Skip to content


Environmental Health and Preventive Medicine

Open Access

Biomonitoring of metal exposure in children in a northern city of Japan

Environmental Health and Preventive Medicine201520:460

Received: 13 February 2015

Published: 7 April 2015

The original article was published in Environmental Health and Preventive Medicine 2014 20:416

The Letter to the Editor to this article has been published in Environmental Health and Preventive Medicine 2015 20:461


MercuryCadmiumMolybdenumInductively Couple Plasma Mass SpectrometryAtomic Absorption Spectrometry

Dear Editor

I recently read with interest the article by Ilmiawati et al. [1] published in Environ Health Prev Med on the exposure levels of mercury, cadmium, and lead in children of Asahikawa City, Hokkaido, Japan. This study raised some questions, which are listed below.
  • The authors describe their study as a “cross-sectional study”. According to the basic definition of epidemiological terminology, a cross-sectional study determines both exposure and disease outcome simultaneously for each subject [2]. However, this study investigated only exposure to metals, without any information on health effects. Therefore, this study cannot be called a cross-sectional study, but just a biomonitoring study.

  • This study was conducted only in Asahikawa City located in the inland areas of Hokkaido, an island at Japan’s northern extremity, with extremely cold weather. It is hard to understand why the authors consider the children from such a city as representative of Japan. In the first place, epidemiology is essentially a comparative discipline, requiring studying different places or different groups of people, but this study showed only data from one place, without any comparison. That makes interpretation of the obtained results very difficult. Additional investigations of children from other areas, such as Tokyo, are recommended.

  • It is a surprise that there was a child whose urinary cadmium level was as high as 4.67 μg/g cr., being almost equal to the levels in rice farmers with excessive oral exposure to cadmium [3]. This was probably because urinary cadmium levels were measured by inductively coupled plasma mass spectrometry (ICP-MS). In general, urine contains lots of molybdenum, which interferes with the measurement of cadmium by ICP-MS [4, 5]. Therefore, the urinary cadmium levels of children reported in this study would be much higher than the true values. Their remeasurement by atomic absorption spectrometry or molybdenum-adjusted ICP-MS is necessary.

Yours sincerely,

Hyogo Horiguchi


Authors’ Affiliations

Department of Hygiene, Kitasato University School of Medicine, Sagamihara, Japan


  1. Ilmiawati C, Yoshida T, Itoh T, Nakagi Y, Saijo Y, Sugioka Y, Sakamoto M, Ikegami A, Ogawa M, Kayama F. Biomonitoring of mercury, cadmium, and lead exposure in Japanese children: a cross-sectional study. Environ Health Prev Med. 2015;20:18–27.PubMedView ArticleGoogle Scholar
  2. Gordis L. Case control and other study designs. In: Epidemiology, 5th edn. Philadelphia: Elsevier; 2013: pp. 189–214.Google Scholar
  3. Horiguchi H, Oguma E, Sasaki S, Okubo H, Murakami K, Miyamoto K, Hosoi Y, Murata K, Kayama F. Age-relevant renal effects of cadmium exposure through consumption of home-harvested rice in female Japanese farmers. Environ Int. 2013;56:1–9.PubMedView ArticleGoogle Scholar
  4. Jarrett JM, Xiao G, Caldwell KL, Henahan D, Shakirova G, Jones RL. Eliminating molybdenum oxide interference in urine cadmium biomonitoring using ICP-DRC-MS. J Anal At Spectrom. 2008;23:962–7.View ArticleGoogle Scholar
  5. Kayama F. Combined exposure of arsenic and lead and its health effects among farmers exposed to cadmium through consumption of self-harvested rice. Report of Health and Labor Sciences Research. (2012). Available at:


© The Japanese Society for Hygiene 2015