109

Wednesday, March 16

8:00 a.m.–9:45 a.m.

Session V: 

Epidemiological Studies: What Does 

the Science Tell Us?
110

U.S. EPA’s National Beach Conference

Indicators of Water Quality and Health 

Effects at a Tropical and a Runoff 

Impacted Beach

Tim Wade

U.S. EPA Office of Research and Development

Abstract

Background: Studies conducted by EPA 

at beaches with nearby treated sewage discharges established associations between 

gastrointestinal (GI) illnesses among swimmers 

and measurements of fecal indicator bacteria, 

Enterococcus, and Bacteroidales (marine beaches 

only) measured by quantitative polymerase 

chain reaction (qPCR). In 2009, EPA conducted 

studies at one beach in a tropical climate 

(Puerto Rico) and a second beach influenced by 

“urban runoff” (South Carolina). The goal was 

to examine water quality and illnesses among 

swimmers.

Methods: Beachgoers were enrolled and 

upon leaving answered questions regarding 

swimming exposures. Ten to twelve days later 

they were asked about new illness symptoms. 

Six water samples were collected three times a 

day and tested for fecal indicator bacteria.

Results: At the Puerto Rico beach, 15,726 

individuals were enrolled. Swimmers reported 

higher rates of rash. Densities of fecal indicator 

bacteria were low and no single day exceeded 

EPA criteria for Enterococcus. In addition, the 

qPCR assay showed evidence of interference 

or inhibition. Consistent health relationships 

between fecal indicator organisms and swimming-associated illness were not established. 

At the South Carolina beach, 11,159 individuals were enrolled. Swimmers reported higher 

rates of rash, GI illness, and earache. Only one 

day exceeded EPA criteria for Enterococcus. 

Consistent health relationships between fecal 

indicator organisms and swimming-associated 

illness were also not established.

Conclusions: At a tropical beach and a 

beach impacted by urban runoff, associations 

between illnesses among swimmers and water 

quality were not established. Possible explanations include better than expected water quality, qPCR interference or inhibition, and lack of 

human fecal contamination.

This is an abstract of a proposed presentation and does not necessarily represent EPA 

policy.

Biosketch

Dr. Tim Wade is an epidemiologist with 

EPA’s Office of Research and Development 

(ORD), Human Studies Division, in Chapel 

Hill, North Carolina. He received his Master of 

Public Health in Epidemiology and Biostatistics 

in 1998 from the University of California, 

Berkeley, and his PhD in Epidemiology in 2002, 

also from the University of California, Berkeley. 

He joined EPA ORD in 2003 as a post doc, and 

was recently named Chief of the Epidemiology 

Branch. His research focuses on quantifying 

and measuring the health effects of waterborne 

contaminants. Dr. Wade holds an adjunct 

appointment in the Epidemiology Division at 

the University of North Carolina.
111

Day Two: Session V
112

U.S. EPA’s National Beach Conference
113

Day Two: Session V
114

U.S. EPA’s National Beach Conference
115

Day Two: Session V
116

U.S. EPA’s National Beach Conference

Rapid Indicators for Enterococcus and the 

Risk of Illness after Exposure to Urban Runoff 

Contaminated Marine Water: Results from a 

“Natural Experiment”

Presenter: Jack Colford

University of California, Berkeley, School of Public Health

Authors: Jack Colford, Ken Schiff, John Griffith, Vince Yau, Catherine Wright, Benjamin 

Arnold, Joshua Gruber, Tim Wade, Charles McGee, Mark Gold, Steve Weisberg

Abstract

Traditional fecal indicator bacteria (FIB) 

culture methods are too slow to provide timely 

warnings to swimmers of potential health risks. 

We assessed the relationship between swimming-related illnesses and both traditional and 

new, rapid methods of detection using qPCR 

for Enterococcus species. We measured health 

at baseline and 2 weeks later in 9,525 participants at Doheny Beach, California in 2007/08. 

