1.

The Ambient Air Quality Directive ( 2 ) sets limit values for certain air pollutants and requires Member States to draw up air quality plans in the event of exceedance so that the exceedance period is kept as short as possible.

2.

In its judgment of 5 April 2017, Commission v Bulgaria (C‑488/15, EU:C:2017:267), the Court found that the limit values for particulate matter (PM10, namely, particles up to 10 μm in size) were systematically and continuously exceeded in all zones and agglomerations of Bulgaria and that the competent bodies had also failed to draw up sufficient air quality plans to put an end to that infringement.

3.

In the present proceedings, the Commission seeks a declaration that Bulgaria has not complied with the judgment. It claims that the Court should impose a lump sum and a daily penalty payment until full compliance.

4.

The case raises new questions as to the admissibility of such an action, since the Commission, in its invitation to submit observations, did not complain of an exceedance of the limit values since the abovementioned judgment. In addition, clarification is required as to the extent to which the Commission can object to the quality of Bulgaria’s air quality plans, irrespective of the allegation that limit values have been exceeded since the judgment, and as to the standards against which such an objection is to be examined in a procedure under Article 260 TFEU.

5.

Article 13(1) of the Ambient Air Quality Directive requires Member States to comply with various air quality limit values:

‘Member States shall ensure that, throughout their zones and agglomerations, levels of sulphur dioxide, PM10, lead, and carbon monoxide in ambient air do not exceed the limit values laid down in Annex XI.

In respect of nitrogen dioxide and benzene, the limit values specified in Annex XI may not be exceeded from the dates specified therein.

…’

6.

According to Annex XI to the Ambient Air Quality Directive, the 24-hour limit value of 50 μg/m3 PM10 for the protection of human health may not be exceeded more than 35 times a year. The annual limit value was set at 40 μg/m3 PM10. These air quality limit values have been applicable in Bulgaria, by virtue of Directive 99/30, ( 3 ) since that Member State’s accession to the European Union on 1 January 2007. ( 4 )

7.

Article 23(1) of the Ambient Air Quality Directive provides that where air quality limit values are exceeded in given zones or agglomerations, air quality plans must be established in order to achieve those values:

‘Where, in given zones or agglomerations, the levels of pollutants in ambient air exceed any limit value or target value, plus any relevant margin of tolerance in each case, Member States shall ensure that air quality plans are established for those zones and agglomerations in order to achieve the related limit value or target value specified in Annexes XI and XIV.

In the event of exceedances of those limit values for which the attainment deadline is already expired, the air quality plans shall set out appropriate measures, so that the exceedance period can be kept as short as possible. …

Those air quality plans shall incorporate at least the information listed in Section A of Annex XV …

…’

8.

Article 27(2) of the Ambient Air Quality Directive requires Member States to make information available to the Commission no later than nine months after the end of each year for the purpose of assessing compliance with the limit values.

9.

In its judgment of 5 April 2017, Commission v Bulgaria (C‑488/15, EU:C:2017:267), the Court held that:

Bulgaria had failed to fulfil its obligations under the provisions of Article 13(1) of, in conjunction with Annex XI to, the Ambient Air Quality Directive; and

10.

Following the judgment of 5 April 2017, Bulgaria provided information concerning its compliance with the judgment on several occasions, at the request of the Commission.

11.

Bulgaria also continued to transmit its PM10 pollution readings to the Commission. According to the information provided by the Commission at the hearing, that Member State transmitted, in particular in September 2018, the values for 2017, which, however, were subject to subsequent correction. According to the Commission, those corrections were communicated on 6 November 2018.

12.

Nevertheless, on 9 November 2018, the Commission formally invited Bulgaria to submit observations in accordance with Article 260(2) TFEU, setting it a deadline of 9 January 2019 within which to send its reply. At Bulgaria’s request, the Commission extended that deadline to 9 February 2019.

13.

In that letter of formal notice, the Commission stated that the exceedance of the limit values continued in 2015 and 2016.

14.

The Commission also complained that Bulgaria had not submitted new air quality plans for improving air quality. The Commission further stated that national measures had been announced, but almost all of them had not yet been implemented. Neither the progress of the implementation nor the timetable for further implementation had been communicated. Nor was there any information regarding the expected improvement in air quality, and the measures themselves were often unclear. Lastly, the Commission stated that (financial) resources (for implementation) were necessary with regard to various measures.

