Sunscreen: What science says about ingredient safety
夏日护肤：防晒霜的紫外线过滤剂是否安全

Melanoma is one of the deadliest cancers. It’s also one that – while still the least common form of skin cancer – is rising in prevalence around the world. Since the early 1990s, rates of melanoma in the UK have increased among every age group. Rates of non-melanoma have increased too. In the US alone, cases of non-melanoma skin cancers have grown by around 77% over the past two decades.

黑色素瘤是致死率最高的癌症之一。尽管这种皮肤癌并不常见，但其患病率在全世界正在上升。自20世纪90年代早期以来，英国各年龄层的黑色素瘤患病率均有所增长。非黑色素瘤皮肤癌也在上升。仅在美国，过去20年间非黑色素瘤皮肤癌病例就增长了77%左右。

Exposure to UV radiation is the main cause of the most common forms of skin cancer. And one of the most effective ways to avoid it, of course, is sunscreen.

皮肤过量暴露在紫外线中是引发皮肤癌的最主要因素。显而易见，最有效的预防方式就是使用防晒霜。

“Any conversation on sunscreen must start with acknowledging that there is robust evidence that it prevents skin cancer,” says Richard Weller, honorary consultant dermatologist at the University of Edinburgh.

英国爱丁堡大学名誉顾问皮肤科医师维勒（Richard Weller）表示，“任何关于防晒霜的讨论，前提都必须是承认有足够的证据证明防晒霜可以预防皮肤癌。”

This is why, although skin cancer is rising in some countries, it’s decreasing in others – particularly those that have raised the most awareness around the importance of using sunscreen. “Skin cancer rates are increasing among older generations – they’re carrying damage from decades earlier in their lives, because things have changed now,” says Adele Green, senior scientist of the cancer and population studies group at QIMR Berghofer Medical Research Institute in Australia. “Countries where rates are falling have had the biggest investments in communicating awareness, such as New Zealand, Denmark, the US and Australia.”

这就是为什么某些国家的皮肤癌患病率在上升的同时，其他国家，尤其是那些人们意识到使用防晒霜重要性的国家，皮肤癌患病率却在下降。澳大利亚昆士兰QIMR伯格霍夫医学研究所（QIMR Berghofer Medical Research Institute）癌症及人口研究资深科学家格林（Adele Green）表示，“皮肤癌在老年人群中发病率上升，因为他们皮肤在人生前几十年已开始晒伤，进入晚年后，晒伤的皮肤发生了癌变。在宣传皮肤癌防范意识投入最多的国家，皮肤癌发病率正在下降，其中包括新西兰、丹麦、美国和澳大利亚。”

But some researchers have raised concerns that, despite being an undeniably important tool in our fight against skin cancer, the formulation of sunscreen may need to be improved to contain safer ingredients – and, at worst, some sunscreens could be damaging our health.

但一些研究人员担心，虽然毫无疑问，防晒霜是预防皮肤癌的重要工具，但其配方可能需要进一步改善、使用更安全的成分，而且最坏的情况是，有些防晒霜可能危害健康。

Earlier this year the US Food and Drug Administration (FDA) – one of the two main global regulators of sunscreen ingredients around the world alongside the European Commission – removed 14 of the 16 chemicals found in sunscreens from its GRASE (generally accepted as safe and effective) category.

今年年初，欧盟以外的全球最大防晒霜成分监管机构美国食品药物管理局（FDA）将防晒霜里常见的16种化学物质中的14种从“公认安全有效（GRASE）”类别中移除。

So what is the reality?

那么，事实究竟如何呢？

Double filter

两种过滤紫外线的防晒剂

Two types of UV filters can be used for sunscreen. The most commonly used are known as organic filters, which absorb UV radiation and convert it into safer radiation. Inorganic UV filters like titanium dioxide and zinc oxide – which are broadly considered safe – reflect and scatter UV radiation away from the skin.

有两类紫外线过滤物质可用于防晒霜。最常用的一种被称为有机过滤防晒剂，能吸收紫外线，然后将其转化为对人体皮肤较安全的辐射。另一种是氧化钛和氧化锌等无机紫外线过滤物质，能够反射、散射紫外线，使其无法伤害皮肤，广泛认为很安全。

It’s long been established that some organic filters are absorbed through the skin and into the bloodstream. This alone doesn’t mean sunscreen is unsafe, but there is growing focus on the potential adverse effects of the most common UV filter worldwide: oxybenzone.

