Your shower may not be getting you as clean as you think with a U.S. study finding many showerheads are dirty and may be covering you in a daily dose of bacteria that could make you sick.

    An analysis of 50 showerheads from nine U.S. cities found that about 30 percent harbored high levels of Mycobacterium avium -- a group of bacteria that can cause lung infections when inhaled or swallowed. Researchers from the University of Colorado at Boulder found the levels of Mycobacterium avium were 100 times higher than those found in typical household water.

    "If you are getting a face full of water when you first turn your shower on, that means you are probably getting a particularly high load of Mycobacterium avium, which may not be too healthy," said researcher Norman Pace in a statement.

    Mycobacterium avium is linked to pulmonary disease, causing symptoms such as a persistent drug cough, breathlessness and fatigue, and most often infects people with compromised immune system but can occasionally infect healthy people.

    Pace said research at the National Jewish Hospital in Denver found that increases in pulmonary infections in the United States in recent decades from so-called "non-tuberculosis" mycobacteria species like Mycobacterium avium may be linked to people taking more showers and fewer baths.

    He said water spurting from showerheads can distribute pathogen-filled droplets that suspend themselves in the air and can easily be inhaled into the deepest parts of the lungs.

    The problem with showerheads is that the insides provide a moist, warm, dark haven where bacteria can form sticky "biofilms" that allow them to gain a foothold and eventually set up residence in the device.

    The researchers, however, said it was still probably safe for most people to get into the shower and recommended people with compromised immune systems due to HIV or immune-suppressing drugs, use metal showerheads and change them regularly.

    "This really shouldn't concern average, healthy people. The main concern is for people who are immune-compromised," researcher Leah Feazel told Reuters Health. The findings, published in Proceedings of the National Academy of Sciences on Monday, are based on tests of about 50 showerheads taken from nine U.S. cities, including New York, Denver and Chicago.

    The researchers said showerheads are not the only potential bacterial dispersants in the home, however.

    Feazel said more research is needed to measure bacteria levels in household devices like humidifiers and evaporative coolers.

    根據美國一項研究發現：浴室噴頭非常臟，帶有致病的日劑量細菌。所以洗澡可并不是你想象的那么潔凈。

    一項對來自9個美國城市50個噴頭的研究中，30%隱藏著高含量的結核桿菌-- 一種若被人體吸入或吞食就可能引起肺部感染的菌組。美國科羅拉多州立大學的研究人員發現淋浴的結核桿菌比盆浴要高出100倍。

    "剛剛擰開噴頭你便滿臉水珠，那意味著你臉上很有可能具有高含量的結核桿菌，那很不衛生"norman陳詞到。

    結核桿菌與肺病密切相關，會引發頑固性咳嗽、呼吸急促、疲勞，大多感染免疫系統遭到破壞的人，偶爾健康的人也會被感染。

    Pace 說在丹佛猶太國立醫院的研究發現：近十幾年由類似分支桿菌屬所謂的非結核分支桿菌種類引起的美國肺病的增加與人們平時進行淋浴而不盆浴有關系。

    他說從噴頭噴出來的水把攜帶滿病原體的水滴霧化到空氣中，就很容易被吸進肺部深處。

    淋浴噴頭的問題就在：它里面提供細菌形成粘膜的潮濕、暖和、黑暗的生長環境，使得細菌在此有立腳點，最終在此長期居住。

    研究人員建議說對于大部分人來說淋浴還是安全的，但建議由HIV或服用免疫鎮壓劑導致免疫系統受損者使用金屬噴頭并要經常更換。

    "其實這并不影響正常健康的人，主要影響免疫系統受損者"Leah Feazel研究員告訴魯特健康所說。該發現發表在國家科學學會公報上的發現主要是基于對美國包括紐約、丹佛、芝加哥等9個城市50個噴頭的調查。

    但研究員們還說噴頭并不是家里唯一的細菌擴散器，Feazel 說 仍需更多對像加濕器和蒸發式冷卻器的家用設備研究來測量細菌的含量水平。