Going Ahead (Part I): Itai-itai Disease Remediation Efforts [from scientific journal articles]

With relation to my previous post about Itai-itai disease, rice was the staple food for most locals in Toyama Prefecture. Rice contaminated with cadmium was a main route of entry into the people's diet. Here, I have found 2 scientific journal about cadmium re-contamination in paddy fields.

In this blog post, and the next, I will share 2 scientific journals (refer to References section for the document title) that were written by the same author, Makino, with regards to the remediation efforts of cadmium-contaminated soil. Though I use to integrate scientific journal findings in past blog posts, I would like to single these 2 blog posts out as it is highly relevant to Itai-itai disease which I discussed previously. 

In the journal articles, the author covered domestic legislations and guidelines adopted by Japan government for heavy metal soil pollution. Since the outbreak of Itai-itai disease, The Agricultural Land Soil Pollution Prevention Law was enacted in 1970. This law specifically target cadmium, arsenic and copper pollution in soils. According to the regulation, paddy fields are categorized as cadmium polluted if the unpolished rice grains cultivated contains more than 1 mg Cd/ kg. This concentration was calculated using cadmium levels in rice rather than soil because the bioavailability of cadmium in soil is affected by other variables such as water management. 

In July 2006, the Codex Alimentarius Commission of the Joint FAO/ WHO Food Standards Program suggested the maximum permissixble limit to be 0.4 mg Cd/ kg instead (Codex, 2006). A full list of cadmium safety level for other crops can be found in Table 1 below. 

Table 1: International Standard Value for Cadmium Concentration in Crops by Codex (Source: Makino, 2007)

Comparing Codex standard with crops in Japan, it is known that most food produce has cadmium concentration exceeding permissible levels (refer to Table 2 below). 

Table 2: Excess Rate of Cadmium in relevant crops based on Codex International Standards (Source, MAFF, 2002)

Amongst all crops, it is important for polished rice to meet safety compliance because 34% to 50% of cadmium intake by Japanese comes from rice (Kawada and Suzuki, 1998). Besides ingesting harmful cadmium, a range of other heavy metals is also present in this staple food (refer to Table 3 below). It can then be said that soils in Japan are not only polluted with cadmium, it contains other heavy metals that are above world average standards too. This makes Japan’s soil pollution a major environmental and health concern. 

Table 3: Heavy Metals Concentraion in Japanese Brown Rice and Soils (Source: Makino, 2007)

In a bid to address heavy metal soil pollution, the Japan government passed another law in year 2002, the Soil Contamination Countermeasures Law. This law not only regulates cadmium concentration in soils and soil leachate, it also oversees other heavy metals (refer to Table 4 below). 

Table 4: Japan Laws that regulates Heavy Metal Contamination in soils (Source: Makino, 2007)

With these two laws in place, 87.2% of total polluted land (7,327 hectare) was remedied, as of year 2005 (refer to Image 1 below). 

Image 1: Areas in Japan where soil remediation efforts has completed or is in progress (Source: MOE, 2006)

Using a soil contamination prevention protocol (refer to Image 2 below), Japan is trying its best to clean-up pollution on its land since industrialization started. To deter companies from polluting further, a polluter pay principle applies. From Image 2, we can identify that the cost burden of remedial operations are split between the State and enterprises. 

Image 2: Outline of Law on Soil Contamination Prevention in Japan Farmland (Source: MOE, 2006)

In my opinion, I think more penalties should be laid on businesses as it is the source of most pollution. In addition, there are diffuse point sources of soil pollution and this would be tough to identify. Having a sound legal system is then insufficient to stop soil pollution completely. I would suggest the government to educate small-scale farmers (whom are vulnerable to diffuse point source pollution) about effective soil remediation methods. Collectively then can the soils in Japan recover and its food crops safe for human consumption. In my next post, I will discuss the types of soil remediation methods outlined in the science article.  

References

Kawada, T., Suzuki, S., 1998. A review on the cadmium content of rice, daily cadmium intake, and accumulation in the kidneys. J. Occup. Health. 40, 264-269.

Makino, T. (2007). Heavy metal pollution of soil and a new approach to its remediation: research experiences in Japan. Food and Fertilizer Technology Center.

MakinoA, T., KamiyaB, T., SekiyaC, N., MaejimaA, Y., AkahaneA, I., & TakanoB, H. (2010, August). Chemical remediation of cadmium-contaminated paddy soils by washing with ferric chloride: Cd extraction mechanism and on-site verification. In Proceedings of the 19th World Congress of Soil Science: Soil solutions for a changing world, Brisbane, Australia, 1-6 August 2010. Symposium 3.5. 1 Heavy metal contaminated soils (pp. 35-38). International Union of Soil Sciences (IUSS), c/o Institut für Bodenforschung, Universität für Bodenkultur.

MOE, 2006. Enforcement status of Agricultural Land-Soil Pollution Prevention Law in 2005 fiscal year. MOE, Japan, Available at: http:// w w w . e n v . g o . j p / w a t e r / d o j o / n o u y o /jokyo_h17.pdf (in Japanese).

MAFF, 2002. Survey of the cadmium contained in agricultural products. MAFF, Japan, pp.1-45. Available at: http://www.maff.go.jp/ cd/PDF/C11.pdf and http://www.maff.go.jp/cd/PDF/C12.pdf