长期以来，人们一直认为某些有机过滤防晒剂会被皮肤吸收，然后进入血液。仅这一点并不意味着防晒霜不安全，但人们越来越关注全球最常见的紫外线过滤剂羟苯甲酮潜在的不利副作用。

“Little is known about systemic exposure for most active ingredients” in sunscreens, the FDA stated in its report, referring to the effects of large volumes of sunscreen absorbed through the skin and into the body.

美国食品药物管理局的报告提到经皮肤大量吸收进体内的防晒剂之作用时称，有关防晒液“中最活跃物质如何系统性起作用的真相，我们所知少之甚少”。

FDA scientists authored a paper focusing on four ingredients found in sunscreen into the skin, including oxybenzone, and concluded that absorption of sunscreen into the body may be more than a theoretical concern. However, the trial was very small – involving only 24 people.

美国食品药物管理局的科学家们撰写了一篇论文，对4种防晒霜中进入皮肤的化学成分进行研究，其中包括羟苯甲酮等，得出这样的结论：被人体吸收的防晒剂确实可能影响健康。但是，实验规模非常小，仅有24人参与。

Some lab and mice studies have found that some organic UV filters, including oxybenzone, as well as ingredients including parabens and phthalates, which can be found even in sunscreens that use inorganic UV filters, are suspected endocrine disrupters: chemicals that interfere with our hormones. But no research on humans has backed this up.

一些实验室对老鼠的研究发现，包括羟苯甲酮在内的某些有机紫外线过滤剂、以及用于无机紫外线过滤防晒霜中的对羟基苯甲酸酯和邻苯二甲酸盐等成分，都可能是内分泌干扰物，即会干扰动物激素的化学物质。但是目前没有针对人体的此类研究可以证明这一结论。

Laura Vandenberg, associate professor at the University of Massachusetts Amherst's School of Public Health and Health Sciences, says most endocrine disrupters affect male foetuses and embryos.

美国马塞诸塞州立大学阿默斯特公共卫生与健康科学学院（Amherst's School of Public Health and Health Science）副教授范德堡（Laura Vandenberg）表示，大多数内分泌干扰物会影响男性胎儿和胚胎。

High-level exposure to phthalates, in particular, has been found to disrupt development of male genitals. This could lead to problems later in life, such as reduced sperm count or increased risk of testicular cancer. However, this effect has only been found in very high doses.

接触高剂量的邻苯二甲酸盐，尤其会干扰男性生殖器官的发育。这可能导致以后人生的许多问题，例如精子数量下降或睾丸癌风险上升。但这一影响仅在剂量极高时发生。

These compounds aren’t just in sunscreens, either. Phthalates also can be found in various other cosmetics, including some soaps, shampoos, nail polishes and hair sprays, and parabens are in many hair care and make-up products.

这些化合物也不只是存在于防晒霜中。某些香皂、洗发水、指甲油、头发喷雾等其他美容产品也含有邻苯二甲酸盐，而许多护发和美妆产品中则含有对羟基苯甲酸酯。

Meanwhile, Vandenberg has found through her research that oxybenzone can affect the size of mice’s mammary glands. Oxybenzone also has been detected in breast milk. That means it could also be in the breast tissue, Vandenberg says, which could affect its development, function and health.

与此同时，范德堡还通过研究发现，羟苯甲酮可以影响老鼠的乳腺大小，而且在老鼠母乳中也检查到有这种化学物。范德堡表示，这意味着乳房组织内可能也含有羟苯甲酮，这会影响乳房的发育、功能和健康。

However, we should always be cautious when applying the findings of mice studies to humans, says David Leffell, professor of dermatology and surgery at Yale School of Medicine, who was not involved in the research.

但是，没有参与研究的耶鲁大学医学院皮肤科及外科教授勒费尔（David Leffell）表示，我们不应轻易地将老鼠实验的研究结果推定到人体上。

Critics also say research showing adverse effects of UV filters on rodents typically involved much higher levels of UV filters than human use.

批评者也表示，在老鼠身上做的实验显示，在这些啮齿类动物身上使用紫外线过滤物产生不利作用，其剂量远远高于人类日常的使用量。

For example, in 2011, a group of researchers writing in the journal Environmental Health Perspectives put into perspective the findings of one study from 2001. In that study, researchers observed that feeding oxybenzone to young rats caused their uteruses to grow by 23%.

