# Poor quality

Symbol according to Commission implementing decision of 27 May 2011 (2011/321/EU)

The European regulation DIRECTIVE 2006/7/EC

defines

as follows:**poor quality**

Bathing waters are to be classified as ‘poor’ if, in the set of bathing water quality data for the last assessment periodNOTES^{(a)}, the percentile values^{(b)}for microbiological enumerations are worse^{(c)}than the ‘sufficient’ values set out in Annex I, column D.

( ^{a})‘Last assessment period’ means the last four bathing seasons or, when applicable, the period specified in Article 4(2) or (4). ( ^{b})Based upon percentile evaluation of the log _{10}normal probability density function of microbiological data acquired from the particular bathing water, the percentile value is derived as follows:(i) Take the log _{10}value of all bacterial enumerations in the data sequence to be evaluated. (If a zero value is obtained, take the log_{10}value of the minimum detection limit of the analytical method used instead.)(ii) Calculate the arithmetic mean of the log _{10}values (μ).(iii) Calculate the standard deviation of the log _{10}values (σ).The upper 90‑percentile point of the data probability density function is derived from the following equation: upper 90‑percentile = antilog (μ + 1,282 σ). The upper 95‑percentile point of the data probability density function is derived from the following equation: upper 95‑percentile = antilog (μ + 1,65 σ). ( ^{c})‘Worse’ means with higher concentration values expressed in cfu/100 ml.

Excerpt from Article 5(4)(a):

in respect of each bathing water classified as ‘poor’, the following measures shall be takenwith effect from the bathing season that follows its classification:

- adequate management measures,
includingabathing prohibitionoradvice against bathing, with a view to preventing bathers' exposure to pollution;