Skip to main content

Reported association of air pollution and suicide rate could be confounded


A statistical association between ambient air pollution and suicide mortality has been recently reported in Environmental Health, which seems not to be scientifically supported by their data.

In this article, very low (unrealistic) suicide rate is reported, which is subjected to selection bias. Their justification is also flawed as high exposure to ambient air pollution in rural areas is lower as compared to urban residents. Weekends, holidays, time of death … are also both air pollution and suicide rate related. Reported statistical association of air pollution and suicide in this study is heavily confound.

Please see article under discussion:

Dear Editor,

I have read with interest your recent publication on association between ambient air pollution and suicide mortality [1]. Their conclusion does not seem to be epidemiologically supported.

The total rate of suicide in East Asian countries such as Japan and South Korea is relatively higher (19 × 10−5 and 17 × 10−5) than the rest of the world [2]. China, however, reports lower rates.

According to the Bulletin of the World Health Organization, suicide in China accounts for about a quarter of all suicides worldwide in the past decades [3]. High rates have also been reported in the recent years including 14.7 to 9.1 × 10−5 2006-2012 [4], 46 × 10−5 [5], and 34.5 × 10−5 (elderly suicide rate) in this country [6].

Authors reported a total of 1 550 registered suicide deaths in Guangzhou with a population of 7.7 million permanent residents (i.e. 60.8% of population of Guangzhou) between 2003 and 2012 [1]. Taking these values, the suicide rate would be 2.2 × 10−5, which is far lower than the lowest reported rates and subjected to underreporting. The extent of which seems to be large enough to reasonably question their findings.

The rate of suicide underreporting for different sexes, age groups, sexuality tendencies and types of suicide are diverse [710], which authors superficially mentioned. In addition to subpopulations, there are systematic reasons for underreporting including low accuracy in determining the underlying causes of deaths [11], inaccurate collection and coding (misclassifying of suicides as injuries) that are problematic for data stakeholders [12], stigma [13] and high standards of proof [12]. Majority of these reasons, for example, are different for urban population with high exposure to ambient air pollution and rural residents in which air pollution is low. As a result under reporting in this study is subjected to selection bias. Weekends, holidays, time of death … are also both air pollution and suicide rate related, and confound their findings to a further extent.

Reported association between air pollution and suicide is at best questionable. Findings should be treated with caution.


  1. Lin GZ, et al. The impact of ambient air pollution on suicide mortality: a case-crossover study in Guangzhou, China. Environ Health. 2016;15(1):90.

    Article  Google Scholar 

  2. Jeon SY, Reither EN, Masters RK. A population-based analysis of increasing rates of suicide mortality in Japan and South Korea, 1985-2010. BMC Public Health. 2016;16:356.

    Article  Google Scholar 

  3. Bulletin of the World Health Organization. Women and suicide in rural China. Accessed 20 Oct 2016.

  4. Liu S, et al. Spatiotemporal variation and social determinants of suicide in China, 2006-2012: findings from a nationally representative mortality surveillance system. Psychol Med. 2015;45(15):3259–68.

    Article  CAS  Google Scholar 

  5. Sun J, et al. Incidence and fatality of serious suicide attempts in a predominantly rural population in Shandong, China: a public health surveillance study. BMJ Open. 2015;5(2):e006762.

    Article  Google Scholar 

  6. Zhong BL, Chiu HF, Conwell Y. Rates and characteristics of elderly suicide in China, 2013-14. J Affect Disord. 2016;206:273–9.

    Article  Google Scholar 

  7. Speechley M, Stavraky KM. The adequacy of suicide statistics for use in epidemiology and public health. Can J Public Health. 1991;82(1):38–42.

    CAS  Google Scholar 

  8. Alves MA, Cadete MM. Suicide attempts among children and adolescents: partial or total injury? Cien Saude Colet. 2015;20(1):75–84.

    Article  Google Scholar 

  9. Deuter K, et al. Suicide in older people: revisioning new approaches. Int J Ment Health Nurs. 2016;25(2):144–50.

    Article  Google Scholar 

  10. Hottes TS, et al. Lifetime prevalence of suicide attempts among sexual minority adults by study sampling strategies: a systematic review and meta-analysis. Am J Public Health. 2016;106(5):e1–12.

    Article  Google Scholar 

  11. Sun J, et al. Suicide rates in Shandong, China, 1991-2010: rapid decrease in rural rates and steady increase in male-female ratio. J Affect Disord. 2013;146(3):361–8.

    Article  Google Scholar 

  12. De Leo D, et al. Achieving standardised reporting of suicide in Australia: rationale and program for change. Med J Aust. 2010;192(8):452–6.

    Google Scholar 

  13. Auger N, et al. Suicide in Canada: impact of injuries with undetermined intent on regional rankings. Inj Prev. 2016;22(1):76–8.

    Article  Google Scholar 

Download references



Availability of data and material

Data sharing not applicable to this article as no datasets were “generated” during the current study. However, all analysed data and material reported in this letter to editor are available. Original data that are being argued against are already published in an article in Environmental Health “Lin, G.Z., et al., The impact of ambient air pollution on suicide mortality: a case-crossover study in Guangzhou, China. Environ Health, 2016. 15(1): p. 90”.

Authors’ contributions

RA wrote the first draft of the manuscript. He did not receive an honorarium, grant, or other form of payment to produce the manuscript.

Competing interests

The author declares that he has no competing interests.

Consent for publication

N/A. In a personal level, I give my consent for publication of this letter.

Author information

Authors and Affiliations


Corresponding author

Correspondence to R. Afshari.

Rights and permissions

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Afshari, R. Reported association of air pollution and suicide rate could be confounded. Environ Health 16, 16 (2017).

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: