Flight attendants may have a higher risk of a number of cancers, a new study finds.

　　一项新研究发现，空乘人员患癌症的风险可能比普通人高。

　　Researchers found that women and men on U.S. cabin crews have higher rates of many types of cancer, compared with the general population. This includes cancers of the breast, cervix, skin, thyroid and uterus, as well as gastrointestinal system cancers, which include colon, stomach, esophageal, liver and pancreatic cancers.

　　研究人员发现，与普通人群相比，许多种癌症在美国女性和男性机组人员身上的发病率都更高，其中包括乳腺癌、宫颈癌、皮肤癌、甲状腺癌、子宫癌以及消化系统癌症。消化系统癌症则包括结肠癌、胃癌、食道癌、肝癌和胰腺癌。

　　One possible explanation for these increased rates is that flight attendants are exposed to a lot of known and potential carcinogens, or cancer-causing agents, within their work environment, said lead study author Irina Mordukhovich, a research associate at Harvard University’s T.H. Chan School of Public Health.

　　该研究的主要作者、哈佛大学陈曾熙公共卫生学院副研究员埃琳娜?莫尔杜霍维奇说，对这种比率上升的一个可能的解释是，空乘人员在工作环境中接触了大量已知的潜在致癌物或致癌物质。

　　One of those carcinogens is cosmic ionizing radiation, which is elevated at higher altitudes, Mordukhovich told Live Science. This type of radiation is particularly damaging to DNA and is a known cause of breast cancer and nonmelanoma skin cancer, she said.

　　莫尔杜霍维奇对趣味科学网站记者说，其中一种致癌物是宇宙电离辐射，海拔越高，辐射水平越高。她说，这种辐射对DNA的损伤尤其大，是乳腺癌和非黑色素瘤皮肤癌的已知致病原因。

　　Air cabin crews receive the highest yearly dose of ionizing radiation on the job of all U.S. workers, she added.

　　她补充说，机组人员每年接受的电离辐射量是美国所有工作人员中最高的。

　　In the new study, the researchers looked at data from more than 5,300 flight attendants from different airlines who completed an online survey as part of the Harvard Flight Attendant Health Study. The analysis looked at the cancer rates in these flight attendants compared to a group of about 2,700 people who had a similar income and educational status but were not flight attendants.

　　在这项新研究中，研究人员研究了来自各家航空公司的5300余名空乘人员的数据，这些人完成了哈佛空乘人员健康研究的一项在线调查。这项调查研究了这些空乘人员的癌症发病率，并与大约2700名收入和受教育程度与空乘类似的非空乘人员进行对比。

　　The researchers found that in female flight attendants, the rates of breast cancer were about 50 percent higher than in women from the general population. In addition, melanoma rates were more than two times higher and nonmelanoma skin cancer rates were about four times higher in female flight attendants compared with women from the general population. (Nonmelanoma skin cancers include basal cell and squamous cell carcinomas.)

　　研究人员发现，女性空乘人员的乳腺癌发病率比普通人群女性高出50%左右。此外，与普通人群女性相比，女性空乘的黑色素瘤发病率要高出两倍以上，非黑色素瘤皮肤癌的发病率则高出四倍左右。(非黑色素瘤皮肤癌包括基底细胞癌和鳞状细胞癌)

　　These elevated cancer rates were observed despite indications of good-health behaviors, such as low levels of smoking and obesity, in the flight-attendant group as a whole, the study authors said.

　　研究报告的作者说，尽管有健康习惯的迹象，如低吸烟率和肥胖症，但总体而言，航班乘务员的癌症发病率却有所上升。

　　Cancer rates in male flight attendants were nearly 50 percent higher for melanoma and about 10 percent higher for nonmelanoma skin cancers compared with men from the general population group, according to the findings.

　　这项研究发现，与普通人群男性相比，男性空乘的黑色素瘤发病率要高出近50%，而非黑色素瘤皮肤癌的发病率则高出约10%。

　　The potential cancer risks for flight attendants are not limited to cosmic ionizing radiation. Cabin crew members are also regularly exposed to more UV radiation than the general population, which can make these workers more vulnerable to skin cancers, Mordukhovich said.

　　给空乘人员带来潜在致癌风险的并不仅有宇宙电离辐射。莫尔杜霍维奇说，空乘人员受到的紫外辐射通常也比普通人群高，这可能使他们更容易患皮肤癌。

　　In addition, some studies have found that circadian rhythm disruptions, such as jet lag, might be linked with an increased risk of cancer, she said. These disruptions could lead to changes in immune function and cell metabolism, which can reduce the suppression of tumors.

　　她说，此外有一些研究发现，昼夜节律紊乱(比如倒时差)可能与癌症风险增加有关。这些紊乱可能导致免疫功能和细胞代谢的改变，进而可能导致对肿瘤抑制的减少。

　　Another possible threat to the health of cabin crew members is chemical exposure, according to the study. The women and men who worked as flight attendants prior to 1988, when smoking was first banned on some U.S. flights, were routinely exposed to secondhand smoke while on board the aircraft.

　　研究显示，另一种可能对机组人员造成健康威胁的是化学污染。1988年，美国部分航班率先禁止吸烟。在1988年之前，飞机上的空乘人员经常接触到二手烟。

　　Other chemical contaminants found in the cabin may include engine leakages, pesticides and flame retardants, which contain compounds that may act as hormone disruptors and increase the risk of some cancers, Mordukhovich said.

　　莫尔杜霍维奇说，机舱内发现的其他化学污染物可能包括发动机燃油泄漏物、杀虫剂和阻燃剂，这些污染物中所含的化合物可能会扮演激素干扰物的角色并增加罹患某些癌症的风险。

　　Some limitations of the study are that researchers were not able to take into consideration individual UV exposures, such as sunbathing habits or leisure-time activities, which could influence skin cancer risk. In addition, cancer rates were self-reported by study participants, and these diagnoses were not confirmed by a check of their medical records by the researchers, according to the study.

　　这项研究的一些局限性在于，研究人员未能考虑到可能影响皮肤癌风险的个别紫外线暴露，如日光浴习惯或休闲活动。此外，研究参与者自主报告的癌症发病率，研究人员并未检查他们的医疗记录来证实这些诊断。

　　The study was published online today (June 25) in the journal Environmental Health.

　　这项研究6月25日发表在《环境健康》杂志的网站上。