Outcomes were compared for swimmers vs. 

non-swimmers. Among swimmers we compared associations of health to levels of indicators, including both traditional (Enterococcus

by EPA Method 1600 or EnterolertTM, fecal 

coliforms, and total coliforms) and rapid 

(Enterococcus Taqman qPCR, Scorpion 1 qPCR, 

Scorpion 2 qPCR) methods. Beach conditions 

provided a natural experiment—the primary 

source of beach pollution was San Juan Creek, 

which flowed untreated into the ocean for 

weeks following rainfall, but did not flow when 

a sand berm formed across the creek mouth. 

This allowed us to study the impact of markedly different water quality conditions on the 

associations of traditional and rapid FIB measurements with health. We observed significant 

increases in gastrointestinal illness in swimmers compared to non-swimmers, independent 

of the berm. Increasing levels of water exposure 

(body immersion/head emersion/swallowing) 

were associated with increasing risks of illness. 

When the berm was open (poor water quality), 

we observed significant associations between 

illness and both traditional and rapid methods 

for Enterococcus, but not when the berm was 

closed. These results suggest that the association of water quality indicators with illness is 

influenced by the conditions under which the 

indicators are applied.

Biosketch

Dr. Jack Colford is a Professor of 

Epidemiology at the University of California 

(UC), Berkeley, School of Public Health. He 

is a graduate of the Johns Hopkins School of 

Medicine (MD, 1985) and the UC Berkeley 

School of Public Health (PhD, Epidemiology, 

1996). He completed a residency in internal 

medicine and a fellowship in infectious diseases 

at UC, San Francisco. He was Chief Medical 

Resident at Stanford University Hospital and 

completed board-certification in both internal medicine and infectious diseases. He is 

the sole instructor in semester-long courses in 

advanced epidemiologic methods, intervention trial design, and meta-analysis, and was 

selected for multiple teaching awards at UC 

San Francisco, Stanford, and UC Berkeley by 

faculty and students. Dr. Colford has authored 

70 peer-reviewed scientific publications, including numerous articles on waterborne diseases. 

He has been the principal investigator of four 

triple-blinded, randomized controlled trials of 

drinking water and health effects funded by the 

National Institutes of Health, the U.S. Centers 

for Disease Control and Prevention, EPA, and 

the UC. He collaborated with the World Bank 

on a comprehensive review evaluating the 
117

Day Two: Session V

effectiveness of drinking water treatments in 

the developing world. He was also the principal 

investigator of numerous observational studies 

focused on waterborne disease risks. Currently, 

he is the epidemiologist for a suite of water and 

sanitation interventions in India, South Africa, 

Peru, Tanzania, and Vietnam supported by 

the World Bank and the Gates Foundation. He 

is the principal investigator of a new award 

(September 2009) from the Gates Foundation 

for a 5-year, 2-country (Bangladesh and Kenya), 

8-arm randomized controlled trial evaluating 

the single and combined benefits of water, sanitation, and hygiene interventions.
118

U.S. EPA’s National Beach Conference
119

Day Two: Session V
120

U.S. EPA’s National Beach Conference
121

Day Two: Session V
122

U.S. EPA’s National Beach Conference

The BEACHES Study 1: Health Effects from 

Non-point Source Microbial Contaminants in 

Subtropical Recreational Marine Waters

Presenter: Lora Fleming

University of Miami

Authors: Lora Fleming, Jay Fleisher, Jonathan Kish

Abstract

Background: The use of microbial water 

quality indicators to regulate recreational water 

bodies, particularly in sub/tropical recreational 

marine waters without known sources of sewage, has been questioned. The objectives of this 

study were to evaluate the risks to humans from 

exposure to subtropical recreational marine 

waters with no known point source.

Methods: 1,303 adult regular bathers were 

randomly assigned to bather and non-bather 

groups, with subsequent follow-up for reported 

illness, in conjunction with extensive environmental sampling of fecal indicator bacteria (FIB) 

and other indicator organisms.

