K.O.连线|夏威夷要禁止涂防晒霜了，这是为什么？

氧苯酮和桂皮酸盐是防晒霜常含有的两种化学物质，目前夏威夷正在考虑对其施以禁令。夏威夷将成为第一个禁止销售含有这两种化学物质的防晒霜的州，不过在墨西哥已有一些度假村及其他旅游景点禁止类似产品的使用。

这类化学物质能在有害紫外辐射接触皮肤前将其吸收，从而避免晒伤或者患皮肤癌。不过，最近的研究指出，氧苯酮和桂皮酸盐对珊瑚生长有极大的伤害，还会加快珊瑚的白化速率。 研究还表明这两种物质会损害珊瑚的DNA、影响其繁殖并使其受伤后更难以恢复。

这项研究导致了禁令的出台，据其推测，当这些化学物从我们身上被冲到海水中时，它们被阳光照射形成一种强氧化剂——过氧化氢。过氧化氢抑制浮游植物的生长，浮游植物虽然体积小，却是整个食物链的基础。所有以浮游植物为食的海洋生物、以这些海洋生物为食的海洋生物等等都会受影响，包括藻类，海胆，鱼类，海洋哺乳动物等。

另一项研究表明，防晒霜中的有害物质加剧珊瑚生物病毒感染，使它们更容易白化。

珊瑚的鲜艳程度是一种生物健康指标。珊瑚和一种叫做“虫黄藻”的微小藻类有共生关系：虫黄藻生活在珊瑚的骨架当中，珊瑚利用它们得到氧气、食物、和鲜艳的颜色。不过，如果生活条件不适宜（比如海水温度过高、过酸化等），那藻类就会脱离珊瑚礁。颜色不再鲜艳，也意味着食物和氧气不足。

你可能会问：“我只是涂点防晒霜，怎么就毁掉了整个生态系统呢？”皮肤上薄薄一层防晒霜看着不多，被冲到海水中可能看着不多，但在受欢迎的旅游地点，所有游客的防晒霜加在一起，每天大概有4公斤的纳米粒子冲入海洋。

那我们是否应该禁止涂防晒霜呢？国家公共广播电台的一份报导指出，氧苯酮和桂皮酸盐在40-70%的防晒霜产品中被检测到。但即使州长签署了该法规，也要在2021年才开始执行。所以，公司有充足的时间来研发出一些绿色替代品。

比如，植物可以在不合成有害化学物的情况下产生一种自然防晒霜。类菌胞素氨基酸就是这样一种由蓝藻产生的自然防晒霜，能够保护藻类不受阳光辐射损伤。在更多的可降解防晒霜上市前，我们还有一些对人体和海洋无害的矿物防晒霜（如含有氧化锌和二氧化钛的）。这些防晒霜是一种物理性（而非化学性）的防晒屏障 – 它并不会吸收紫外线，而是偏转紫外线的方向。

当然，防晒霜不是珊瑚礁面临的唯一威胁。全球变暖、过度渔捞、地表径流和农田径流的污染，和未经过处理的污水对珊瑚礁（以及整个海洋生态系统）同样是个大问题。可是，作为你我这样的普通人，不使用防晒霜起码是我们能控制的事。

作者：萨布里娜·斯蒂尔沃特（Sabrina Stierwalt）

翻译：凯瑟琳·奥尔森（Katherine Olson）

来源：《Everyday Einstein》2018年5月14日刊

Why Is Hawai’i Banning Sunscreen?

Oxybenzone and octinoxate are the chemicals found in sunscreens that are under consideration for a ban in the state of Hawai’i. While Hawai’i would be the first state to ban the sale and distribution, a few resorts and other tourist areas in Mexico already ban their use.

These ingredients offer our skin protection from burns and potentially cancer by absorbing harmful ultraviolet radiation before it reaches our skin. However, recent research shows that oxybenzone and octinoxate are detrimental to coral growth and increase the rate of coral bleaching. They are also shown to damage coral DNA, to impair coral reproduction, and to make it harder for coral to heal after breakage.

The main study that has inspired the ban against the ingredients oxybenzone and octinoxate in particular suggests that after these chemicals are washed off our bodies and into the ocean waters, they produce hydrogen peroxide when combined with sunlight. Hydrogen peroxide, in turn, acts as a strong oxidizing agent which inhibits the growth of tiny microorganisms called phytoplankton. Although tiny, phytoplankton serve as the base of the food chain affecting everything that relies on phytoplankton for food, and then everything that relies on the marine life that eats phytoplankton, and so on and so on, all the way up through algae, sea urchins, fish, and marine mammals.

Another study suggests that the harmful ingredients in sunscreens promote viral infections among coral potentially leaving them more prone to bleaching.

The vibrant colors we see in coral are an indication of the coral’s health. Coral live in a symbiotic relationship with little algae known as zooxanthellae. The zooxanthellae make the coral their home, and in exchange for that home, they provide the coral with oxygen, food, and their bright colors. But if conditions aren’t right—for example if ocean water temperatures are too high or too acidic—the algae leave the coral, stripping it of its bright color, but also its food and oxygen.

So how does my putting on a little sunscreen lead to the destruction of an entire ecosystem? It may not seem like much, for a layer of lotion to rinse off your skin and into the ocean, but an estimated 4 kilograms of nanoparticles are washed into the ocean each day at a single popular tourist spot when added up over all of the visitors.

So should we skip the sunscreen? According to a report by National Public Radio, oxybenzone and octinoxate are found in between 40 and 70% of sunscreen products. But the Hawai’i legislation, if signed by the governor, does not take effect January 1, 2021, leaving plenty of time for companies to come up with greener alternatives.

Plants, for example, produce their own natural form of sunscreen without the need for these harmful synthetic chemicals. Shinorine is one such natural sunscreen that is produced by cyanobacteria to protect themselves from solar radiation. Before more of these biodegradable sunscreens are available, there are some mineral sunscreens, like those with zinc oxide or titanium dioxide, that are still safe to use. These sunscreens act more like a physical barrier rather than a chemical one, deflecting UV rays away from your skin instead of absorbing them.

Of course, sunscreens are not the only thing threatening coral reefs. Global warming, overfishing, and pollution like runoff from storm water, agricultural runoff, and untreated sewage also pose huge problems for coral reefs and thus the entire marine ecosystem. But sunscreen usage is something that you and I as individuals can easily manage with our daily choices.