15.

In its reply, received by the Commission on 18 January 2019, Bulgaria indicated that the limit values were also exceeded in 2017, but stated that the situation was improving because the degree of exceedance was decreasing.

16.

With regard to air quality plans, Bulgaria recalled that it had submitted programmes for a total of 19 towns or cities in 2017 and 2018. Further nationwide measures were being prepared.

17.

Nevertheless, on 21 March 2021, the European Commission brought the present action and claimed that the Court should:

18.

The Republic of Bulgaria claims that the Court should dismiss the action and order the Commission to pay the costs.

19.

Poland supports the form of order sought by Bulgaria.

20.

The parties submitted written observations and – with the exception of Poland – presented oral argument at the hearing held on 21 September 2022.

21.

If the Court finds by judgment that a Member State has failed to fulfil an obligation under EU law, that State is required, pursuant to Article 260(1) TFEU, to take the measures required to comply with that judgment. Although that provision does not specify the period within which a judgment must be complied with, the importance of immediate and uniform application of EU law means that the process of compliance must be initiated at once and completed as soon as possible. ( 5 )

22.

If the Commission considers that the Member State concerned has not taken the necessary measures, it may, pursuant to Article 260(2) TFEU, bring the case before the Court after giving that State the opportunity to submit its observations. In so doing, it is to specify the amount of the lump sum or penalty payment to be paid by the Member State concerned which it considers appropriate in the circumstances.

23.

In the present case, the Commission claims that the Court should declare that Bulgaria has not fully complied with the judgment of 5 April 2017 and order it to pay a lump sum and a periodic penalty payment until it complies with the judgment in full. However, the form of order sought by the Commission does not extend to BG0003 AG Varna, which is covered by the abovementioned judgment, as Bulgaria has stated that the PM10 limit values at issue have been complied with there.

24.

In what follows, it is necessary to examine, first, the admissibility of that action, then its merits, and lastly the question as to whether, and if so in what amount, a lump sum and/or penalty payment should be imposed.

25.

Bulgaria submits that the action is inadmissible on the ground of a defective pre-litigation procedure.

26.

Under Article 260(2) TFEU, before the Commission brings a case before the Court on the ground of failure to comply with a judgment, it is required to give the Member State concerned the opportunity to submit its observations. According to Bulgaria, the regularity of that procedural step is affected by an error because the Commission complains of inadequate compliance with the judgment of 5 April 2017, namely an infringement of Article 260 TFEU, but it referred only to the exceedance of limit values in 2015 and 2016 in its invitation to submit observations.

27.

With that argument, Bulgaria relies on the fact that the Commission can invite the Member State to submit its observations under Article 258 TFEU only after an infringement of EU law. This means that the obligation in respect of which the Commission alleges failure to comply must have already arisen. ( 6 )

28.

Contrary to the submission of Bulgaria, however, that is the case here.

29.

It is established that, when Bulgaria was invited to submit its observations on 9 November 2018, it was already obliged to comply with the judgment of 5 April 2017. The Commission could therefore allege a failure to comply with that obligation in the letter of formal notice.

30.

However, Bulgaria’s argument reveals another shortcoming. Specifically, the Commission does not assert in its letter of formal notice of 9 November 2018 that, since the judgment of 5 April 2017, Bulgaria has not put an end to the exceedance of the limit values which was complained of in that judgment (see Section 1). By contrast, the letter of formal notice does indeed contain the allegation that Bulgaria has not sufficiently improved its air quality plans since the judgment (see Section 2).

31.

By its first plea in law, the Commission alleges that, since the judgment of 5 April 2017, the limit values for fine particulate matter (PM10) under Article 13 of, and Annex XI to, the Ambient Air Quality Directive have continued to be exceeded in Bulgaria, despite the fact that the judgment of 5 April 2017 had found a systematic and continuous infringement of those limit values.

32.

However, in its letter of formal notice of 9 November 2018, the Commission did not specifically allege that the limit values had been exceeded since the judgment of 5 April 2017. Rather, it confined itself to discussing the exceedances in 2015 and 2016.

33.

