Reader John Davies wrote in to askST: "Is it safe to travel to Japan after the Fukushima incident, especially for women trying to get pregnant?"
Travel Correspondent Lydia Vasko answered the question.
The short answer is "yes".
It has been six years since the massive 9.0 magnitude Tohoku earthquake and subsequent tsunami hit Japan's north-eastern coast on March 11, 2011.
The event triggered a series of equipment failures and nuclear meltdowns at Fukushima No. 1power plant in what has become the world's worst nuclear disaster.
For fear of radiation poisoning, more than 100,000 people have not been allowed to return to their homes inside a roughly 20km exclusion zone around the power plant.
Fukushima made headlines again in February when it was reported that a radiation level of 530 sieverts an hour had been recorded inside one of its nuclear reactors.
To put this into perspective, one dose of one sievert of radiation can cause radiation sickness and nausea; but exposure to five sieverts would kill half of those exposed to it within a month, and a person exposed to a single dose of 10 sieverts would be dead within weeks.
In this context, 530 sieverts is a very scary number. However, it is important to remember that the measurement was taken from inside the nuclear reactor, and does not reflect the levels of radiation found in the rest of Japan.
Safecast, a global data-gathering organisation, has been using citizen volunteers to collect data on radiation and air quality around Japan since the 2011 disaster, when people felt that the Japanese government was not making accurate radiation information publicly available.
Volunteers use radiation detecting devices which record location and radiation and ping the data to Safecast every few minutes. Over 50 million readings have been collected to date. Members of the public can track these at Safecast.org, where radiation maps are published, and search the maps by location to learn real-time radiation levels in their area. They can even see where the sensor is located.
Because one sievert is a very large amount, radiation exposure is usually measured in millisieverts (mSv) or microsieverts (µSv) which are one-thousandth or one-millionth of a sievert respectively.
As of Thursday afternoon, the radiation level in the Roppongi district of Tokyo was 0.083 μSv/h, or less than one millionth of a sievert per hour. In Kyoto, levels were slightly higher at 0.13 µSv/h, while in Fukushima prefecture, near the banks of Lake Inawashiro, levels were 0.111 μSv/h.
Local radiation levels in Singapore at that same time, reported the National Environment Agency, were normal at 0.1 μSv/h, or nearly the same as in Fukushima.
According to the International Atomic Energy Agency, a United Nations organisation to promote the safe, secure and peaceful use of nuclear technologies, we are exposed to around 2.4 mSv of radiation naturally every year. This could be higher, depending on one's lifestyle and where one lives.
What this means is that travellers to Japan do not have to worry about radiation poisoning. The extreme levels of radiation are currently contained within the Fukushima nuclear plant, and it is highly unlikely that exposure to less than one-millionth of sievert of radiation per hour you will receive outside of the exclusion zone will cause any harm.
The Ministry of Foreign Affairs also does not have any travel warnings or advisories for Singaporeans travelling to Japan. So feel free to start planning your next trip to what is still one of the world's most mesmerising destinations.