Is the Limited Use of Marble in Japanese Homes Due to Radiation Concerns?

News

Is the Limited Use of Marble in Japanese Homes Due to Radiation Concerns?

Traditional Japanese architecture predominantly utilizes wood, and even today, most single-family homes in Japan are built with wooden structures combined with modern exterior materials. During Japan’s Meiji Restoration period over a century ago, Western architectural influences introduced materials like granite and marble, particularly in the construction of tall buildings.

The Japanese Diet Building, construction of which began in 1920, was entirely built with granite and marble. Influenced by Western architectural culture, some politicians and wealthy individuals began adopting the “granite exterior, marble interior” style in their luxurious residences.

Is the Limited Use of Marble in Japanese Homes Due to Radiation Concerns?

When did Japan gradually start abandoning the use of marble and granite in its buildings?

The shift began in the late 1950s, triggered by the Japanese government’s uranium mining investigations. Starting in 1955, the Japanese government organized geological experts to conduct uranium mining surveys across the Japanese archipelago.

The results revealed higher uranium content in marble and granite. Just a decade earlier, Japan had experienced atomic bombings in Hiroshima and Nagasaki, instilling a deep-seated fear of uranium, the key material for making atomic bombs. Consequently, a trend emerged in Japanese society to shun marble and granite.

In 2014, Japan’s Ministry of the Environment published a report titled “Unified Basic Data on the Effects of Radiation on Health,” a collaborative effort between the Ministry of the Environment and the National Institutes for Quantum and Radiological Science and Technology.

The report highlighted the presence of marble and granite deposits across Japan, with the highest concentration in the Gifu region.

Moreover, most of Gifu’s deposits are exposed at the surface, resulting in the highest natural radiation levels in the country, ranging from 0.057 to 0.110 microsieverts (uSv) per hour.

In contrast, Tokyo’s radiation levels range from 0.028 to 0.079 uSv per hour, making Gifu’s radiation levels 1.5 times higher than Tokyo’s, which is mainly situated on plains.

Using marble in homes is not inherently dangerous, but it is advisable to measure radiation levels before use.

Geologists are aware that marble and granite contain radioactive elements like uranium, thorium, and potassium-40, which emit radiation through their decay chains.

However, their radiation levels are typically relatively low, and the quantity of radioactive material can vary among different types of marble and granite.

Is the Limited Use of Marble in Japanese Homes Due to Radiation Concerns?

According to international standards, a radiation dose exceeding 100 millisieverts (mSv) per year is considered dangerous to human health.

1 millisievert (mSv) = 1000 microsieverts (uSv).

Due to the presence of some radioactive materials in natural marble and granite, Japanese people exercise caution and currently avoid using them in residential and office buildings. If used, they often opt for artificial marble and granite.

The Ministry of the Environment’s report also states that in daily life, the most significant source of radiation exposure for individuals is medical procedures and air travel.

Based on data from the United Nations and the Japan Atomic Energy Agency, the radiation exposure from a chest X-ray is 0.06 mSv, while a CT scan exposes individuals to 2.4 to 12.9 mSv. Although CT scan values may appear high, most people do not undergo them more than once a year.

Flying from Tokyo to New York and back exposes individuals to 0.11 to 0.16 mSv of radiation. Even if someone were to make this round trip 100 times in a year, they would be exposed to a maximum of 16 mSv, which is far below the 100 mSv threshold for adverse health effects.