRIlocPM25 for primary PM2.5 within the project’s zone of influence (a 10km x 11km area) is taken to be 21 lives lost per 1000 tonnes PM2.5 emitted. The UHRINO2 for NOx as NO2 is taken to be 12 lives lost per 1000 tonnes NOx emitted. The additional terms are (21x4.5 +12x370)/1000 = (94.5+3774)/1000 = 4, again with most coming from NOx emissions. (26) The total number of lives lost equals up to 5 per year in 2038 according to this calculation. Taking account of NOx emissions from aircraft on the ground would increase this estimate further. The airport related greenhouse gas emissions are estimated to be 32,000 tCO2e per year. We have estimated between 1 and 5 attributable deaths per year from air pollution associated with greenhouse gas emissions of 32,000 tCO2e per year. The number of deaths attributable to air pollution in 2038 is considerably higher than the project estimate of 0.6 lives per annum in Table 18.8.9. (27) Taking 3 lives per year as the midway value of the air quality impact, one would estimate 1 attributable death per year per 10,000 tCO2e emission in our calculation. Table 16.9.8 shows the reduction in UK CO2e emissions between 2020 and 2038. This is about 300 million CO2e per year if the Net Zero reduction pathway is followed. If we adopt the one attributable death per 10,000 tCO2e emission factor, this is equivalent to a health benefit of Net Zero of about 30,000 attributable lives per year. The airport related emissions will have contributed nothing to this improvement. They have only made it worse by possibly 3 lives per year. The significance of this adverse impact can only be judged in relation to an integrated plan to reduce the national exposure and not by judging one project in isolation. (28) Table 18.8.7 contains an error. 0.066 lives in 300,000 in 2029 is equivalent to about 0.022 lives in 100,000 for which the baseline mortality rate would be about 1000. So the change in the baseline rate is 0.000022 or 0.0022%. This is much greater than the figure 0.00000002% stated in the table. Is this another way the project is obsessed by insignificance? I would estimate the additional mortality in 2029 from air pollution exposure to be 0.3 to 1.5 lives per year in a much larger population. (29) Table 18.8.8 contains an error. 1.086 lives in 300,000 in 2032 is equivalent to about 0.35 lives in 100,000 for which the baseline mortality rate would be about 1000. So the change in the baseline rate is 0.000035 or 0.0035% rather than 0.000000026% as stated in the table. (The percentage also depends on the size of the population exposed). I would estimate the additional mortality in 2038 from air pollution exposure to be about 3 lives per year in a much larger population. Model Verification for NO2 (30) No target has been set for NO2, so the current limit is 40 µg/m3, set in a European Directive in 2008. The air quality report does not recognise the changing green agenda in a number of ways, so its analysis should be broadened to take account of recent policy recommendations. The air quality report should consider extending thoughts to what would be regarded acceptable in 2050 and beyond. In 2021 the World Health Organization proposed an annual guide value for annual average NO2 concentrations of 10 µg/m3. It is reasonable to expect that the UK limit value for NO2 will be lowered during the lifetime of this development. The expected air quality and greenhouse gas emissions could be compared with alternative schemes which would involve much less road transport and aircraft emissions. (31) The treatment of the correction to the modelled NO2 calculations seems rather unscientific. If there is a systematic under prediction then some reason should be cited, possibly incorrect traffic emissions. There is discussion in the scientific community of whether emissions based on traffic cycles or real world emissions are best. Appendix 13.6.1 states that the adjustment for poor model performance is a multiplicative factor of 1.2 to 2 and a generic factor 1.3 is adopted. As NO2, or NOx derived PM2.5 are the main contributions to attributable deaths in this calculation, it is important to get the NOx modelling right without incorporating correction factors. No results for NOx concentrations are presented in the reports, so one cannot check whether there is a problem with NOx emissions, or with the difficult step of estimating NO2 from NOx. (32) One wonders whether it is valid to apply a poor model, with such poor performance, to future years if one does not know the reasons for its deficiencies. The assessment recognises that background air pollution concentrations may change considerably. In paragraph 4.4.3 in Appendix 13.4.1 assumptions regarding future ozone concentrations are made without justification, which could affect NO2 concentrations. Summary and Conclusions (a) Without a detailed plan to meet Net Zero it is not possible to state that the increase in project emissions is not significant. The following conclusions in the environmental assessment are not supported: ANPS = Airports National Policy Statement (b) The air quality assessment neglects contributions and is incomplete. The argument that air quality is insignificant cannot be justified by the evidence presented. The following conclusion in the environmental assessment is not supported: (c) The calculated health impact from the development is an underprediction. One cannot be sure that the following conclusion applies. (d) The modelling of NO2 concentrations is subject to rather large uncertainties. One should not use a model to predict future concentrations unless the deficiencies of the approach are understood. The uncertainty is acknowledged in Appendix 13.6.1 but the reasons are unknown. One cannot just adjust a model prediction without explanation. Indeed if the applicant thinks that the air pollution effects are insignificant, the applicant should build in safety margins and apply these to obtain an upper bound on the expected effects. The general conclusion is that the aspects of the Environmental Statement dealing with climate and air quality are inadequate and do not form a sufficient basis for a decision. Bernard Fisher 17 October 2023 References 1STATUTORY INSTRUMENTS 2019 No. 1056 CLIMATE CHANGE The Climate Change Act 2008 (2050 Target Amendment) Order 2019 Made - - - - 26th June 2019 2STATUTORY INSTRUMENTS 2023 No. 96 ENVIRONMENTAL PROTECTION, ENGLAND The Environmental Targets (Fine Particulate Matter) (England) Regulations 2023 Made - - - - 30th January 2023 3Imperial College London, 2022. Analysis of abatement options to reduce PM2.5 concentrations. Defra contract report: SNAPCS project Support for National Air Pollution Control Strategies, February 2022