放了一夜的水到底還能不能喝？

Do you drink water that’s been left sitting out overnight, or even for another day? Have you noticed it tastes different?

你有喝過隔夜水，甚至是放了一天的水嗎?如果喝過，你有感覺到味道不一樣了嗎?

Tap water that has been left to sit out slowly begins to acquire an off taste. Many assume that this is because of microorganisms. Treated water's added chlorine will take care of small communities of these little guys, but at room temperature they begin to multiply rapidly and can really get the party started. Even with clean water and a clean glass; one sip introduces a host of germs to the mix, in addition to whatever the water may have picked up by ambient dust.

只要把自來水放在那里不動，就會慢慢開始產(chǎn)生異味。對此，許多人都認為這是微生物在搞鬼。雖然自來水中所添加的氯氣可以消滅這些小家伙，但在室溫下，它們開始迅速繁殖，重新聚集并于水中狂歡。即使用干凈的玻璃杯裝上干凈的水，但除了環(huán)境中遍布的灰塵以外，你一口下去也會摻入一系列細菌。

But that’s not what makes old water taste stale. For that we can thank carbon dioxide. After about 12 hours tap water starts to go flat as carbon dioxide in the air starts to mix with the water in the glass, lowering its pH and giving it an off taste. But it’s most-likely safe to drink.

不過，這并不是令水味道變壞的原因，罪魁禍首其實是二氧化碳。大約12小時后，空氣中的二氧化碳開始與玻璃杯中的水混合，降低其pH值并使其具有異味。而這時候的水，一般還是可以安全飲用。

However, back to those microorganisms. If you use a dirty glass day after day, there is more of a chance of unruly bacteria making themselves known; a risk that increases if you share the glass with another mouth as well. But assuming you use a fresh glass every few days, you likely won’t have a problem. Unless. Unless the rim of the glass has been touched by dirty fingers; and especially if those dirty fingers went unwashed after using the bathroom. With those kinds of germs left to multiply in a left-out glass of water, who needs enemies?

說完罪魁禍首，再繼續(xù)說說那些微生物。如果你日復一日地使用臟掉的玻璃杯，那么細菌必然歡聚一堂。當你與別人共用玻璃杯時，風險也會增加。但只要你每隔幾天就把玻璃杯洗得干干凈凈，基本上不會有任何問題。那么，瓶裝水呢?

As for plastic water bottles that have been left out in the sun or the car, step away from the bottle, warns Dr. Kellogg Schwab, director of the Johns Hopkins University Water Institute, if it's a reusable water bottle that may contain BPA. “A chemical called bisphenol-A, or BPA, along with other things used to manufacture plastic can leach into your water if the bottle heats up or sits in the sun,” he explains. BPA, as you likely know, is a hormone disruptor that has been tentatively linked to everything from heart disease to cancer. Schwab also adds that plastic used for commercial bottled water isn’t meant to be washed or refilled, so use only one time and recycle. Or way better, don’t buy them at all; use a refillable water bottle instead.

約翰斯·霍普金斯大學水資源研究所所長Kellogg Schwab博士警告說，如果一瓶水暴露在陽光下，或是留在過汽車中，那就遠離那瓶水。他對此解釋道：「如果塑料瓶加熱或暴露在陽光下，一種名為雙酚A或稱BPA的化學物質(zhì)以及其他用于制造塑料瓶的物質(zhì)都會浸入水中」。

你或許也知道，BPA是一種激素破壞劑，與心臟病和癌癥都有所關聯(lián)。Schwab博士還補充說，瓶裝水的塑料瓶不要清洗后重新裝水，用過一次就送去回收利用吧。當然，不買瓶裝水更好，用可重復使用的水瓶裝水為佳。

If you’re concerned about drinking water that has been stored for a long time, it can also become unsafe to drink. Zane Satterfield, an engineer scientist with the National Environmental Services Center at West Virginia University, says most experts agree that tap water has a shelf life of six months. “After that point, the chlorine dissipates to the point that bacteria and algae start to grow.” And especially if you store water in a warm and/or sunny spot, or in a container that has not been properly cleaned and sealed.

此外，長時間存放的飲用水，也會變得不安全。西弗吉尼亞大學國家環(huán)境服務中心的科學家Zane Satterfield表示，大多數(shù)專家都認為自來水的保質(zhì)期為六個月。「在那之后，氯氣已經(jīng)消散到了細菌與藻類可開始生長的程度」。

當然，要是你將自來水存放在溫暖或陽光充足的地方，或是沒有經(jīng)過適當清潔與密封的容器中，那可就更糟糕了。