Beach Lab Data - DNA Tests

The Chicago Park District tests water samples at beaches along Chicago's Lake Michigan lakefront, which it tests for E. coli in order to monitor swimming safety. Multiple samples may be taken from a beach and samples may be tested by culture, DNA testing, or both.

What do these numbers mean?

The modeling prediction numbers forecast real-time Escherichia coli (E. coli) bacteria levels present in the water. The Chicago Park District (CPD) in partnership with the US Geological Survey, has developed statistical prediction models by using weather data pulled from CPD buoys (https://data.cityofchicago.org/d/qmqz-2xku) and weather stations (https://data.cityofchicago.org/d/k7hf-8y75). E. coli is an indicator species for the presence of disease-causing bacteria, viruses, and protozoans that may pose health risks to the public.

The culture based testing numbers indicate E. coli levels present in the water. This method requires 18-24 hours of processing to receive results. US Environmental Protection Agency (USEPA) recommends notifying the public when E. coli bacteria levels are above the federal water quality Beach Action Value (BAV), which is 235*CFU. When bacteria levels exceed 235 CFU, a yellow or red flag will be implemented. This standard is used at beaches throughout the Great Lakes region. For more information please refer to the USEPA Recreational Water Quality Criteria.

The rapid testing method (qPCR analysis) is a new method that measures levels of pathogenic DNA in beach water. Unlike the culture based test that requires up to 24 hours of processing, the new rapid testing method requires a few hours for results. The Chicago Park District can use results of the rapid test to notify the public when levels exceed UPEPA recommended levels. US Environmental Protection Agency (USEPA) recommends notifying the public when DNA bacteria levels are above the federal water quality Beach Action Value (BAV), which is 1000*CCE. When DNA bacteria levels exceed 1000 CCE, a yellow or red flag will be implemented. For more information please refer to the USEPA Recreational Water Quality Criteria (http://water.epa.gov/scitech/swguidance/standards/criteria/health/recreation).

* The unit of measurement for Escherichia coli is Colony Forming Units (CFU) per 100 milliliters of water.
*The unit of measuring DNA is Enterococci Calibrator Cell Equivalents (CCE) per 100 milliliters of water.

芝加哥公园区对芝加哥密歇根湖湖滨的沙滩水样进行检测，以监测游泳安全。对同一沙滩可能采集多个样本，并通过培养、DNA检测或两者结合的方式进行测试。

这些数字意味着什么？

基于模型预测的数字预报了水中实时大肠杆菌（E. coli）细菌水平。芝加哥公园区（CPD）与美国地质调查局合作，利用从CPD浮标（https://data.cityofchicago.org/d/qmqz-2xku）和气象站（https://data.cityofchicago.org/d/k7hf-8y75）获取的气象数据，开发了统计预测模型。大肠杆菌是致病细菌、病毒和原虫存在的指示物种，这些病原体可能对公众健康构成风险。

基于培养的测试数字表示水中存在的大肠杆菌水平。此方法需要18-24小时的处理时间才能获得结果。美国环境保护署（USEPA）建议，当大肠杆菌细菌水平超过联邦水质海滩行动值（BAV），即235*CFU时，应通知公众。当细菌水平超过235 CFU时，将实施黄色或红色旗帜。这一标准在五大湖地区的海滩上得到应用。有关更多信息，请参阅USEPA的娱乐用水质量标准。

快速检测方法（qPCR分析）是一种新的方法，用于测量海滩水中病原DNA的水平。与需要长达24小时处理时间的基于培养的测试不同，新的快速测试方法只需几小时即可得到结果。芝加哥公园区可以使用快速测试的结果，在水平超过UPEPA推荐水平时通知公众。美国环境保护署（USEPA）建议，当DNA细菌水平超过联邦水质海滩行动值（BAV），即1000*CCE时，应通知公众。当DNA细菌水平超过1000 CCE时，将实施黄色或红色旗帜。有关更多信息，请参阅USEPA的娱乐用水质量标准（http://water.epa.gov/scitech/swguidance/standards/criteria/health/recreation）。

大肠杆菌的测量单位为每100毫升水中的菌落形成单位（CFU）。
DNA的测量单位为每100毫升水中的粪肠球菌校准细胞当量（CCE）。