Those exceedances relate to a period later than that covered by the judgment of 5 April 2017. It is true that they prove that the infringement of the limit values and thus of EU law persisted. However, the exceedance of the limit values in 2015 and 2016 does not necessarily mean that Bulgaria has not complied with the judgment of 5 April 2017. This is because the obligation of compliance under Article 260(1) TFEU arises only as from the date of the judgment and relates to the period thereafter.

34.

Moreover, the nature of the infringement at issue – a systematic and continuous exceedance of the limit values – does not change the fact that the Commission was required to allege an infringement of the limit values following the judgment of 5 April 2017. It is true that the exceedance in 2015 and 2016 shows that that infringement continued after the period up to 2014, which was the subject of that judgment. However, that exceedance as such did not yet constitute a breach of the obligation to comply with the judgment.

35.

In a procedure under Article 258 TFEU, such an omission would constitute a serious procedural defect, since, in that procedure, the letter of formal notice outlines for the first time the scope of the infringement of EU law in relation to which the Commission and the Member State are in dispute, namely, the subject matter of the dispute. ( 7 ) If the Commission does not expressly identify the infringement in the letter of formal notice, the letter cannot fulfil that function.

36.

It is true that the procedure laid down in Article 260(2) TFEU is different from that laid down in Article 258, since the first judgment of the Court determines the subject matter of the dispute. ( 8 ) That determination is by its nature much more precise than the determination by the letter of formal notice under Article 258, because the judgment is based on the further clarifications resulting from the pre-litigation procedure and the court proceedings. Therefore, the need to specify the subject matter of the dispute in the letter of formal notice pursuant to Article 260(2) is not as great.

37.

On the other hand, the possible legal consequences of a procedure under Article 260(2) TFEU are significantly more serious than the legal consequences of a procedure under Article 258 because, under Article 260, the Court can impose a lump sum and a penalty payment. Therefore, legal certainty and the Member State’s rights of defence require particular care on the part of the Commission when it sets out the subject matter of the dispute.

38.

It is true that Bulgaria has acknowledged that the Commission complained of insufficient compliance with the limit values since the judgment of 5 April 2017. This is shown in particular by the fact that, in its reply, Bulgaria refers to the readings in 2017, that is to say, also to the period after the judgment at issue. Bulgaria was therefore not prevented from defending itself.

39.

However, a defect in the Commission’s letter of formal notice cannot be remedied by the Member State ex post facto. This would amount to a situation in which the Member State, rather than the Commission, determines the subject matter of the dispute.

40.

Therefore, only the Commission could have remedied its omission, by means of a supplementary letter of formal notice. It would have been relatively easy for the Commission to do so, as Bulgaria had in the meantime communicated the necessary information relating to 2017, and more than two years had once more elapsed between that reply and the bringing of the action. During that period, the Commission ought merely to have sent a supplementary letter of formal notice in order to specify the subject matter of the dispute.

41.

At the hearing, the Commission claimed that Bulgaria was late in submitting the readings for 2017. This is because they were not complete until after the corrections had been received on 6 November 2018.

42.

Bulgaria’s failure to make those corrections before the expiry of the time limit for submitting readings at the end of September 2018 is potentially to be regarded as an infringement of Article 27(2) of the Ambient Air Quality Directive. Nevertheless, at the time of the invitation to submit observations, the Commission already had the figures for 2017 and could have made them the subject of that invitation. By contrast, it did not allege in its invitation any omissions on the part of Bulgaria with regard to its communication of the values for 2017.

43.

Moreover, the Commission did not otherwise attempt to demonstrate that the limit values had been exceeded since the judgment of 5 April 2017. For example, it could have concluded from the exceedance of the limit values in 2015 and 2016 – in conjunction with the lack of sufficient air quality plans, which it alleges in its second plea in law – that the limit values would probably be exceeded in 2017 as well. It would also not seem out of the question for the Commission itself to monitor the publication of air quality data by the Member States under Article 26 of the Ambient Air Quality Directive and to draw from them conclusions regarding compliance with the limit values without waiting for the figures to be officially transmitted.

44.

Therefore, despite the Commission’s clear intentions, the letter of formal notice lacked, with regard to exceedance of the limit values, a decisive element for a pre-litigation procedure under Article 260(2) TFEU, namely the statement that, in the Commission’s view, the limit values had in fact been exceeded since the judgment of 5 April 2017.

45.