Results: Bathers were 1.76 times more 

likely to report: gastrointestinal illness (95% 

confidence interval = 0.94–3.30); 4.46 (0.99–20.90) 

for acute febrile respiratory illness; and 5.91 

(2.76–12.63) for a skin illness relative to nonbathers. Among the bathers, a dose-response 

relationship for skin illness was positively 

related to enterococci enumeration by membrane filtration (1.46 [0.97–2.21] per increasing 

log10 unit of enterococci) and positively related 

to 24-hour antecedent rain fall (1.04 [1.01–1.07] 

per increasing millimeters of rain). Acute febrile 

respiratory illness was inversely related to 

water temperature (0.74 [0.56–0.98] per increasing degree of water temperature). There were no 

significant dose response relationships between 

report of human illness and any other FIB or 

environmental measures.

Conclusions: Bathers may be at increased 

risk of several illnesses relative to non-bathers, 

even in the absence of any known source of 

domestic sewage impacting the recreational 

marine waters. There was no dose-response 

relationship between gastrointestinal illness 

and increasing exposure to enterococci, even 

though this is the major outcome illness for 

many current water monitoring standards.

Biosketch

Dr. Lora Fleming is the Director of the 

European Centre of Environment and Human 

Health at the Peninsula College of Medicine 

and Dentistry in Cornwall, England. She 

was the former Co-Director of the National 

Science Foundation/National Institute of 

Environmental Health Services University of 

Miami Oceans and Human Health Center. 

Dr. Fleming received her AB (1978) and 

MD-MPH (1984) from Harvard University; 

her MSc (1979) in the History of Science from 

Imperial College (London University); and 

her PhD (1997) in Epidemiology from Yale 

University. She is a board certified Occupational 

and Environmental Medicine Physician and 

Epidemiologist. She works in the areas of The 

Blue Gym (a campaign and research program to 

facilitate improved awareness and recreational 

use of marine waters), marine and freshwater toxins, and coastal pathogens, as well as 

research and teaching in Occupational and 

Environmental Medicine and Epidemiology. 

Dr. Fleming has published 190 peer-reviewed 

journal papers and book chapters, as well as 

many conference proceedings, books, and 

technical reports. She has also presented her 

research extensively in scientific and other 

venues.
123

Day Two: Session V
124

U.S. EPA’s National Beach Conference
125

Day Two: Session V
126

U.S. EPA’s National Beach Conference
127

Day Two: Session V
128

U.S. EPA’s National Beach Conference
129

Day Two: Session V
130

U.S. EPA’s National Beach Conference
131

Day Two: Session V
132

U.S. EPA’s National Beach Conference

Comparing Swimming-related Illness Associations 

with Fecal Indicators Quantified by qPCR and 

Culture-based Methods at a Freshwater Beach

Presenter: Jiyoung Lee

Ohio State University

Authors: Jiyoung Lee, Jason Marion, Chang Soo Lee, Timothy Buckley

Abstract

Inland waters provide recreational 

benefits to vast portions of the U.S. population. Furthermore, with much attention being 

directed toward rapid indicators of water 

quality, inland water bodies have not been well 

represented. In this study, we engaged in an 

inland Ohio beach cohort study examining relationships between fecal indicators and illness. 

Human health data and culture-based E. coli

densities were obtained across 26 weekend days 

during the 2009 swimming season. Adverse 

health outcomes were reported via phone 

survey 8–9 days post-exposure. Complete data 

during the 23-day period was obtained from 

692 individuals. Multiple fecal indicators were 

also measured via qPCR targeting enterococci 

and other markers (Bacteroides-Prevotella group, 

B. fragilis group, B. fragilis-specific, and tetQ). The 

strength of association between gastrointestinal 

(GI) and highly credible gastrointestinal (HCGI) 

illness for this population was determined via 

logistic regression adjusting for age, gender, 

food at the beach, reservoir inflow and time 

spent at the beach. The culture-based E. coli

levels provided the only significant illness association (highest E. coli quartile group adjusted 

odds ratio [AOR] = 5.14; 95% confidence interval 

[CI] 1.04–25.5). A marginal association (p = 0.08) 

was observed in this quartile with HCGI (AOR 

= 4.11; 95% CI 0.83–20.5). Despite lack of illness 

associations, enterococci and BacteroidesPrevotella markers were correlated (r = 0.474, 

p = 0.022; r = 0.444, p = 0.034) with culture-based 

E. coli methods, respectively. Overall, the water 

quality of the study site was good and the study 

population was small. Given these limitations, 

the traditional E. coli method, albeit not rapid, 

was a better indicator of GI illness at this freshwater beach.