例如，2011年一组研究人员在《环境健康视角》期刊中发表的文章就审视了2001年一项研究的观点。在2001年的研究中，研究人员观察到，给幼鼠喂食羟苯甲酮将导致其子宫增大23%。

The 2011 researchers calculated that to achieve the same cumulative amount of oxybenzone that was administered to the rats, the average US woman would have to apply sunscreen daily for anywhere from 34 to 277 years, depending on how many times they applied sunscreen per day.

2011年的研究人员经过计算，发现要达到与研究中老鼠同等的羟苯甲酮摄入量，美国女性平均需连续使用防晒霜34至277年，具体时长则取决于防晒霜的每天使用次数。

Even so, some research has found that organic UV filters may affect humans too. In one study from 2015, researchers studied 500 couples who were trying to conceive and found that male partners with higher concentrations of benzophenone-type UV filters had a 30% lower chance of conceiving each menstrual cycle.

即便如此，一些研究也发现，有机紫外线过滤剂可能对人类产生影响。在2015年的一项研究中，研究人员对500对正尝试怀孕的夫妇展开研究发现，使用含较高浓度的二苯甲酮型紫外线过滤剂防晒霜的男性，其伴侣每月月经周期受孕几率要低30%。

“The longer time to pregnancy may be influenced by subtle changes in semen quality,” says the study’s author Germaine Louis, professor of global and community health at George Mason University in Virginia, US.

美国弗吉尼亚乔治梅森大学（George Mason University）全球及社区健康教授、该研究的作者路易斯（Germaine Louis）说，“受孕所需时间较长可能受到精子质量的细微影响。”

While this is an important finding, the study does have limitations, Leffell notes, which Louis acknowledges in the paper. These limitations include reliance on only one urine measurement, and the possible variability of the concentration of UV filters measured, as their concentration lowers quickly when in the body.

勒费尔指出，虽然这是一项重要的发现，但该研究确实存在局限性。路易斯也在研究中承认了这一点。这些局限包括仅依赖一次尿液检测，以及由于紫外线过滤剂在体内时浓度会快速降低，这可能导致所测量的成分浓度发生变化。

While it’s reasonable to be concerned about the clinical impact of certain benzophenones, regardless of their source, Leffell adds that the study doesn’t draw any definite conclusions.

勒费尔补充说，虽然无论二苯甲酮源自何处，担心某些二苯甲酮的临床影响是合理的，但这项研究并没有得出任何确切的结论。

Vitamin D

维生素D

Aside from any one precise ingredient, there are concerns that sunscreen prevents the human body from making vitamin D, which we mostly get from Sun exposure. After all, vitamin D deficiency might be more prevalent than we think – could sunscreen use be to blame?

人们除了对防晒霜的某种确切成分表示担忧之外，还担心防晒霜会阻碍人体生成维生素D，因为这类维生素主要通过晒太阳获得。毕竟，缺乏维生素D可能比我们所认知的要更为常见。那么，使用防晒霜是罪魁祸首吗？

It shouldn’t be a major cause, says Rachel Neale, associate professor at QIMR Berghofer. “The mechanism of sunburn is different to vitamin D production, and there is a weight of evidence suggesting that applying sunscreen doesn’t seem to influence vitamin D levels much,” says Neale.

QIMR伯格霍夫医学研究所助理教授尼尔（Rachel Neale）表示，这不应该是一个主要原因，“因为导致晒伤的机制和人体晒太阳产生维生素D的机制并不相同。有大量证据显示，使用防晒霜似乎不大会影响维生素D的水平。”

“We’re very good at making vitamin D. And sunscreen isn’t like being inside a room – it screens the Sun out and still lets some through.”

尼尔说，“人体非常善于制造维生素D，而且使用防晒霜并不像是待在室内躲避阳光，只是挡住太阳，但还是会让一些光线穿过。”

A panel of 13 leading experts from around the world met in 2018 to discuss the balance of vitamin D and Sun protection and concluded that sunscreens are unlikely to affect the vitamin D status of healthy adults.

