### 1



## Appendix B.5: Comparison of NEEAR culturable water quality and health

effects to EPA’s epidemiology studies from the 1980s : MEMO - NEEAR

culture compared to 1980s data.

### 2 Cover Memo for Appendix B.5 Comparison of NEEAR culturable water quality and health

effects to EPA’s epidemiology studies from the 1980s : MEMO - NEEAR culture compared

to 1980s data.

Purpose and Limitations of analysis in Appendix B.5

The analysis described in Appendix B.5 was developed to evaluate whether the NEEAR culture

data are consistent with the culture data used to develop the 1986 criteria. The raw data

underlying the 1986 analyses have been lost over time. Only the summary statistics for the ol der

data , as published in the 1986 criteria document and supporting documentation are available

. Therefore EPA was not able to replicat e the more modern statistical analyses that were used to

evaluate the NEEAR data on the older data set

.

Th e analyses in Appendix B.5 replicate the statistical methods used to evaluate the data that

support the 1986 criteria and were conducted to provide historical perspective and evaluate

whether the two datasets are consistent

. These analyses consider the relative level o f public

health protection provided at the level of water quality specified in the new/revised RWQC.

They do not define a new illness response for culture based FIB. The NEEAR i llness response is

best defined by the more sophisticated analyses published by Wade et al. 2008 and 2010.

### 3



## Comparison of NEEAR culturable water quality and health effects to EPA’s

epidemiology studies from the 1980s : MEMO - NEEAR culture compared to

1980s data

Executive Summary

Objective

Compare observed culturable counts of enterococci and GI illness rates from the 1983/1984 epidemiology

studies and NEEAR epidemiology studies.

Summary

The NEEAR study data are generally consistent with data from 1983/1984 epidemiolog y studies. This

analysis supports the continued use of the 1986 culture-based ambient water quality criteria for

enterococci. However, there are specific conditions under which qPCR enterococci density may be a

substantially better predictor of health effects than culturable enterococci.

Approach

Summarize culturable enterococci data from the NEEAR studies and compare the results to the

1983/1984 studies. Identify similarities and differences between the NEEAR culturable enterococci and

observed health effects data and the data from the 1983/1984 studies.

Results

T he POTW

- impacted marine and freshwater NEEAR study data are qualitatively consistent with the data

from the 1983/1 984 epidemiology studies for culturable enterococci and observed excess GI illness.

When the daily NEEAR data were aggregated by days of similar water quality, there were several

conditions (beaches with low enterococci density and relatively high excess illness) that diverged from

the previous study results. Subsequent investigation indicated that, in contrast to culturable enterococci,

qPCR enterococci densities (for the aggregated data) generally increased with increasing rates of GI

illness. This obs ervation indicates that at certain sites and under specific conditions the qPCR enterococci

density may correspond better to adverse health effect levels than culturable enterococci.

Limitations

These analyses are a limited evaluation of water quality data and are intended to compliment the reported

epidemiological results. These analyses do not account for many of the covariate risk factors considered

in EPA’s epidemiological analyses of NEEAR data such as age of participants, food consumption at the

beach, or contact with sand.

Background

The epidemiological studies that underpin the 1986 Ambient Water Quality Criteria (AWQC) for

recreational waters (Cabelli, 1983; Dufour, 1984) estimate illness levels for recreational water contact

### 4

associated with specific levels of fecal indicator bacteria (U.S. EPA, 1986). The relationships between

observed culturable counts of fecal indicator bacteria (FIB) and predicted illness levels in the 1986

AWQC are based on observed seasonal geometric mean culturable FIB densities and average

gastrointestinal (GI) illness rates from each study site.

EPA’s recent NEEAR studies report statistically significant relationships between qPCR counts (CE

and/or CCE) of enterococci and observed GI illness levels (note there was a change in the definition of GI

illness from the earlier studies and the EPA Office of Research and Development has developed a

translation factor for the different GI illness outcomes) (Wade et al., 2006; Wade et al., 2008; Wade et al.,

2010). The NEEAR studies were designed, in part to address many of the perceived or actual limitations

in the earlier epidemiological studies. For example, new modern statistical and analytical techniques

account for a wide range of covariates at a given level of water quality. Moreover, the NEEAR analyses

are based on daily water quality and health observations rather than seasonal averages (as were used in

the 1983/1984 epidemiological studies). The results from the NEEAR studies indicate that Enterococcus

qPCR levels are a stronger predictor of GI illness than culturable enterococci. However, swimmers

exposed above the 1986 AWQC culturable values for enterococci did exhibit higher risks than nonswimmers or swimmers exposed below this value (Wade et al., 2008).