That plea in law is therefore inadmissible on the ground of a defective pre-litigation procedure.

46.

By its second plea in law, the Commission alleges that Bulgaria continued to fail to fulfil its obligation under the second subparagraph of Article 23(1) of the Ambient Air Quality Directive even after the judgment of 5 April 2017. According to the Commission, Bulgaria has failed to ensure the establishment of air quality plans which provide for appropriate measures, so that the exceedance period can be kept as short as possible.

47.

By contrast, Bulgaria claims that the Commission’s failure to allege, in its invitation to submit observations, that the limit values had been exceeded since the judgment of 5 April 2017 also renders that plea in law inadmissible.

48.

However, unlike with regard to exceedance of the limit values, the Commission expressly complained, in the second paragraph of Section 3 of the letter of formal notice of 9 November 2018, that Bulgaria had hitherto not submitted, in accordance with the second subparagraph of Article 23(1) of the Ambient Air Quality Directive, sufficient new plans showing a significant improvement in the policy for mitigating and managing PM10 air pollution. ( 9 ) The Commission introduced the following paragraph by stating that Bulgaria had so far, that is to say, in the period between the judgment of 5 April 2017 and the invitation to submit observations, presented very few new measures and had not yet implemented almost any of them. In that regard, the Commission referred in particular to the adoption of the national air quality programme and amendments to the Law on Clean Air, which had not yet taken place. ( 10 ) It relied on Bulgaria’s communications of 5 June 2017, 8 March 2018 and 27 July 2018.

49.

Accordingly, in its invitation to submit observations of 9 November 2018, the Commission unambiguously complained that the alleged failure to comply with the obligation to establish air quality plans concerns the period since the judgment of 5 April 2017.

50.

It is true that, in its letter of invitation to submit observations, the Commission relies on, inter alia, a piece of evidence of very limited suitability in order to prove that complaint, namely the exceedance of the limit values in 2015 and 2016.

51.

This is because, if the limit values were no longer exceeded after the judgment of 5 April 2017, the obligation to draw up air quality plans would have also ceased to exist. In accordance with Article 23 of the Ambient Air Quality Directive, an exceedance of the limit values is a precondition for the coming into being of the obligation to establish air quality plans in the first place.

52.

However, the exceedances in 2015 and 2016 are at best very weak indications that sufficient air quality plans were not applied after the judgment of 5 April 2017. They are not sufficient in themselves to prove the continuing existence of the obligation to draw up air quality plans under the second subparagraph of Article 23(1) of the Ambient Air Quality Directive and the failure to comply with that obligation.

53.

Nevertheless, by contrast to the question as to whether the infringement complained of has been sufficiently specified in the present case, the question as to whether the Commission relies on suitable evidence to prove the alleged infringement is not a question of admissibility, but rather a question of the merits of an action.

54.

In particular, there is no reason to require that an invitation to submit observations under Article 260(2) TFEU must already list the requisite evidence in a comprehensive and exhaustive manner. Rather, it is settled case-law on the first infringement procedure under Article 258 that the letter of formal notice, which of necessity can contain only an initial brief summary of the complaints, cannot be subject to such strict requirements of precision as those imposed at the second stage of the pre-litigation procedure, namely the reasoned opinion. ( 11 )

55.

That is all the more true in the case of the procedure under Article 260(2) TFEU. This is because the Member States, by way of the Treaty of Lisbon, abolished the requirement for a reasoned opinion in that procedure, in order to simplify it. ( 12 ) It would be incompatible with such simplification to impose more stringent requirements on the proof of an infringement to be provided in the letter of formal notice.

56.

Moreover, the production of fresh evidence by which the Commission illustrates the grounds of complaint set out in the pre-litigation procedure does not alter the subject matter of the dispute. ( 13 ) Rather, the Court has ruled in procedures under Article 258 TFEU that the subject matter of an action for a supposedly continuing infringement may extend to events which took place after the reasoned opinion, provided that they are of the same kind as the events to which the opinion referred and constitute the same conduct. ( 14 )

57.

This should apply mutatis mutandis in the context of Article 260(2) TFEU, for the simple reason that, in that procedure, the Commission is not normally required to prove the infringement only at a given point in time, namely upon expiry of the time limit in the letter of formal notice. Rather, the imposition of a periodic penalty payment requires that the Commission also prove that the infringement has persisted until the Court’s judgment. ( 15 ) However, evidence of that might not yet exist at the time of the letter of formal notice.