Biosketch

Dr. Jiyoung Lee is an Assistant Professor 

of Environmental Microbiology in the College 

of Public Health, Division of Environmental 

Health Sciences at the Ohio State University. 

She received her BS and MS in Microbiology 

from Seoul National University, and her PhD in 

Environmental Health Sciences from University 

of Michigan. She has worked on beach fecal 

contamination problems, especially rapid detection and contamination sources for the past 

10 years. She has been a faculty member of the 

Ohio State for over 2 years and also has a dual 

appointment at the Department of Food Science 

and Technology. Her main research interests 

are (1) pathways of pathogen transmission in 

water and food, (2) new tools for understanding 

integrative health risks recreational waterborne 

illness, and (3) the impact of climate change on 

infectious agents.
133

Day Two: Session V
134

U.S. EPA’s National Beach Conference
135

Day Two: Session V
136

U.S. EPA’s National Beach Conference
137

Day Two: Session V
138

U.S. EPA’s National Beach Conference
139

Day Two: Session V
U.S. EPA’s National Beach Conference

140

Question & Answer Session

Question 1

Ali Boehm: One thing that seems consistent among urban runoff and nonpoint source studies is the 

importance of including a so-called “event modifier.” Going back to the Haille study in 1999, they used 

distance from the discharge point; in Jack’s [Colford’s] study, it was berm-open, berm-closed; in Laura’s 

[Fleming’s] study, they considered rainfall and tide to some extent. But your study didn’t include any 

event modifiers. I was wondering if you plan to include an environmental scientist or someone who 

has more physical knowledge of your urban runoff site in South Carolina to try and consider some 

event modifiers that might help you better explain your health data. I would just say it seems like a lost 

opportunity if you don’t do that.

Answer 1

Tim Wade: Absolutely, we didn’t do that. Although we didn’t, I’m sure someone with more 

expertise in that could specifically identify what the critical event modifiers would be. We 

did not necessarily have a berm that was either open or closed that lent itself to a natural 

experiment type of study. So, that’s a good suggestion.

Lora Fleming: I just want to add that I was surprised by how little the physical parameters 

actually affected. I mean, we only found one positive association, and it was pretty tiny.

Question 2

David Turbow: Two questions for Dr. Fleming. First, in the study site, you were saying that there was 

no known point source of sewage contamination. Given that there’s an outfall pipe near there, how 

many million gallons per day [mgd] of treated wastewaters is discharged? And second, how long has 

that pipe been in place?

Answer 2

Lora Fleming: I don’t know if I can answer all of this, but Helena [Dr. Solo Gabriele] is here, so 

hopefully she’ll help. The pipe actually goes out 4 miles, and we’ve sampled out along that. 

Also, we’ve looked at the currents and, as far as we can tell, there’s no impact of that particular site on our beach.

Question 2 (follow-up)

David Turbow: How many million gallons of sewage are discharged into those waters and how long 

has that pipe been there?

Comment 2

Helena Solo-Gabriele: I have rough estimates, in the order of hundreds of mgd. But there have 

been expensive studies by NOAA that have shown that that water goes out into the Gulf 

Stream.

Comment 2 (follow-up)

David Turbow: Given that hundreds of mgd are discharged into waters within 5 miles of your 

study site, I think it’s a major threat to the internal validity of your study to claim that there’s 

no known source of sewage there.