Because culturable enterococci is likely to be included as one component of the 2012 new/revised

recreational water quality criteria (RWQC), a relative comparison of the (culturable enterococci) results

from the 1983/1984 and NEEAR epidemiology studies is important. However, as indicated above, the

NEEAR studies employed different statistical methods compared to those reported in the 1980s, and a

direct comparison of the results was not possible using the published results. Thus, this memorandum

summarizes work to compile the NEEAR culturable enterococci data in a manner that is directly

comparable to the 1983/1984 epidemiology studies and evaluate those comparisons. Tabular and

graphical data summaries provide insights about the relative similarities and differences between the

study results.

Methods

Water quality and health data from the NEEAR studies were provided by EPA ORD. Those data were

consolidated into Excel spreadsheets. Tabular and graphical data summaries were then generated based

on aggregation of the data by day, season, and days of similar culturable enterococci densities (water

quality). The purpose of aggregating data by days of similar water quality was to balance the benefits and

drawbacks of the daily and seasonal data. These aggregated data (by days of similar water quality)

increase the robustness of water quality and health data over daily data while simultaneously increasing

resolution over seasonal data.

To facilitate a comparison between the NEEAR data and the 1983/1984 epidemiological studies, several

logistical decisions were required:

1. Counts of enterococci reported as 0/100 mL were assigned a log10 value of -1. This assignment

was made to ensure consistency across marine and freshwaters as this was the approach used in

the ORD supplied marine water data files.

2. Non-swimmers were defined as interviewees reporting no water contact.

3. Swimmers were defined as interviewees reporting immersion in the water.

### 5

4. Non-swimmer illness rates were based on all data collected for the beach over the study (illness

rate per 1000 = number of illnesses among non-swimmers at the beach over the course of the

study / number of non-swimmers at the beach over the course of the study x 1000.

5. The highly credible gastrointestinal illness (HCGI) equivalent illness rate was computed as the

NEEAR study GI (NGI) illness rate divided by a factor of 4.5 1



### .

6. The water quality (for each beach day, season, etc.) was characterized by the geometric mean

(GM) of the culturable enterococci from all samples collected during the time period (day,

season, etc.) evaluated.

7. The seasonal-average illness rate (used for the seasonal evaluation) is: 1000 x (total number of

illnesses among swimmers for a given beach over the entire study / total number of swimmers at

the beach during the entire study)

– seasonal average non-swimmer illness rate for the beach.

8. To aggregate data for each beach by days of similar water quality, the following approach was

used:

Data for each beach-day were sorted by the observed culturable enterococci geometric

mean.

Groups of days with similar culturable enterococci geometric means were established for

each beach as a first prioritization for aggregates (bins).

Using the first prioritization described above, aggregates were then constructed to the

extent possible to contain a similar number of study participants.

For each bin, the water quality is represented by the geometric mean of enterococci

densities (CFU/100mL) for study days within the bin (because enterococci is lognormally distributed in water) and the illness rate is the arithmetic mean of all

illnesses observed for study days within the bin.

Results

Aggregation by study day

Tabular results for data aggregated by study day from each of the seven beaches are provided in Tables 1

through 7. In those tables, the “ill proportion among swimmers”, “ill proportion among non

- swimmers”,

“excess NGI based on daily non

- swimmer illness rate”, and “excess NGI based on beach average

(seasonal) non- swimmer illness rate” were computed based on the other data report ed in the Tables.

Daily excess illness (expressed as HCGI equivalent) based on the beach average non-swimmer illness

rate 2 

### is plotted against daily the enterococci density geometric mean for NEEAR freshwater and marine

water study sites in Figures 1 and 2, respectively.

1 Based on pr eviously mentioned analysis by EPA ORD

2 The daily average non-swimmer illness rate (also shown in Tables 1-7) is a less robust estimate and is particularly sensitive to

the daily number of non-swimmers reporting GI illness which is typically small (in many cases <10)

### 6

Table 1. Huntington Beach

Beach DatesDaily geometric meanenterococcidensity(CFU/100 mL)1Total numberinterviewed2Number reporting nowater contactNumber reportingimmersionNumber reportingNGI,no contactNumber reportingNGI,immersionIll proportion (#/1000)among non-swimmersIll proportion (#/1000)among swimmersExcess NGI, swimmers(#/1000), dailynonswimmer illnessrateExcess NGI, swimmers(#/1000), beach averagenonswimmer illnessrate