58.

Therefore, under Article 128 of the Rules of Procedure of the Court of Justice, the Commission and the Member State may in any event produce new evidence – in the present case, for example, evidence of the exceedance of the limit values in the years 2017 to 2020 – in the application initiating proceedings and in the defence and, where a party gives reasons for the delay in submitting such evidence, also in the reply and the rejoinder and, exceptionally, after the close of the written procedure. ( 16 ) The Commission need only ensure that evidence which it submits after the letter of formal notice does not broaden the subject matter of the dispute.

59.

However, the subject matter of the second plea in law is already apparent with sufficient precision from the letter of formal notice: the Commission alleges that, since the judgment of 5 April 2017, Bulgaria has failed to comply with the obligation under the second subparagraph of Article 23(1) of the Ambient Air Quality Directive to ensure that air quality plans are established which set out appropriate measures, so that the exceedance period can be kept as short as possible. New evidence proving the existence of that obligation or casting doubt on the quality of those plans does not broaden the subject matter of the dispute.

60.

Moreover, in its letter of formal notice, the Commission already referred to other evidence in addition to the exceedances in 2015 and 2016, namely, in particular, the information provided by Bulgaria that most of the measures notified had not yet been adopted, and the – in the Commission’s view, insufficient – scope of the measures already adopted.

61.

If that submission is correct, it could, in conjunction with the determinable trend in 2015 and 2016, prove that Bulgaria continued to be required to establish air quality plans and that the Bulgarian air quality plans did not meet the requirements of the second subparagraph of Article 23(1) of the Ambient Air Quality Directive. By contrast, uncertainty as regards the continued exceedance of the limit values should not be sufficient to rebut that submission. Otherwise, it would be practically impossible for such obligations to be enforced, because neither the Commission at the time of an invitation to submit observations nor the Court at the time of its judgment ( 17 ) has up-to-date measurements. Rather, they must always rely on values from the past. Moreover, Member States could undermine the enforcement of their obligations under Article 23 merely by stopping air quality sampling or delaying the transmission of readings where such readings are an essential prerequisite for establishing the obligation.

62.

Therefore, the Commission sufficiently set out the alleged infringement in its letter of formal notice of 9 November 2018.

63.

Consequently, the action is admissible in so far as the Commission alleges that Bulgaria continues to fail to comply with its obligations under the second subparagraph of Article 23(1) of the Ambient Air Quality Directive to ensure that air quality plans are established which set out measures, so that the exceedance period can be kept as short as possible. By contrast, the submission relating to the plea in law alleging exceedance of the limit values is inadmissible.

64.

Following the statements regarding admissibility, the subject matter of the present dispute is limited to the question as to whether Bulgaria has complied with its obligations under the second subparagraph of Article 23(1) of the Ambient Air Quality Directive since the judgment of 5 April 2017.

65.

According to that provision, where, in certain zones or agglomerations, the levels of pollutants in ambient air exceed any limit value, Member States are to ensure that air quality plans are established for those zones and agglomerations setting out appropriate measures, so that the exceedance period can be kept as short as possible.

66.

The reference date which must be used for assessing whether there has been a failure to fulfil obligations under Article 260(2) TFEU is that of the expiry of the period prescribed in the invitation to submit observations issued under that provision. ( 18 ) In the present case, that period ended on 9 February 2019 (see Section 1).

67.

When examining the imposition of a lump sum and/or a penalty payment under Article 260(2) TFEU, the situation on the date of the decision of the Court in the present proceedings is also relevant. In particular, the imposition of a penalty payment is justified only in so far as the failure to comply with the earlier judgment of the Court persists (see Section 2). ( 19 )

68.

As at 9 February 2019, Bulgaria had not yet complied with the obligation under the second subparagraph of Article 23(1) of the Ambient Air Quality Directive, as established in the judgment of 5 April 2017, to ensure the establishment of air quality plans setting out measures, so that the exceedance period can be kept as short as possible.

69.