来自世界各地的13位顶级专家组成的小组曾在2018年开会，讨论维生素D和防晒霜之间的平衡，最终得出结论，防晒霜不太可能影响健康成年人的维生素D水平。

For those concerned about getting enough vitamin D, Neale still advises wearing sunscreen every day for those living in places where there’s strong sunshine all year round, like Australia. But in places where the Sun isn’t so strong, like the UK, she says it’s easy to get vitamin D from Sun exposure because sunscreen usually is only needed when you’re outdoors for an extended period of time.

对于那些担心维生素D摄入量是否充足的人，尼尔仍然建议，如果他们居住在澳大利亚等全年日照强烈的地区，还是需要每天使用防晒霜。但她表示，在日照不是那么强烈的地区，例如英国，人们可以很容易通过晒太阳获得维生素D，防晒霜通常只需要长时间在户外时才使用。

Concerns around sunscreen blocking vitamin D production also may be overstated because so few people use sunscreen correctly, according to Weller. It’s advised we apply two mg/cm2 to our skin, around six teaspoons, which is the amount used to determine a products’ Sun protection factor (SPF). Most people apply around a quarter of that, he says.

维勒表示，人们对防晒霜阻碍维生素D生成的担忧也可能是过虑了，因为很少有人能够正确地使用防晒霜。防晒霜的建议使用量是每平方厘米皮肤应为2毫克，约为6茶匙，这即是用来确认能起到防晒效果的标准剂量（SPF）。他说，大多数人大概只用了建议使用量的四分之一。

But could Sun exposure provide benefits other than vitamin D?

不过，除了帮助生产维生素D以外，晒太阳还有其他的益处吗？

It’s important to note that any argument emphasising the Sun’s health benefits, rather than risks, remains a controversial theory – and it doesn’t negate the warning that exposure increases the risk of skin cancer however we’re exposed to it.

需要注意的是，任何强调太阳有益健康、却不谈论风险的理论至今都是争议很大的理论，而且这种理论也不否认无论以何种方式暴露在太阳下，都会增加患皮肤癌的风险。

Still, one such benefit could be that UV radiation releases nitric oxide, a molecule produced in the body that dilates blood vessels and lowers blood pressure, which suggests that sunscreen may prevent these benefits, according to Weller.

维勒指出，即便如此，晒太阳其中一个益处就是吸收紫外线能帮助人体释放一氧化氮。人体内的一氧化氮可以扩张血管、降低血压，而使用防晒霜就可能形成阻碍。

“A growing body of evidence suggests [nitric oxide] is important for cardiovascular health and probably reduces cardiovascular disease, which is more important than preventing skin cancer,” he says.

“有越来越多的证据显示，（一氧化氮）对心血管健康很重要，而且可能减少心血管疾病发病率。其重要性远远高于预防皮肤癌。”他说。

Weller argues reducing the risk of cardiovascular disease is more important than reducing rates of skin cancer because, while rates of both are rising globally, heart disease kills a much larger proportion of people. Cardiovascular disease is the number one cause of death globally – 17.9 million people died from the disease in 2016, while between two and three million non-melanoma skin cancers and 132,000 melanoma skin cancers are diagnosed each year. Melanoma, the more aggressive of the two, has an estimated average survival rate of around 92%, and experts say death from non-melanoma cancers is rare.

维勒认为，降低心血管疾病风险远比降低皮肤癌风险重要，因为虽然两者的患病率在全球范围内均有增长，但心血管疾病的致死数量大得多。心血管疾病是全球排名第一的死亡原因，2016年就有1790万人因此而死亡。相比之下，每年确诊的非黑色素瘤皮肤癌和黑色素瘤皮肤癌的病例仅有200到300万。据估计，即或较为危险的黑色素瘤皮肤癌，患者平均存活率也高达约92%，而且专家表示，非黑色素瘤皮肤癌导致的死亡则非常罕见。

However, Weller acknowledges that his argument is controversial, and that the strongest body of evidence we have clearly points to sunscreen being beneficial to our health.

然而，维勒也承认自己的观点具有争议性，大家手头上最有力的证据也证明防晒霜对人们的健康有益。

Meanwhile, some argue that the confidence sunscreen gives us could be one reason why skin cancer rates are rising, particularly among older generations. Sunscreen emboldens us to spend longer in the Sun than we would otherwise, says Leffell.