HB 8/2/2003 28.9 188 77 76 12 8 155.84 105.26

- 50.58 9.50

HB 8/3/2003 66.4 122 88 7 9 1 102.27 142.86 40.58 47.09

HB 8/9/2003 40.4 169 83 53 11 5 132.53 94.34

- 38.19

- 1.43

HB 8/10/2003 55.4 295 131 100 9 15 68.70 150.00 81.30 54.23

HB 8/16/2003 12.2 183 97 50 10 9 103.09 180.00 76. 91 84.23

HB 8/23/2003 7.8 252 143 71 9 11 62.94 154.93 91.99 59.16

HB 8/24/2003 5.2 307 144 105 19 11 131.94 104.76

- 27.18 9.00

HB 8/30/2003 290.7 264 165 36 17 7 103.03 194.44 91.41 98.68

HB 8/31/2003 9.6 293 170 80 12 14 70.59 175.00 104.41 79.23

HB 9/6/2003 4.0 158 105 23 7 1 66.67 43.48

- 23.19

- 52.29

HB 9/7/2003 4.9 266 177 58 17 6 96.05 103.45 7.40 7.68

HB 9/13/2003 11.0 155 77 41 9 5 116.88 121.95 5.07 26.19

HB 9/14/2003 10.3 188 78 57 6 8 76.92 140.35 63.43 44.59

1 Typically based on 18 -27 data points

2 Total number interviewed = Number reporting no contact + number reporting immersion + number reporting wading (not shown)

### 7

Table 2. West Beach

Beach DatesDaily geometric meanenterococcidensity(CFU/100 mL)1Total numberinterviewed2Number reporting nowater contactNumber reportingimmersionNumber reportingNGI, no contactNumber reportingNGI, immersionIll proportion(#/1000) among nonswimmersIll proportion(#/1000) amongswimmersExcess NGI,swimmers (#/1000),daily nonswimmerillness rateExcess NGI,swimmers (#/1000),beach averagenonswimmer illnessrate

WB 6/1/2003 27.9 43 33 3 2 0 60.61 0.00

- 60.61

- 49.86

WB 6/7/2003 1.4 186 97 46 6 1 61.86 21.74

- 40.12

- 28.12

WB 6/8/2003 6.8 58 34 7 0 1 0.00 142.86 142.86 93.00

WB 6/14/200 3 1.3 104 66 18 4 1 60.61 55.56

- 5.05 5.69

WB 6/15/2003 2.3 172 91 58 4 5 43.96 86.21 42.25 36.35

WB 6/21/2003 0.8 85 37 30 2 7 54.05 233.33 179.28 183.47

WB 6/22/2003 1.0 148 19 112 1 9 52.63 80.36 27.73 30.50

WB 6/28/2003 10.6 66 31 23 0 1 0.00 43.48 43.48

- 6.38

WB 6/29/2003 9.5 145 35 84 1 12 28.57 142.86 114.29 93.00

WB 7/4/2003 26.7 139 27 107 2 7 74.07 65.42

- 8.65 15.56

WB 7/5/2003 13.6 160 20 114 0 6 0.00 52.63 52.63 2.77

WB 7/6/2003 3.0 134 11 96 0 13 0.00 135.42 135.42 85.56

WB 7/12/2003 1 .6 201 25 134 3 19 120.00 141.79 21.79 91.93

WB 7/13/2003 5.6 123 9 99 0 2 0.00 20.20 20.20

- 29.66

WB 7/19/2003 1042.1 226 47 135 3 12 63.83 88.89 25.06 39.03

WB 7/20/2003 21.1 281 41 189 4 21 97.56 111.11 13.55 61.25

WB 7/26/2003 37.5 243 27 179 1 28 37.04 156.42 119.39 106.56

WB 7/27/2003 34.5 84 43 30 1 2 23.26 66.67 43.41 16.81

WB 8/2/2003 11.7 174 15 141 1 17 66.67 120.57 53.90 70.71

WB 8/3/2003 3.2 92 14 62 1 5 71.43 80.65 9.22 30.78

### 8

Table 3. Silver Beach

Beach DatesDaily geometric meanenterococcidensity(CFU/100 mL)1Total numberinterviewed2Number reporting nowater contactNumber reportingimmersionNumber reportingNGI,no contactNumber reportingNGI,immersionIll proportion (#/1000)among non-swimmersIll proportion (#/1000)among swimmersExcess NGI, swimmers(#/1000), dailynonswimmer illnessrateExcess NGI, swimmers(#/1000), beach averagenonswimmer illnessrate