As the Commission did not refer to any exceedances since the judgment of 5 April 2017 in its letter of formal notice, there might be reason to doubt whether the obligation under Article 23 of the Ambient Air Quality Directive continued to exist on 9 February 2019. However, irrespective of the indirect indications pointing to that obligation that were contained in the letter of formal notice, ( 20 ) it is now beyond dispute that the limit values were exceeded continuously until 2020 in all zones and agglomerations covered by the present case. ( 21 ) Therefore, as at 9 February 2019, Bulgaria was required to ensure that air quality plans that met the requirements of Article 23 of the Ambient Air Quality Directive were established.

70.

The fact that, in its letter of formal notice of 9 November 2018, the Commission relied only on the 2015 and 2016 measurements does not preclude the 2017 to 2020 measurements from being taken into account as evidence of Bulgaria’s obligation to establish air quality plans. The use of those later measurements does not serve formally to establish an infringement of the limit values under Article 13 of the Ambient Air Quality Directive, but is merely evidence of the asserted obligation under the second subparagraph of Article 23(1) in relation to the air quality plans. ( 22 )

71.

The judgments concerning infringement of the Ambient Air Quality Directive which were delivered under Article 258 TFEU confirm that it is possible to produce that type of evidence. This is because, even in the pre-litigation procedure under Article 258 TFEU, the Commission, when laying down the relevant time limit in the reasoned opinion, does not yet have readings that would prove that the limit values will still be exceeded when it expires. ( 23 ) This is because, under Article 27(2) of the Ambient Air Quality Directive, the Member States are not required to notify it of those measurements until nine months after the end of the year in question. Nevertheless, the Court has established, on the basis of figures submitted at a later stage, an exceedance as at the relevant date ( 24 ) and a failure to comply with the obligation to establish adequate air quality plans. ( 25 )

72.

As the Commission correctly states, the exceedance of the limit values until 2020 is at the same time a strong indication that the air quality plans in place on 9 February 2019 were not sufficient to keep the exceedance period as short as possible. ( 26 )

73.

However, the Court has held in settled case-law that air quality plans may be adopted only on the basis of the balance between the aim of minimising the risk of pollution and the various opposing public and private interests. Therefore, it is necessary to ascertain on the basis of a case-by-case analysis whether the air quality plans drawn up by the Member State concerned comply with the second subparagraph of Article 23(1) of the Ambient Air Quality Directive. ( 27 )

74.

While Member States have a degree of discretion in deciding which measures to adopt, those measures must, in any event, ensure that the period during which the limit values are exceeded is kept as short as possible; ( 28 ) under no circumstances may it be extended indefinitely. ( 29 )

75.

In its judgment of 5 April 2017, the Court had already found that Bulgaria had failed to comply with that obligation in respect of PM10 concentrations until 2014 inclusive. ( 30 ) This does not mean, however, that, following that judgment, Bulgaria could no longer submit a plan in order to comply with its obligations under Article 23 of the Ambient Air Quality Directive. Rather, it is in the very nature of the procedure under Article 260 TFEU that the Member State concerned can (and must) take measures which, although usually too late to prevent the infringement, at least put an end to it. Accordingly, the late transposition of a directive cannot remedy the failure to comply with the time limit, but can eliminate the cause for infringement proceedings.

76.

However, as at 9 February 2019, Bulgaria had not yet taken the necessary measures to put an end to the infringement of the second subparagraph of Article 23(1) of the Ambient Air Quality Directive established in the judgment of 5 April 2017.

77.

This is because, at that time, at least not all the necessary national measures which are part of Bulgaria’s strategy to comply with the judgment of 5 April 2017 had been adopted. Those measures consist, in particular, of national programmes to improve air quality and to replace certain heating systems, as well as regulations on the design of solid fuel stoves and on fuel quality. Since Bulgaria, in its response to the Commission’s letter of formal notice, regarded those measures as being essential for compliance with the judgment of 5 April 2017, it must be assumed that the air quality plans were incomplete without those measures.

78.

There is therefore no need for a substantive examination of those measures or the local air quality plans, nor for a discussion of the expected time frame for compliance with the limit values.

79.

It must therefore be concluded that, as at 9 February 2019, Bulgaria had failed fully to comply with the judgment of 5 April 2017 with regard to its obligation under the second subparagraph of Article 23(1) of the Ambient Air Quality Directive.

80.

