Zhang Feng, Lee Jiyoung, Liang Song, Shum C K
Environmental Science Graduate Program, The Ohio State University, Columbus, OH, USA.
College of Public Health, Division of Environmental Health Sciences, The Ohio State University, Columbus, OH, USA.
Environ Health. 2015 May 7;14:41. doi: 10.1186/s12940-015-0026-7.
Harmful cyanobacterial blooms present a global threat to human health. There is evidence suggesting that cyanobacterial toxins can cause liver damage and cancer. However, because there is little epidemiologic research on the effects of these toxins in humans, the excess risk of liver disease remains uncertain. The purpose of this study is to estimate the spatial distribution of cyanobacterial blooms in the United States and to conduct a Bayesian statistical analysis to test the hypothesis that contamination from cyanobacterial blooms is a potential risk factor for non-alcoholic liver disease.
An ecological study design was employed, in which county-specific gender and age standardized mortality rates (SMR) of non-alcoholic liver disease in the United States were computed between 1999 and 2010. Bloom coverage maps were produced based on estimated phycocyanin levels from MERIS (Medium Resolution Imaging Spectrometer) water color imageries from 08/01/2005 to 09/30/2005. A scan statistical tool was used to identify significant clusters of death from non-alcoholic liver disease. A map of local indicator of spatial association (LISA) clusters and a Bayesian spatial regression model were used to analyze the relationship between cyanobacterial bloom coverage and death from non-alcoholic liver disease.
Cyanobacterial blooms were found to be widely spread in the United States, including coastal areas; 62% of the counties (1949 out of 3109) showed signs of cyanobacterial blooms measured with MERIS. Significant clusters of deaths attributable to non-alcoholic liver disease were identified in the coastal areas impacted by cyanobacterial blooms. Bayesian regression analysis showed that bloom coverage was significantly related to the risk of non-alcoholic liver disease death. The risk from non-alcoholic liver disease increased by 0.3% (95% CI, 0.1% to 0.5%) with each 1% increase in bloom coverage in the affected county after adjusting for age, gender, educational level, and race.
At the population level, there is a statistically significant association between cyanobacterial blooms and non-alcoholic liver disease in the contiguous United States. Remote sensing-based water monitoring provides a useful tool for assessing health hazards, but additional studies are needed to establish a specific association between cyanobacterial blooms and liver disease.
有害蓝藻水华对人类健康构成全球威胁。有证据表明蓝藻毒素可导致肝损伤和癌症。然而，由于关于这些毒素对人类影响的流行病学研究较少，肝病的额外风险仍不确定。本研究的目的是估计美国蓝藻水华的空间分布，并进行贝叶斯统计分析，以检验蓝藻水华污染是非酒精性肝病潜在危险因素这一假设。
采用生态研究设计，计算了1999年至2010年美国各县非酒精性肝病的性别和年龄标准化死亡率（SMR）。根据2005年8月1日至2005年9月30日MERIS（中分辨率成像光谱仪）水色图像估计的藻蓝蛋白水平制作水华覆盖图。使用扫描统计工具识别非酒精性肝病死亡的显著聚集区。利用空间关联局部指标（LISA）聚类图和贝叶斯空间回归模型分析蓝藻水华覆盖与非酒精性肝病死亡之间的关系。
发现蓝藻水华在美国广泛分布，包括沿海地区；3109个县中有62%（1949个）显示出用MERIS测量的蓝藻水华迹象。在受蓝藻水华影响的沿海地区发现了非酒精性肝病死亡的显著聚集区。贝叶斯回归分析表明，水华覆盖与非酒精性肝病死亡风险显著相关。在调整年龄、性别、教育水平和种族后，受影响县的水华覆盖每增加1%，非酒精性肝病风险增加0.3%（95%CI，0.1%至0.5%）。
在人群水平上，美国本土蓝藻水华与非酒精性肝病之间存在统计学上的显著关联。基于遥感的水质监测为评估健康危害提供了一个有用的工具，但需要更多研究来确定蓝藻水华与肝病之间的具体关联。