Comment 2 (follow-up)

Lora Fleming: Can I just disagree a little bit? All our intensive monitoring has shown that if 

I want to make the Enterococcus levels go up, I go up to the swash zone and I sample there 

at high tide. That has nothing to do with the sewage source that’s several miles away and 

is taken away by the Gulf Stream. However, I haven’t done tracer studies, and your point is 

well-taken.
141

Day Two: Session V

Question 3

John Heffelfinger: I have two administrative, non-science-based, questions for you. For all the panelists, can you give us a general sense of how much these [epidemiology] studies cost? I just have no idea 

of the scope of these things, dollar amount. Of course, there’s a lot of in-kind grad student resources 

involved, too. So, can each of the panelists quickly address that first?

Answer 3

Tim Wade: Our [EPA] studies, being some of the largest and most intense, run over a million 

dollars per beach site, including all the water sampling and testing.

Jack Colford: I’d guess, all-in-all, about $1.5 million total.

Lora Fleming: We did ours on a shoestring, which I wouldn’t recommend to anyone; it was 

about $600,000.

Jiyoung Lee: $250,000 to $300,000.

Question 4

John Heffelfinger: Okay, great, thanks. And then kind of a bureaucratic question, maybe particularly 

for Tim [Wade]. Were any kinds of pre-approvals or clearances required for these studies? I’m thinking 

in particular the Federal Paperwork Reduction Act requirement; what were your experiences there?

Answer 4

Tim Wade: We have a standing Office of Management and Budget (OMB) approval, which 

I don’t believe non-federal people need to get. So that was an additional burden for us, but 

we have an OMB approval under the Paperwork Reduction Act. And then there are human 

subject approvals that we have to run through ethical boards. Does anyone else want to add 

anything?

Comment 4

Lora Fleming: One issue for point source areas in terms of doing a randomized trial like we 

did is that human ethics boards probably will not allow you to do it. So, we were able to do 

it because it was a nonpoint source and because we used only people who regularly bathed 

there.

Jack Colford: We didn’t go down that path because we’re different in California and we were 

fairly certain that our human subjects board wouldn’t consider that.

Tim Wade: I’m not so sure they wouldn’t approve it, because certainly other, more invasive, 

randomized things are approved, like in fields of medicine. But I agree it would raise other 

issues. Especially if you knew, or had a strong idea of, what was in the water at the beach—

like if you knew there were human pathogens at the beach that you were intentionally 

exposing to people, it’d probably come under a lot higher scrutiny, particularly for children.

Question 5

(Unknown): I have two questions. I thought it was very interesting to be able to compare Puerto Rico 

to Miami. What I found interesting about both Puerto Rico and also Miami is that skin and respiratory 

illness came up. I was wondering the opinion of whether this is something that needs to be looked at 

further? Is EPA considering non-GI endpoints?

Answer 5

Tim Wade: Yes, increased skin rash among the swimmers is something that we see—I think 

Jack [Colford] has seen and even written a review paper on this—it’s commonly seen. And 

I’ll be interested to see what Lora [Fleming] has to say about it, but I think the struggle there 

is the causal mechanism for it. The nice thing about the GI is that there’s at least a theoretical, causal basis that I laid out in the first couple of slides. Again, going back to the whole 
U.S. EPA’s National Beach Conference

142

paradigm of the human fecal source that they are marking GI pathogens, but with the skin 

rashes—I think it’s a bigger struggle to make that causal link. You discussed it, at least in 

your paper, I think.

Comment 5

Lora Fleming: One of my problems with the skin is that it’s totally self-reported. If I had a lot 

of money, I would have had a dermatologist looking at them. Also, another factor might be 

in tropical areas, heat-related rash kind of thing as well. And the other thing that Dr. Lee 

mentioned is that there are other organisms out there, and HABs [harmful algal blooms]; for 

example, copepods, and things that we weren’t looking at, and don’t traditionally look at. 

I agree with you, I think that models need to incorporate those much more and not just be 

focused on the endless loop of Enterococcus.

Question 6

(Unknown): But it was interesting to see that both tropical and subtropical studies showed that, which 

is different than the other sites. My second question is related to Ali’s [Boehm’s] question. With the 

other studies, whether physical/chemical parameters were looked at. I was interested in knowing, Tim 

[Wade], in the two studies that you conducted whether that was looked at, and also Dr. Lee, in your 

study as well.

Answer 6

Tim Wade: We do look at those things and we’ll admit, maybe not to the extent that we could 

have. But certainly, we look at things like rainfall, turbidity, temperature—and basically, they 

almost never show a good relationship on their own with illness. And I don’t recall specifically at Surfside Beach, we were in a bit of a rush to get that report out.

Jack Colford: I’ll just add, in the next session, Vince Chow, a doctoral student at [UC] Berkeley 

is going to present a talk with data from Avalon [Beach], where Ali Boehm from Stanford 

collected a lot of these physical indicators. Vince is working on methods to incorporate those 

into the analyses.

Jiyoung Lee: We also compared water quality and E. coli and other genetic markers. We saw 

some really significant correlation, especially phosphorus and E. coli. Jason [Marion] is 

presenting a poster about that. Based on phosphorus and E. coli, can you predict tomorrow’s 

water quality? In other words, based on yesterday’s phosphorus and E. coli, can we predict 

today’s E. coli level for advisory purposes? That is another presentation. Based on our principal component analysis, we saw a significant correlation between water inflow and E. coli—

especially yesterday’s inflow. With precipitation, rainfall, and E. coli, we saw a correlation. 

For viruses, we saw the opposite. So for viruses, when there was very low inflow, we saw 

more viruses. Thus, it looks like a viruses and E. coli might have a different input transmission routes or input sources.

Question 7

Lyman Welch: I have a question about sensitive populations and I was wondering why, Dr. Fleming, 

you didn’t include children in your study? But, did you look at the elderly or pregnant women to see if 

there’s any increased sensitivity there. And then, Dr. Lee, it looked like you included children, I wasn’t 

sure if you looked at children specifically to see if there was any greater connection or sensitivity to that 

population or to other potentially sensitive populations?

Answer 7

Lora Fleming: I wish I had included children. I made a decision not to do that for two reasons; 

one issue was just logistically—we had to do a lot in a very little time. Children are a bigger 

issue for us because how would you get a child to get their own water sample? There were 

also issues of how we were logistically going to play out the study design with children. The 
143

Day Two: Session V

other issue was that our IRB [internal review board] indicated that they were going to give 

me a big hassle about it, and I needed to start the study. But having said that, I was part of 

the early [pilot study] group who said that children are probably the most important target 

group in terms of sensitivity. We took age into account and that was not an issue. I think 

there were only two or three pregnant women, and you can’t say anything about that. It’s 

just not enough statistically to look at.

Jiyoung Lee: Our sample size is so small that we don’t see a significant difference in terms of 

age.

Lora Fleming: Except that you have a lot of stuff about diapers and eating. And I’ll bet you if 

you look at the kids, the diapers, the eating, there’s a real cluster.

Jiyoung Lee: Yes, exactly. The consumption of food is really a confounder, especially in the 

children.

Question 8

Bernard Franklin: Lora [Fleming], you had indicated in your study that you saw higher incidence at 

high tide. Could you comment on potential re-growth?

Answer 8

Lora Fleming: I’ll probably punt that over to Helena [Dr. Solo-Gabriele]. And remember, it was 

higher incidence of the Enterococcus; it did not play out when we did the epi study.

Helena Solo-Gabriele: We’ve conducted some preliminary studies on that sand. And the sand 

can dry for a period, and if you re-wet it, you can increase the number. But you don’t know if 

it’s re-growth, but there is a spike in culture.

Question 9

John [unknown last name]: I’m very familiar with Tim’s [Wade’s] studies. Jack [Colford], this is for 

you. It looks like you have very much of a binary situation with the berm-open, berm-closed, and I was 

just wondering—the extent that the human contribution is, obviously, a big variable here—if there is 

any effort to characterize the discharge from that waterbody in terms of [inaudible]?

Answer 9

Jack Colford: Great question. I’m going to turn to another John, Dr. John Griffith [SCCWRP] to 

comment on some of source tracking and other sort-of parallel studies that are going on in 

concert.