The current situation must be examined in order to be able to decide on the imposition of a penalty payment. Although that matter cannot be definitively assessed because not all readings for the current year are available, the air quality plans adopted in the meantime and the latest readings contain important indications. It is true that most of those plans and readings were not the subject of the invitation to submit observations of 9 November 2018. Nevertheless, their consideration does not alter the subject matter of the dispute. ( 31 ) Rather, they constitute new evidence that shows the extent to which that subject matter has become devoid of purpose in the meantime. ( 32 )

81.

At the Court’s request, Bulgaria provided the latest figures for 2021 immediately before the hearing. As those figures are still provisional, however, they cannot be of decisive importance in the present proceedings. ( 33 ) Nevertheless, subject to their finalisation, they cannot be ignored in the assessment as to whether the infringement persists.

82.

As regards the readings, the annual limit value was already exceeded in 2020 only in the agglomeration BG0002 – Plovdiv, at a sampling point in the city of Plovdiv itself. However, according to the provisional figures for 2021, that limit value was eventually complied with.

83.

By contrast, the daily limit values in 2020 were still exceeded too frequently in all the zones and agglomerations at issue, more specifically in Sofia, Asenovgrad, Plovdiv, Vidin, Montana, Gorna Oryahovica, Pernik, Smolyan, Haskovo, Pazardzhik and Burgas. According to the provisional figures for 2021, there continued to be too many exceedances in most of those places.

84.

However, according to those figures, the daily limit values were exceeded on fewer than 35 days in 2021 in Pernik and the other municipalities of BG0006 – South-East Bulgaria, in Haskovo, Pazardzhik and Burgas (for the second time since 2019). In that respect, Bulgaria appears to have relied for the first time on the assertion that some of the exceedances established were attributable to contributions from natural sources and were therefore not to be considered as exceedances of limit values in accordance with Article 20(2) of the Ambient Air Quality Directive.

85.

It is true that it cannot be ruled out that the improvement in those zones is only temporary in nature. However, if the figures for 2021 are confirmed, it can no longer be established, at least on the basis of the information available today, that air quality plans must continue to be drawn up there.

86.

In so far as the daily limit values were still exceeded too frequently in 2021, the question arises as to whether the air quality plans adopted in the meantime nevertheless meet the requirements of the second subparagraph of Article 23(1) of the Ambient Air Quality Directive.

87.

An assessment of that question presupposes, in particular, that the plans incorporate the information listed in Section A of Annex XV to the Ambient Air Quality Directive. The information in question documents, inter alia, the origin of the pollution (points 5 and 6), an analysis of possible measures for improvement of air quality (point 6) and the measures adopted and implemented (points 7 to 9), including a timetable and an estimate of the improvement in air quality to be achieved (point 8).

88.

In particular, in the absence of an estimate of the improvement of air quality planned and of the expected time required to attain those objectives in accordance with point 8(c) of Section A of Annex XV to the Ambient Air Quality Directive, it is hardly possible to assess whether, on the basis of the plan, the period has remained as short as possible. This is because, without knowledge of the measures required for compliance with the limit values, it is also not possible to assess whether a faster implementation is reasonable. The Court has also already held that that information is of central importance. ( 34 )

89.

Therefore, the absence of that information necessarily forms part of the infringement of the second subparagraph of Article 23(1) of the Ambient Air Quality Directive which the Court found in the judgment of 5 April 2017. ( 35 )

90.

Accordingly, the Commission alleged, both in the letter of formal notice ( 36 ) and in the court proceedings, that that information was not present.

91.

However, it did not address the local air quality plans.

92.

In infringement proceedings, however, it is incumbent upon the Commission to prove the allegation that the obligation has not been fulfilled and to place before the Court the information needed for it to establish that the obligation has not been fulfilled. In so doing, the Commission may not rely on any presumption. ( 37 ) That also applies in a procedure under Article 260 TFEU. ( 38 ) For this reason alone, an allegation that the air quality plans of a Member State are incomplete requires that the Commission examine all plans of the Member State concerned in that regard, that is to say, not only the national measures but also the local plans based on them.

93.

Furthermore, as the Bulgarian Government has stated in response to a request from the Court, it is possible to consult the plans of the various municipalities on the internet. It can be seen that, prima facie, they do indeed contain the information listed in Section A of Annex XV to the Ambient Air Quality Directive. Moreover, it does not appear impossible that certain Commission services are aware of this or may have even played a role in ensuring that the plans meet those requirements, since the establishment of the plans appears to have been supported with EU funds.