与此同时，有的人认为，防晒霜给了人们信心，这可能是皮肤癌发病率上升的原因之一。这一点在老一辈人中尤甚。勒费尔说，防晒霜让人勇于在太阳下待得更久。

“Talking to patients, it seems people tend to not reapply sunscreen regularly when outdoors, which we need to do. The chemicals act as a sink for UV energy, and they’re not inexhaustible,” he says.

他说：“我们在和病人的交谈中发现，许多人在室外似乎不会定时补涂防晒霜，而这正是我们需要去做的。这些化学物质就好比紫外线能量储存池，不是用之不竭，需要不断补充。”

Animal planet

动物星球

It’s not just human health that scientists are investigating. Dozens of studies have demonstrated that UV filters pose a risk to marine life. Many of these chemicals can contaminate marine mammals, sea birds, fish and corals.

科学家们正在研究的并不仅限于人类健康。数十项研究表明，紫外线过滤剂对海洋生物造成了威胁。其中许多化学物质会污染海洋哺乳动物、海鸟、鱼类和珊瑚。

And while even inorganic filters, like titanium dioxide, can have an effect, one of the most toxic culprits is oxybenzone – one reason why some destinations, like Mexico’s ecological park Xcaret and Xel-Ha, have enforced a policy whereby visitors must trade in their sunscreen for one which is more biodegradable.

即便是氧化钛等无机过滤剂也可能产生影响，其中毒性最大的罪魁祸首之一就是羟苯甲酮，因此墨西哥生态公园Xcaret和Xel-Ha均制定了相关政策，要求游客必须将防晒霜更换成指定的可生物降解版本。

“Chemicals like oxybenzone can act as endocrine disruptors and cause sex change in fish, reduced growth or egg output,” says Cheryl Woodley, research scientist at the US National Oceanic and Atmospheric Administration.

美国国家海洋和大气管理局研究员伍德丽（Cheryl Woodley）说，“羟苯甲酮等化学物质可以干扰内分泌，进而导致鱼类性别发生改变，鱼类增长量或产卵量将降低。”

“Pollution in the environment from chemical sunscreens can result in a reduced resilience to climate change events, and even contribute to reproductively impaired organisms, including  coral and fish, that can go locally extinct in a matter of generations by inducing sterility and reproductive failure.”

“防晒化学物质造成的环境污染会降低环境对气候变化的抵御能力，甚至造成珊瑚、鱼类等生物的生殖障碍，进而造成生物不育和繁殖失败，最终导致当地生物将在几代人的时间内灭绝。”

In one study looking at coral communities in Hong Kong waters, researchers found higher levels of sunscreen when there is increased human activity on the coast. Some coral samples contained levels high enough to cause deformities and death in immature corals.

研究人员在研究香港水域内的珊瑚群时发现，海边人类活动增加时，珊瑚中防晒霜的含量就较高。部分珊瑚样本含有的防晒浓度足以导致生物畸形和死亡。

So what should someone concerned about their health, or that of the seascape, do?

那么担心珊瑚健康状况或者相应海域景观的人们应该做些什么呢？

Until there is definitive research on the potential effects of UV filters absorbed into our bodies, or alternatives that don’t contain ingredients associated with health risks, the consensus among experts is that we need to shield ourselves whenever we’re exposed to the Sun.

不过在有确切研究证明人体吸收的紫外线过滤剂可能有害于健康之前，或者我们可以找到不会有不潜在危险的替代品之前，专家们一致认为，只要我们暴露在太阳光下，就要做好防晒措施。

The healthiest way to do so – for both ourselves and for wildlife – is with clothing, finding shade and avoiding midday Sun. But for times that isn’t possible, we should both wear sunscreen and must apply it properly.

对我们和对野生动植物而言，最健康的方法就是使用衣物遮挡阳光、寻找荫蔽、及避开正午的当头日晒。但做不到这些的时候，我们就应该遵照正确的方法使用防晒霜。

For those concerned about potential effects of UV filters being absorbed into your skin or by wildlife, a sunscreen containing inorganic filters may be the better option.

对于那些担心紫外线过滤剂被人体皮肤或动植物吸收、造成潜在危险的人，较好的选择是使用含有无机过滤剂的防晒霜。

That may sound simple enough. But rising skin cancer rates suggest the message has been lost.

但听起来简单做起来难，皮肤癌发病率的上升意味着很多人只是听听而已，并没有这么做。

来源：纽约时报