SB† 6/26/2004 5.7 409 162 156 10 10 61.73 64.10 2.37 8.38

SB 6/27/2004 11.1 466 115 281 5 18 43.48 64.06 20.58 8. 34

SB 7/3/2004 17.3 622 91 402 7 32 76.92 79.60 2.68 23.88

SB 7/4/2004 185.6 325 252 30 5 5 19.84 166.67 146.83 110.95

SB 7/5/2004 14.0 599 296 222 16 17 54.05 76.58 22.52 20.86

SB 7/10/2004 8.5 455 58 334 6 27 103.45 80.84

- 22.61 25.12

SB 7/11/2004 2 4.6 566 75 409 7 31 93.33 75.79

- 17.54 20.07

SB 7/17/2004 29.5 618 234 279 14 31 59.83 111.11 51.28 55.39

SB 7/18/2004 50.0 603 204 327 12 22 58.82 67.28 8.45 11.56

SB 7/24/2004 59.5 554 220 190 13 12 59.09 63.16 4.07 7.44

SB 7/25/2004 80.4 474 194 156 10 12 51.55 76.92 25.38 21.20

SB 7/31/2004 104.3 128 104 7 7 0 67.31 0.00

- 67.31

- 55.72

SB 8/1/2004 47.2 483 76 345 2 35 26.32 101.45 75.13 45.73

SB 8/7/2004 20.8 729 252 359 15 18 59.52 50.14

- 9.38

- 5.58

SB 8/8/2004 17.9 516 101 310 8 22 79.21 70.97

- 8.24 15.25

SB 8/14/2004 55.5 383 138 173 10 14 72.46 80.92 8.46 25.20

SB 8/15/2004 45.5 502 170 246 9 15 52.94 60.98 8.03 5.26

SB 8/21/2004 101.4 443 119 259 3 15 25.21 57.92 32.70 2.19

SB 8/22/2004 22.9 469 243 142 13 18 53.50 126.76 73.26 71.04

SB 9/3/2004 28.3 185 35 116 2 7 57.14 60.34 3.20 4.62

SB 9/4/2004 30.3 561 61 415 3 33 49.18 79.52 30.34 23.80

SB 9/5/2004 127.0 484 96 318 3 28 31.25 88.05 56.80 32.33

SB 9/6/2004 73.1 298 78 175 8 8 102.56 45.71

- 56.85

- 10.01

### 9

Table 4. Washington Park Beach

Beach DatesDaily geometric meanenterococcidensity(CFU/100 mL)1Total numberinterviewed2Number reporting nowater contactNumber reportingimmersionNumber reportingNGI,no contactNumber reportingNGI,immersionIll proportion (#/1000)amongnon-swimmersIll proportion (#/1000)among swimmersExcess NGI, swimmers(#/1000), dailynonswimmer illnessrateExcess NGI, swimmers(#/1000), beach averagenonswimmer illnessrate

WP 6/26/2004 8.36 235 98 93 6 4 61.22 43.01

- 18.21

- 19.84

WP 6/27/2004 9.18 251 72 124 7 15 97.22 120.97 23.75 58.12

WP 7/3/2004 17.9 188 49 104 4 11 81.63 105.77 24.14 42.92

WP 7/4/2004 15.4 187 52 105 3 7 57.69 66.67 8.97 3.82

WP 7/5/2004 95 371 148 167 8 13 54.05 77.84 23.79 15.00

WP 7/10/2004 37.5 215 39 144 3 18 76.9 2 125.00 48.08 62.15

WP 7/11/2004 27.6 184 48 110 5 10 104.17 90.91

- 13.26 28.06

WP 7/17/2004 30.1 172 46 96 4 6 86.96 62.50

- 24.46

- 0.35

WP 7/18/2004 43.0 177 72 87 4 8 55.56 91.95 36.40 29.11

WP 7/24/2004 35.2 154 81 49 4 12 49.38 244.90 195.52 182.0 5

WP 7/25/2004 26.0 209 89 83 3 7 33.71 84.34 50.63 21.49

WP 8/1/2004 7.61 236 28 181 2 11 71.43 60.77

- 10.66

- 2.07

WP 8/7/2004 43.0 234 69 121 6 10 86.96 82.64

- 4.31 19.80

WP 8/8/2004 28.8 276 40 181 3 14 75.00 77.35 2.35 14.50

WP 8/14/2004 39.9 78 4 2 10 1 0 23.81 0.00

- 23.81

- 62.85

WP 8/15/2004 37.4 236 73 132 5 10 68.49 75.76 7.26 12.91

WP 8/21/2004 24.9 169 65 84 1 7 15.38 83.33 67.95 20.49

WP 8/22/2004 22.2 176 33 104 1 9 30.30 86.54 56.24 23.69

WP 9/3/2004 25.7 14 4 8 1 0 250.00 0.00

- 250.00

- 62.85

WP 9/4/2004 14.4 238 37 175 2 18 54.05 102.86 48.80 40.01

WP 9/5/2004 28.4 266 53 165 3 11 56.60 66.67 10.06 3.82

WP 9/6/2004 32.8 78 19 37 3 5 157.89 135.14

- 22.76 72.29

### 10

Table 5. Edgewater Beach

Beach DatesDaily geometric meanenterococcidensity(CFU/100 mL)1Total numberinterviewed2Number reporting nowater contactNumber reportingimmersionNumber reportingNGI,no contactNumber reportingNGI,immersionIll proportion (#/1000)among non-swimmersIll proportion (#/1000)among swimmersExcess NGI, swimmers(#/1000), dailynonswimmer illnessrateExcess NGI, swimmers(#/1000), beach averagenonswimmer illnessrate

EB 6/4/2005 23.77 75 24 27 0 7 0.0 259.3 259.3 175.0

EB 6/5/2005 16.76 58 28 13 3 2 107.1 153.8 46.7 69.6

EB 6/18/2005 68.0 6 44 16 6 1 0 62.5 0.0

- 62.5

- 84.2

EB 6/19/2005 15.34 102 37 37 4 4 108.1 108.1 0.0 23.9

EB 6/25/2005 12.01 68 15 31 0 3 0.0 96.8 96.8 12.6

EB 6/26/2005 3.08 79 15 33 0 2 0.0 60.6 60.6

- 23.6

EB 7/2/2005 22.66 67 23 22 2 4 87.0 181.8 94.9 97.6

EB 7/3/2 005 7.77 105 28 24 5 5 178.6 208.3 29.8 124.1

EB 7/4/2005 17.09 92 32 27 4 1 125.0 37.0

- 88.0

- 47.2

EB 7/16/2005 88.75 64 11 34 1 5 90.9 147.1 56.1 62.8

EB 7/17/2005 3.86 40 17 6 1 0 58.8 0.0

- 58.8

- 84.2

EB 7/23/2005 10.78 66 23 22 2 2 87.0 90.9 4.0 6. 7

EB 7/24/2005 3.91 52 17 20 1 0 58.8 0.0

- 58.8

- 84.2

EB 7/30/2005 0.66 98 21 34 1 2 47.6 58.8 11.2

- 25.4

EB 7/31/2005 1.37 79 20 13 5 2 250.0 153.8

- 96.2 69.6

EB 8/6/2005 19.36 47 8 13 0 1 0.0 76.9 76.9

- 7.3

EB 8/7/2005 4.10 49 13 21 0 3 0.0 142.9 14 2.9 58.6

EB 8/13/2005 2.05 58 14 14 0 1 0.0 71.4 71.4

- 12.8

EB 8/14/2005 2.50 38 8 11 1 3 125.0 272.7 147.7 188.5

EB 8/20/2005 1.20 28 9 9 0 0 0.0 0.0 0.0

- 84.2

EB 8/21/2005 4.05 34 1 12 1 0 1000.0 0.0

- 1000.0

- 84.2

### 11

Table 6. Fairhope Beach

Beach Da tesDaily geometricmeanenterococcidensity (CFU/100mL)1Total numberinterviewed2Number reportingno water contactNumber reportingimmersionNumber reportingNGI, no contactNumber reportingNGI, immersionIll proportion(#/1000) amongnon-swimmersIll proportion(#/1000) amongswimmersExcess NGI,swimmers (#/1000),daily nonswimmerillness rateExcess NGI,swimmers (#/1000),beach averagenonswimmer illnessrate

FB† 5/19/2007 15.07 154 85 33 8 1 94.12 30.30

- 63.81

- 56.45

FB 5/20/2007 2.69 183 98 4 4 12 3 122.45 68.18

- 54.27

- 18.57

FB 5/25/2007 6.71 81 47 11 4 0 85.11 0.00

- 85.11

- 86.75

FB 5/26/2007 8.43 145 64 50 3 2 46.88 40.00

- 6.88

- 46.75

FB 5/27/2007 13.80 126 28 54 2 5 71.43 92.59 21.16 5.84

FB 5/28/2007 13.76 100 35 30 6 2 171.43 66.67

- 10 4.76

- 20.09

FB 6/2/2007 230.10 106 48 37 4 3 83.33 81.08

- 2.25

- 5.67

FB 6/3/2007 27.05 73 26 16 2 2 76.92 125.00 48.08 38.25

FB 6/9/2007 25.41 64 28 17 1 2 35.71 117.65 81.93 30.89

FB 6/10/2007 18.88 99 28 43 1 1 35.71 23.26

- 12.46

- 63.50

FB 6/16/2007 78.55 110 46 44 3 8 65.22 181.82 116.60 95.07

FB 6/17/2007 143.73 104 57 24 4 0 70.18 0.00

- 70.18

- 86.75

FB 6/23/2007 23.00 66 22 27 1 3 45.45 111.11 65.66 24.36

FB 6/24/2007 76.43 57 22 19 5 5 227.27 263.16 35.89 176.41

FB 6/30/2007 27.44 49 22 11 0 3 0.00 272.73 272.73 185.97

FB 7/1/2007 10.02 71 22 34 2 7 90.91 205.88 114.97 119.13

FB 7/4/2007 45.61 97 39 37 4 4 102.56 108.11 5.54 21.36

FB 7/7/2007 10.45 43 12 16 0 2 0.00 125.00 125.00 38.25

FB 7/8/2007 48.85 78 28 34 1 0 35.71 0.00

- 35.71

- 86.7 5

FB 7/14/2007 70.22 50 19 22 1 1 52.63 45.45

- 7.18

- 41.30

FB 7/15/2007 59.71 27 7 8 1 1 142.86 125.00

- 17.86 38.25

FB 7/21/2007 12.20 25 11 8 1 0 90.91 0.00

- 90.91

- 86.75

FB 7/22/2007 6.88 55 28 11 4 4 142.86 363.64 220.78 276.88

FB 7/28/2007 14.59 2 2 7 11 0 3 0.00 272.73 272.73 185.97

FB 7/29/2007 4.72 30 24 4 4 0 166.67 0.00

- 166.67

- 86.75

### 12

Table 7. Goddard Beach

Beach DatesDaily geometric meanenterococcidensity(CFU/100 mL)1Total numberinterviewed2Number reporting nowater contactNumberreportingimmersionNumber reportingNGI, no contactNumber reportingNGI, immersionIll proportion(#/1000) among nonswimmersIll proportion(#/1000) amongswimmersExcess NGI,swimmers (#/1000),daily nonswimmerillness rateExcess NGI,swimmers (#/1000),beach averagenonswimmer illnessrate

GB 6/23/2007 3.26 160 98 21 4 0 40.82 0.00

- 40.82

- 46.09

GB 6/24/2007 1.03 170 105 28 4 3 38.10 107.14 69.05 61.06

GB 6/30/2007 1.29 119 64 25 5 2 78.13 80.00 1.88 33.91

GB 7/1/2007 6.29 156 108 19 3 2 27.78 10 5.26 77.49 59.18

GB 7/4/2007 4.90 200 118 54 5 1 42.37 18.52

- 23.85

- 27.57

GB 7/7/2007 4.29 135 63 31 0 0 0.00 0.00 0.00

- 46.09

GB 7/8/2007 0.71 184 58 95 1 3 17.24 31.58 14.34

- 14.51

GB 7/14/2007 1.95 151 65 48 0 4 0.00 83.33 83.33 37.25

GB 7/15/2007 0.61 162 64 61 5 7 78.13 114.75 36.63 68.67

GB 7/21/2007 4.89 74 49 9 2 0 40.82 0.00

- 40.82

- 46.09

GB 7/22/2007 2.32 146 83 38 5 4 60.24 105.26 45.02 59.18

GB 7/28/2007 4.83 90 35 40 0 1 0.00 25.00 25.00

- 21.09

GB 7/29/2007 2.94 63 31 12 1 0 32.26 0.0 0

- 32.26

- 46.09

GB 8/4/2007 10.23 144 34 79 0 8 0.00 101.27 101.27 55.18

GB 8/5/2007 22.95 156 72 53 5 4 69.44 75.47 6.03 29.39

GB 8/11/2007 2.88 81 42 16 4 0 95.24 0.00

- 95.24

- 46.09

GB 8/12/2007 2.26 101 36 33 3 3 83.33 90.91 7.58 44.82

GB 8/18/2007 2.91 87 64 8 1 0 15.63 0.00

- 15.63

- 46.09

GB 8/19/2007 3.05 77 67 3 5 0 74.63 0.00

- 74.63

- 46.09

GB 8/25/2007 3.28 73 21 27 1 0 47.62 0.00

- 47.62

- 46.09

GB 8/26/2007 1.78 103 71 23 4 2 56.34 86.96 30.62 40.87

GB 9/1/2007 38.72 65 57 3 3 0 52.63 0.00

- 52.63

- 46.09

GB 9/2/2007 6.32 101 80 5 5 1 62.50 200.00 137.50 153.91

GB 9/3/2007 13.66 170 99 48 7 3 70.71 62.50

- 8.21 16.41

### 13

Figure 1 . Daily excess HCGI vs. daily Enterococcus density geometric mean for NEEAR freshwater

beaches.

HCGI assumed equal to NGI rate / 4.5.

Excess illness rate is calculated as illness rate among swimmers reporting immersion minus the average illness rate among nonswimmers (reporting no contact) for the beach over the entire study period.



### Fi gure 2. Daily excess HCGI vs. daily Enterococcus density geometric mean for NEEAR temperate

POTW-impacted marine beaches.

HCGI assumed equal to NGI rate / 4.5.

Excess illness rate on each beach day calculated as illness rate among swimmers reporting immersion minus the average illness

rate among non-swimmers (reporting no contact) for the beach over the entire study period.

### 14

Aggregation by season

Tabular results for data aggregated by season from each of the seven beaches are provided in Table 8.

Seasonal average excess illness (expressed as NGI/4.5 = HCGI equivalent) is plotted against seasonal

average Enterococcus density geometric mean for NEEAR freshwater and marine water study sites in

Figures 3 and 4, respectively.

Table 8. Seasonal average water quality and illness rates for NEEAR beaches

Beach Water

quality Participant breakdown NGI

(# ) NGI rate

(# / 1000) Excess

illness rate

(#/1000)

(illness rate

-

non

swimmer

illness rate)Seasonal GM ENT(CFU/100 mL)All samplesTotal # interviewedNo water contactSwimmers(immersionreported)No contactImmersionNo contactImmersionExcess NGI / 1000Excess HCGIequivalent, /1000



### Fresh

Huntington

Beach 17.5 2840 1535 757 147 101 95.8 133.4 37.7 8.4

West Beach 7.9 2865 72 2 1668 36 170 49.9 101.9 52.1 11.6

Silver

Beach 33.1 10872 3374 5651 188 430 55.7 76.1 20.4 4.5

Washington

Park Beach 27.7 4344 1257 2360 79 206 62.8 87.3 24.4 5.4

Marine

Edgewater

Beach 7.3 1343 380 429 32 47 84.2 109.6 25.3 5.6

Fairhope

Beach 22.1 2 015 853 645 74 62 86.8 96.1 9.4 2.1

Goddard

Beach 3.6 2968 1584 779 73 48 46.1 61.6 15.5 3.4

Excess illness rate based on season-average non-swimmer illness rate at each beach to ensure that small sample sizes

of non-swimmer illness rate do not bias excess illness from swimming

. Use of daily illness rate among non-swimmers to determine daily excess illness rate was assessed but not reported.

### 15

Figure 3 . Seasonal average freshwater NEEAR study data and 1986 freshwater study data (season

averages).

Figure 4 . Seasonal average marine NEEAR study data and 1986 marine water study data (season

averages).

Aggregation by study days of similar culturable enterococci

Tabular results for data aggregated by days of similar culturable enterococci from each of the seven

beaches are provided in Table 9. As illustrated in Table 9, aggregation as described previously generally

resulted in four bins per beach (with typically 3 to 7 days per bin). Silver Beach had to be split into five

bins because of the heterogeneity of the observations with reported densities above 30 cfu/100mL, and

Goddard Beach was split into two bins because most observations (20/24) had very low reported

enterococci densities (<7 cfu/100mL). Average excess illness rate (expressed as HCGI equivalent) is

plotted against enterococci density geometric mean for NEEAR freshwater and marine water study sites

aggregated by study days of similar culturable enterococci in Figures 5 and 6, respectively.

### 16

Table 9. Average water quality and illness rates for NEEAR data aggregated by days of similar

water quality

### 17

Figure 5 Freshwater NEEAR data aggregated by similar water quality and 1986 freshwater data

(season averages).

NEEAR study data presented as colored symbols (West Beach green, Huntington Beach red, Silver Beach blue,

Washington Park yellow),

1986 freshwater study data presented as black circles,

1986 freshwater study regression presented as solid lin e.



### Figure 6 Marine NEEAR data aggregated by similar water quality and 1986 marine water study

data (season averages).

NEEAR study data presented as colored symbols (Edgewater green, Fairhope red, Goddard blue),

1986 marine water study data presented as black circles,

1986 marine water study regression presented as solid line regression presented as solid line

### 18

Interpretation of Results

NEEAR study daily geometric mean culturable enterococci were highly variable in both marine and

freshwaters (Refer to Figures 1 and 2). Previously reported epidemiological results (Wade et al., 2008)

indicate that in freshwater, swimmers exposed to waters with culturable enterococci levels above the

AWQC values had higher risks than non-swimmers or swimmers exposed below this value. Direct

comparison of daily data to the epidemiological results from the 1980s was not possible because daily

data were not available from the 1980s studies.

In comparing the seasonal average freshwater NEEAR study data with the 1986 freshwater study data

(Figure 3), three of four points appear consistent, whereas one data point (West Beach) is divergent from

the rest of the data. Culturable enterococci data from the NEEAR marine water studies were in the same

range as the marine water quality data from the 1980s (Figure 4). However, the GI illness rates from the

NEEAR marine water studies appear to be at the low end or slightly lower than those from the marine

water epidemiology studies conducted in the 1980s.

When data aggregated by days of similar culturable enterococci from each of the seven beaches are

compared to the water quality and epidemiology data from the 1980s (Figures 5 and 6), several interesting

observations emerge: 1) Most of the data from freshwater beaches are relatively consistent with the data

from the 1980s (the observed health effects fall in the expected range based on culturable enterococci

levels), 2) One data point from West Beach and one data point from Huntington Beach deviate from all

other NEEAR data and data from the 1980s (low observed enterococci levels and high adverse health

effects rates). These data points could be of particular concern because they represent conditions in

which culturable enterococci levels are low (<10cfu/100mL), yet observed GI illness rates are relatively

high (>12 HCGI/1000 events), 3) data from marine water beaches are relatively consistent with the water

quality data and observed GI illness trends from the 1980s except that the observed levels of GI illness are

generally at the lower end of that observed during the studies from the 1980s.

To further evaluate the potential underlying nature of the divergent data points identified above (Figure

5), we evaluated ancillary data in the provided data tables provided by ORD (antecedent rainfall, wind,

tides, etc.) to determine if trends existed related to low enterococci densities and high adverse health

effect levels. However, no obvious explanation was revealed for the low enterococci densities and high

adverse health effect levels. We then investigated whether qPCR enterococci performed similarly to

culturable enterococci. To facilitate this comparison, we plotted the geometric mean of the qPCR

enterococci densities (CCE/100mL) for study days within the bin against the ar ithmetic mean illness rate

for study days within the bin (the bins were not changed, and thus represent days of low, moderately low,

moderately high, or high culturable enterococci). Those results are presented for NEEAR freshwater and

marine beaches in Figures 7 and 8, respectfully. The combined results for NEEAR freshwater and marine

beaches together are presented in Figure 9. Inspection of the data presented in Figures 7 through 9 clearly

indicate that the qPCR densities (of the data aggregated by days of similar water quality) generally

increased with increasing rates of GI illness and do not contain divergent points from this general trend

(in contrast to culturable enterococci as illustrated in Figure 5). This finding could be of particular

interes t and could provide previously unavailable insights for public health protection for conditions at

### 19

specific beaches where culturable enterococci densities are observed to be low while qPCR densities are

substantially higher.

Figure 7 Freshwater NEEAR qPCR results binned by days of similar culturable enterococci

(West Beach green, Huntington Beach red, Silver Beach blue, Washington Park yellow)

Figure 8 Marine water NEEAR qPCR results binned by days of similar culturable enterococci

Edgewater green, Fairhope red, Goddard blue

### 20

Figure 9 Combined Freshwater and Marine NEEAR qPCR results binned by days similar

culturable enterococci

West Beach green, Huntington Beach red, Silver Beach blue, Washington Park yellow, Edgewater grey

square, Fairhope grey triangle, Goddard grey circle

Conclusions

T he POTW

- impacted NEEAR study culturable enterococci data are generally consistent with the data

from the 1980s for culturable enterococci and observed excess GI illness. When the daily NEEAR data

were aggregated by days of similar culturable enterococci, there were several conditions (freshwater

beaches with low enterococci density and relatively high excess illness) that deviated from the rest of the

results. Subsequent investigation indicated that, in contrast to culturable enterococci, qPCR enterococci

densities (of the aggregated data) generally increased with increasing rates of GI illness. This observation

indicates that at select sites and under specific conditions the qPCR enterococci density may better

c orrespond to adverse health effect levels than culturable enterococci.

References

Cabelli, V.J. (1983) Health effects criteria for marine recreational waters. USEPA Cincinnati, OH.

Dufour, A. (1984) Health effects criteria for fresh recreational waters. US EPA Cincinnati, OH.

U.S. EPA (1986) Ambient water quality criteria for bacteria, Office of Water, EPA440/5-84-

002,Washington, DC,

Wade, T.J., Calderon, R.L., Sams, E., Beach, M., Brenner, K.P., Williams, A.H., and Dufour, A.P. (2006)

Rapidly measured indicators of recreational water quality are predictive of swimming-associated

gastrointestinal illness. Environ Health Perspect 114( 1 ) : 24-28.

### 21

Wade, T.J., Calderon, R.L., Brenner, K.P., Sams, E., Beach, M., Haugland, R., Wymer, L., and Dufour,

A.P. (2008) High sensitivity of children to swimming-associated gastrointestinal illness: results using a

rapid assay of recreational water quality. Epidemiology 19( 3 ) : 375-383.

Wade, T.J., Sams, E., Brenner, K.P., Haugland, R., Chern, E., Beach, M., Wymer, L., Rankin, C.C., Love,

D., Li, Q., Noble, R., and Dufour, A.P. (2010) Rapidly measured indicators of recreational water quality

and swimming-associated illness at marine beaches: A prospective cohort study. Environ Health 9( 1 ) : 66.