94.

Therefore, the Commission did not sufficiently set out the allegation that Bulgaria’s air quality plans do not contain the information required under Section A of Annex XV to the Ambient Air Quality Directive.

95.

The Commission’s failure to address the local air quality plans also undermines its criticism of the suitability of the Bulgarian measures for bringing about compliance with the limit values. This criticism also essentially targets only the national measures.

96.

However, the extent to which those national measures comply with the judgment of 5 April 2017 can be assessed only if they are examined together with the local plans. This is because the local plans build on those measures and implement them in practice. In particular, it is only on the basis of the local plans that it is possible to assess whether the measures provided for at local level, together with the national measures, are sufficient to bring about compliance with the limit values, and, if so, the point in time by which they will be complied with. Only with that information can there be a meaningful discussion as to whether additional measures are required at the national level.

97.

Since the Commission does not deal with such local estimates, its criticism of the suitability of the national measures lacks the necessary basis.

98.

Its argument must therefore be rejected in that respect also.

99.

As the Commission does not dispute the forecasts of the local plans, it must be assumed that the plans available – as submitted by Bulgaria as a whole – allow the forecast of compliance with the limit values in the entirety of Bulgaria by 2024.

100.

Accordingly, it remains to be clarified whether, if the limit values are complied with by 2024, the exceedance period would be kept as short as possible. Since that question must be assessed in the context of compliance with the judgment of 5 April 2017, the decade of exceedance prior to that judgment is thus disregarded.

101.

However, even proceeding from 5 April 2017, the limit values pursuant to the objectives of the Bulgarian measures are still not complied with for a period of almost seven years.

102.

It is true that that period is long. However, given the Member States’ leeway in balancing the conflicting interests, ( 39 ) that circumstance is not sufficient to prove an infringement. This is shown in particular by Article 22(2) of the Ambient Air Quality Directive. Under that provision, the deadline for compliance with the limit values for PM10 could be extended from 1 January 2005 to 11 June 2011, subject to certain conditions. This was a similarly long period of additional non-compliance with the limit values, which the EU legislature accepted.

103.

Moreover, the option of the abovementioned deadline extension was granted to all Member States, irrespective of their respective starting position and economic capacity. However, it is clear that compliance with the limit values for PM10 is particularly challenging in Bulgaria due to its existing heating practices. Moreover, overcoming that challenge entails significant costs, which burden Bulgaria more than other Member States due to its economic situation.

104.

A period of almost seven years until compliance with the limit values for PM10 is therefore not manifestly excessive, at least in the case of Bulgaria.

105.

It is true that this does not rule out the possibility that the limit values could be complied with more quickly in certain cases – or perhaps even nationwide. That possibility is supported in particular by the Commission’s criticism that certain national measures, for example the solid fuel standards or their enforcement, were introduced relatively late. Bulgaria has not countered this criticism.

106.

However, although a faster introduction of those measures would most likely have improved air quality, the Commission did not demonstrate that this alone would have been sufficient to bring about compliance with the limit values sooner. Rather, a finding that the period of exceedance of the limit values has not remained ‘as short as possible’ would require a specific review relating to the respective local air quality plans. As a general rule, it would also be necessary to check the balancing of the conflicting interests, which would likewise be possible only on the basis of the local air quality plans. This is because only those plans can show why certain measures were not implemented earlier at the respective location. Since the Commission does not discuss those plans, the Court cannot therefore find that the exceedance period will be too long in certain cases or even overall.

107.

It follows that the Commission’s submissions are not sufficient to establish that, to date, Bulgaria has failed to comply with the judgment of 5 April 2017 with regard to its obligations under the second subparagraph of Article 23(1) of the Ambient Air Quality Directive.

108.

On the basis of the findings to date, there is no reason to impose a penalty payment. ( 40 ) Nor does a lump sum on account of the insufficient compliance with the judgment as at 9 February 2019 seem logical to me, as Bulgaria should instead invest the scarce resources in air quality improvement.

109.

Pursuant to Article 138(3) of the Rules of Procedure, the parties are to bear their own costs where – as is the case here – each party succeeds on some and fails on other heads.

110.

I therefore propose that the Court should: