Evidence for a rise in methanol poisoning? Dirk Lachenmeier, Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe 5 June 2015 The authors are to be commended in providing a systematic literature study about methanol poisoning. The authors claim in the background section of the abstract and the article itself, that methanol poisoning may be on the rise. I cannot find evidence in the article or the cited references to substantiate this claim. The cited studies (i.e., Refs. 7.-10) were some case study reports, but no systematic time series reports about methanol poisoning. I do not think that there is much evidence to make such a claim (such evidence might be available from annual reports of poisoning control centres not included in the literature study). On the contrary, methanol was prohibited as denaturant for denatured alcohol in most jurisdictions, which led to a considerable decline of methanol poisoning outbreaks following consumption of unrecorded alcohol based on denatured alcohol . The results from the study itself also do not provide much evidence that methanol poisoning might be on the rise. On the one hand, the publication output on methanol outbreaks is absolutely co-linear to the publication output in general toxicology. A trend would only be significant, if controlled against the confounding factor of this general increase of publications. On the other hand, it can be speculated that most methanol poisoning outbreaks may be available in the grey literature (e.g. especially newspaper reports) but not in the peer-reviewed scientific literature, which is indexed by Scopus. Therefore, scientific literature may not be a good indicator for methanol poisoning outbreaks in any case. Finally, I want to comment on some misunderstandings about the occurrence of methanol in alcoholic beverages. The authors claim that methanol is a “secondary contaminant” (what is a primary contaminant, ethanol?) during illicit distillation processes. This claim must be rebutted. Methanol may occur as trace in any alcoholic beverage, but higher concentrations may only occur from the raw materials (not the distillation method). High methanol concentrations in alcoholic beverages (licit and illicit) are typically occurring in fruit derived spirits due to their content of pectins. Sometimes claims are made that methanol may derive from distillation using wood piping, but I have neither observed this practice in studying unrecorded alcohol production during the last decade, nor did I identify any hard evidence that would substantiate this claim. The large poisoning cases during the last decade (e.g. Czech republic or in Turkey) were all caused by addition of chemically pure methanol to alcohol (this practice may be caused due to the price differences between ethanol (taxed) and methanol (untaxed) in some jurisdictions, along with extremely high criminal intent or sometime pure stupidity when methanol is mismatched with ethanol) [for review about chemical composition of unrecorded alcohol see Ref. 2]. References  Lachenmeier, D. W., Rehm, J., & Gmel, G. (2007). Surrogate alcohol: what do we know and where do we go?. Alcoholism: Clinical and Experimental Research, 31(10), 1613-1624.  Rehm, J., Kailasapillai, S., Larsen, E., Rehm, M. X., Samokhvalov, A. V., Shield, K. D., ... & Lachenmeier, D. W. (2014). A systematic review of the epidemiology of unrecorded alcohol consumption and the chemical composition of unrecorded alcohol. Addiction, 109(6), 880-893. Competing interests No competing interests.