This article was originally posted on Reddit (now deleted) on June 14, 2021. I’ve replaced links with archive links if necessary (and available). The 2020 edition of the manual is still the newest one today.

[Discussion] Health Care Manual for UV by the Japanese Ministry of the Environment

I’ve just learned that the Japanese Ministry of the Environment has published a Health Care Manual for UV (紫外線保健指導マニュアル or Shigaisen Hoken Shidō Manual; source for English title) since 2003, and that the latest edition was published in March 2020. You can download it as a 3.9 MB PDF here (linked from this page on the Japanese website, which lists all the pamphlets from the Environmental Health Department). There is no English version.

Disclaimer: I’m not a qualified expert in any way, and would really appreciate it if someone could correct me in the event that I’ve botched the incidence rate comparisons (or anything else)!

(This is probably going to be boring for most people, but I thought it’s relevant in understanding more about what Japanese sunscreens are targeting.)

Here are some things that are specific to Japan, with some additional information:

Sunburn/suntan

• [NOT FROM THE MANUAL] This is something anyone who speaks the language would already know, but in Japanese, both “sunburn” and “suntan” are represented by the same word (日焼け or hiyake). The word for “sunscreen” is 日焼け止め (also written as 日やけ止め) or hiyakedome, literally “sunburn/suntan-stopper.”

Average maximum UVI in Japan

• There are graphs showing the average maximum UVI for each month from 6 AM to 6 PM in Sapporo (peaking at UVI 8.6 at noon in July), Tsukuba (UVI 10.0 at noon in July), and Naha (UVI 12.3 at noon in July) on p. 7, with more comparisons between these three locations on the pages that follow (pp. 8–10).
• [NOT FROM THE MANUAL] For those of you who aren’t familiar with Japanese geography, Sapporo is in Hokkaido (the northernmost prefecture/island, kind of like the Alaska of Japan) and Naha is in Okinawa (the southernmost prefecture/islands, kind of like the Hawaii of Japan). Tsukuba is in Ibaraki, and is roughly 69 km or a little less than 43 miles from Tokyo and is around the middle of Japan in terms of latitude.
• [NOT FROM THE MANUAL] There’s information in English about the UV Index in Japan here on the Japan Meteorological Agency’s website.

Fitzpatrick skin phototypes in Japan (and the J-I–III skin types)

• Most Japanese people are Fitzpatrick skin phototypes II–IV, which the manual also describes as Japanese skin types J-I, J-II, and J-III (pp. 20–21).
• [NOT FROM THE MANUAL] According to a study performed by Taisho Pharmaceutical (who are behind the Coppertone brand in Japan) with 4,300 female sunscreen users in 2016, 26.7% were skin type I, 43.1% were type II, and 30.2% were type III (source). I previously assumed they were referring to Fitzpatrick skin phototypes I–III, but I now understand it’s types J-I–III, or Fitzpatrick skin types II–IV.
• It seems like they mostly don’t include skin color in the definitions for Fitzpatrick skin phototypes in Japan, let alone hair color or eye color, which is also the case for this manual.
• The manual’s definitions for Fitzpatrick skin phototypes are based on the same source as what’s given here: “A Fitzpatrick skin phototype (i–vi) was assigned to each patient based on their ability to tan and burn from sunlight. These phototypes were determined as follows: (i) burns easy, never tans; (ii) burns easy, tans minimally; (iii) burns sometimes, tans sometimes; (iv) burns minimally, tans well; (v) rarely burns, tans well; (vi) never burns, very dark skin.”
• The J-I–III skin types are described here as follows: “J-I (always burn and rarely tan), J-II (moderately burn and moderately tan) and J-III (never burn and always tan).” The manual basically says the same thing, except they add that the J-I skin type is very sensitive to UV rays and that the J-III skin type is not, and simply describe J-II as average.

Skin cancer in Japan

• Japan is among the countries with the lowest prevalence of skin cancer, along with Korea and Mongolia (p. 23).
• Here’s a translation of the graph on p. 23, which is based on data from the International Agency for Research on Cancer. It shows the age-adjusted incidence rates for skin cancer in the top 20 countries and East Asia as of 2018.
  Bar graph showing the prevalence of skin cancer, with the incidence rates on the x axis and the countries on the y axis. From highest to lowest in incidence rates: Australia, New Zealand, USA, Canada, Switzerland, Ireland, Netherlands, Germany, Luxembourg, Belgium, United Kingdom, France, Costa Rica, Denmark, Sweden, Norway, Cuba, Puerto Rico, Hungary, Italy, [gap in graph], South Korea, Mongolia, Japan, China, North Korea
• The incidence rate in Japan is roughly 1/100 of the incidence rate in Australia or New Zealand, and the death rate is also around 1/40–1/20 (ibid.).
• Historically the age-standardized incidence rate has been roughly 3–5 cases per 100,000 per year. The rate has increased from 2007 onward for both men and women, but with no clear correlation with UV rays (ibid.).
• [NOT FROM THE MANUAL] u/rczc brought up a very good point about how this probably explains why sunscreens are regulated as cosmetics in Japan, while they are OTC drugs in the US.
  • Skincare products are regulated as cosmetics, quasi-drugs, or drugs in Japan. There are sunscreens that are regulated as quasi-drugs in Japan, but it’s because they make other claims like skin-soothing, brightening, or so-called anti-aging, not because they’re sunscreens.

Recommended SPF/PA ratings

• Here’s a slightly loose translation of the diagram on p. 35 that shows which SPF/PA ratings are recommended for different levels of activity in Japan. It was originally published by the Japan Cosmetic Industry Association (JCIA) and is often reproduced on Japanese sources.
  Graph showing recommended SPF/PA ratings for different situations, with SPF ratings on the x axis and PA ratings on the y axis. The rectangular “areas” are probably intentionally fuzzy, so, roughly speaking: SPF 5 (?)–20 PA+ or so for incidental sun exposure (taking walks, shopping, etc.); SPF 15–35 PA++/+++ or so for casual sports and other recreational activities outdoors, etc.; SPF 30–50+ PA++/+++/++++ or so for recreational activities under harsh sunlight, water sports at resorts, etc.; SPF 50–50+ PA++++ or so for places with extremely strong UV rays, those who are photosensitive, etc. The graph is accompanied by a note saying that if you are particularly photosensitive due to photodermatosis or other diseases, you should consult your physician for guidelines that are appropriate for you.
• [NOT FROM THE MANUAL] Note that these recommendations are specific to Japan, where (as I just discussed) the incidence rate for skin cancer is very low. I’m guessing it’s probably only relevant if you’re Fitzpatrick skin type II–IV and either living in Japan or somewhere with a similar UVI range.

I also included additional information I looked up to supplement the point about skin cancer in the original post, but it seemed to be encouraging discussions about skin cancer by people who aren’t medical professionals, which I wasn’t comfortable with, so I’ve taken it out here. Note that I will not respond to any comments related to skin cancer.