Chatting to fellow parents about summer holiday plans at a recent school event, I was asked by a mother whether I was worried about radiation levels in Japan. Both her family and mine are travelling to Japan this summer, although neither party are travelling anywhere near Fukushima. I told her that I was actually looking forward to the clean air and getting away from Hong Kong—giving us all a rest from Hong Kong’s hideous air pollution.

She, on the other hand, told me she and her friends were worried about the potential health impact of spending a week in Japan. This is a commonly held view here, and I was reminded of something I learned about risk during my MPH course: it’s not the risk, it’s the risk perception that matters.

Recently, I was delighted to discover Safecast, a “global sensor network for collecting and sharing radiation measurements to empower people with data about their environments.” It is an excellent example of citizen science, created in the wake of the Fukushima nuclear power station accident after the 2011 Tohoku earthquake and tsunami in Japan. When the government and other authorities were clearly not going to provide the information people needed to determine the risk to their family and friends, a group of amateurs found each other through the internet and did it instead. The project then grew into probably the most comprehensive source of radiation level data in the world, as Joi Ito, director of MIT Media Lab and co-creator of Safecast, explains in this TED talk.

One of the site’s FAQs is, not surprisingly: is it safe to visit Japan? The answer might surprise some Hong Kong travellers: “Parts of Fukushima are highly contaminated, but in most of the rest of the country radiation levels are no higher, and sometimes even lower, than other major cities around the world. From our own measurements, we can say with confidence that Tokyo and Los Angeles have similar radiation readings and that the levels in Hong Kong are even higher than those in Tokyo.” This can be partly explained by higher background levels of radiation in both LA and Hong Kong compared with Tokyo before Fukushima exploded.

So, it turns out that in Hong Kong, not only do we have pollution that is causing serious and widespread illness, as well as shortening people’s lives (you can watch the death toll rising as the seconds tick away on the Hedley environmental index), but we also have radiation to contend with.

Another aspect of Hong Kongers’ distorted perception of risk is that the Daya Bay nuclear power plant, just over the border in mainland China, has been running for nearly 30 years, and scarcely gets a mention in the media or conversations about radiation risk from one year to the next. Given China’s less than stellar track record at keeping Hong Kong informed of any public health dangers emanating from across the border, we can’t assume that no news is good news. Hopefully, the citizen scientists at Safecast are continuously monitoring radiation from southern China too.

Jane Parry is a Hong Kong based public health and medical journalist and researcher.

I declare that I have read and understood the BMJ Group policy on declaration of interests and I have no relevant interests to declare.