Gladiatorial games, part 27

(… continued from Gladiatorial games, part 26, posted on 3 May 2016).

In the final paragraph of part 26 I promised a report on the cross-examination of Doug Sharps, expert witness on acoustics for the HS2 Action Alliance, in respect of his views on the choice of values made for HS2 Ltd for the significant observed adverse effect level (SOAEL) thresholds to apply to HS2 operational and construction noise. It was Mr Sharps view that there should be a fixed margin of 10dB between SOAEL and the corresponding lowest observed adverse effect level (LOAEL) threshold, rather than the set of values specified by HS2 Ltd that  had margins varying between 10dB and 25dB (see footnote 1).

Both parties agreed that, in Mr Mould’s words, LOAEL and SOAEL are “evidence-based terms”, but that, in contrast to LOAEL, SOAEL is “not a concept which one finds in the World Health Organisation evidence base” – Mr Thornely-Taylor clarified that the term SOAEL was “invented by Defra”(see footnote 2). Mr Sharps also agreed with Mr Mould that there is a “relative paucity of evidence on which to place an observation-led level for SOAEL as compared to a relative quantity of evidence promulgated through the WHO in relation to NOAEL and SOAEL” and Mr Mould made the further irrefutable claim that the NPSE stops short of recommending any suitable levels for SOAEL (see footnote 3).

Despite this generally-agreed state of affairs, the Promoter did try to claim two authorities in support of his chosen SOAEL values. In the first place, Mr Mould cited the 65dB LpAeq,16hr level at which “a householder would be entitled to insulation under the prevailing noise regulations” in support of the same level being specified by HS2 Ltd as SOAEL daytime, on the basis that being entitled to an insulation grant was “a pretty good indicator that you’re likely to experience a level of impact that is at or above a significant observed adverse effect” (see footnote 4).

Whilst Mr Mould’s reasoning has a degree of soundness, the legislation governing the provision of noise insulation grants predates the adoption of the concept of SOAEL in the UK, and I can find no justification for the selection of the daytime level specified therein that would indicate that it might also be an appropriate basis for specifying the SOAEL threshold. Further the insulation grant threshold of 60dB for night is 5dB higher than the night SOAEL chosen by HS2 Ltd, so the Promoter cannot claim it to be “a pretty good indicator” in that case. For his part, Mr Sharps’ expressed the opinion that “if you align your SOAELs with legislation for noise insulation then you’re (sic) SOAELs are much too high” (see footnote 5). I think, that the jury is still out on that one.

Mr Thornely-Taylor’s only significant contribution on this subject was to point out to the Select Committee that the SOAEL for night noise “comes from the night-noise guidelines”, whilst “not using that explicit term” (see footnote 6). The only threshold of 55dB that is recommended by the World Health Organisation (WHO) in its Night Noise Guidelines for Europe is the Interim Target (IT) for Lnight,outside which is intended for countries where the full NNG (night noise guideline) limit of 40dB Lnight,outside cannot be achieved in the short term (see footnote 7). Mr Thornely-Taylor would surely be aware that, not only is this not using the “explicit term” SOAEL, but it is a very different animal to SOAEL and has, as far as I can see, no particular relevance to the choice of the night SOAEL threshold, being more akin to an interim LOAEL threshold value.

Mr Sharps’ reaction was that “you have to make a judgement on what SOAEL level you chose” and that, in his opinion, “a doubling of loudness from lowest affect to significant effect [i.e. 10dB] is a “perfectly appropriate way of establishing SOAELs”. However, he signally failed to provide any logical or evidential support for this assertion, other than a vague reference to “what the National Physical Laboratory say”, without any specific reference being cited (see footnote 8).

My verdict on the proceedings is that Mr Sharp succeeded in making the case that the spread of margins between LOAEL and SOAEL exhibited by the policy set out in E20 and E23 is unsatisfactory, but failed to make the case that the unified margin should be 10dB.

(To be concluded …)

Footnotes:

  1. The evidence presented by Mr Sharps was heard during the afternoon session of the HS2 Select Committee that was held on Monday 12thOctober 2015 (video and transcript).
  2. The term was coined for the Defra document Noise Policy Statement for England, or more correctly the Explanatory Note to this Policy, see paragraph 2.21 of that note.
  3. Mr Mould’s remarks may be found in paragraphs 113, 117, 119 and 127 of the transcript of the afternoon session of the HS2 Select Committee held on Monday 12thOctober 2015. Mr Thornely-Taylor’s clarification may be found in paragraph 258 of that transcript. The acronym NOAEL, more usually rendered NOEL, represents the no observed effect level, which is the threshold below which there is no detectable effect on health and quality of life due to the noise.
  4. Mr Mould’s quotes are taken from paragraph 170 of the transcript of the afternoon session of the HS2 Select Committee held on Monday 12thOctober 2015. The threshold for noise insulation entitlement is stated as the “specified day-time level” in clause 2(1) of the statutory instrument The Noise Insulation (Railways and Other Guided Transport Systems) Regulations 1996. The level specified therein is 68dB, but as confirmed in, for example, Clause 4(3) of those regulations, this is a façade level that is generally taken to be equivalent to a free-field value of 65dB.
  5. See paragraph 173 of the transcript of the afternoon session of the HS2 Select Committee held on Monday 12thOctober 2015.
  6. See paragraph 258 of the transcript of the afternoon session of the HS2 Select Committee held on Monday 12thOctober 2015.
  7. See Table 1 in Section 5.5 of the WHO publication Night Noise Guidelines for Europe.
  8. See paragraphs 128 and 180 of the transcript of the afternoon session of the HS2 Select Committee held on Monday 12thOctober 2015.

Acknowledgement: I wish to thank Michael Woodhouse for his suggestions and comments, which I have found invaluable in preparing this series of blogs.

Important Note: The record of the proceedings of the HS2 Select Committee from which the quotes reproduced in this blog has been taken is an uncorrected transcript of evidence, which is not yet an approved formal record. Neither witnesses nor Members have had the opportunity to correct the record in such instances, and it may therefore be subject to changes being made in the light of any such corrections being requested.

 

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