John Griffith: There were several markers run. The data’s still out on some of them, although 

Jack didn’t show that data this time. Polyomavirus did pop up as significant correlation when 

the berm was open, but not when the berm was closed. When the berm was closed, we 

didn’t see anything as far as a correlation. We still have to run quite a bit of the data.

Question 10

Dianne Waters: Two questions. First, I noticed with the epidemiology, most of the reporting had demographics, it’s 95 percent white and I think another one was 92 percent white. I was wondering if there 

are any plans to account for that? I noticed one is reporting as a certain percentage as Hispanic—I 

think the one in Puerto Rico. However Hispanic is not a race, so you can’t really compare that demographic to the demographics other places and try and draw conclusions. My second question is that 

I noticed that there was an effort to take into account nonpoint sources, and most of them were over 

land. Has there been any effort to take into account stormwater runoff when it’s coming from stormwater outfall pipes?
U.S. EPA’s National Beach Conference

144

Answer 10

Tim Wade: Right, Hispanic is an ethnicity and we did clump them together because despite 

the OMB requiring us to do it, the people actually often insisted that they wouldn’t give a 

race after saying Hispanic. Since it was a very sensitive thing, we did group them like that. 

And the beach that we studied in South Carolina wasn’t typical, I may have said it was, 

but that was a mistake. I think that we had a more mixed population at some of our other 

beaches in terms of racial makeup. Our goal with the study was to reflect the beach going 

population, so whoever was there. And stormwater, I’m not sure about that. The best study 

I know that directly linked to stormwater was the Haille study that was mentioned before, 

that looked at storm drains, but I don’t think that any of our studies addressed that.

Question 10 (follow-up)

Dianne Water: Most of the studies that were considering nonpoint source pollution were only considering a swash or some sort of over-land flow. And technically stormwater is considered a point source, 

but it’s sort of a nonpoint source that gets collected in the pipe and is collected as a point source at the 

end. Were there any plans to consider whether there are different things going on when you have water 

flowing underground and discharging from a pipe that’s nonpoint source, point source pollution, rather 

than just over-land flow?

Answer 10 (follow-up)

Tim Wade: Right, we don’t have any plans for that.

Comment 10

Lora Fleming: Could I just comment on race/ethnicity too? I have similar experience in Miami 

with the fact that most Hispanics consider themselves Hispanic rather than identifying 

with a race. Also, in Miami, there is a long history of a so-called “colored beach,” where 

it was a segregated beach, it’s actually on this same island, it’s been turned into a historic 

site, but many of the black population of Miami do not swim because of that—because they 

had terrible currents and people used to drown there regularly. In terms of our study, there 

were black people in the study, but the majority are from island communities, not African 

American.

Question 11

Mark Gold: Tim [Wade], sort of a follow-up. On the Haille study, there was a pretty strong association on one particular beach in proximity to swimming next to a flowing storm drain. So this sort of 

follows up with Ali’s [Boehm’s] point too. It looked like you had that opportunity to look at that data set 

in South Carolina in that manner, because of that swash, having a flowing drain right there. Have you 

taken a look at that to see what the instance of illness is? Fifty yards, 100 yards, that kind of thing?

Answer 11

Tim Wade: Good point. We haven’t done that yet. But I definitely do see that as something 

that we could do. We have the locations of where people were in relation to where, presumably, they swam the most. We have GPS measurements of where they were, at least at the 

time of the interview. So, we haven’t done it yet, but that’s an example of something else we 

could do with the data.

Question 11 (follow-up)

Mark Gold: And one other thing on the South Carolina study is that some of these epidemiology studies, it’s amazing that when it’s announced that you’re going to move forward and do the epidemiology 

study, this sort of phenomenon of improved water quality occurs. We’ve seen it in New Jersey, we’ve 

seen it in Mission Bay, and we’ve seen it in a bunch of different places. Was there any kind of concerted effort by the community, for example, to do source abatement prior to this study? Infrastructure 

improvements, that kind of thing?
145

Day Two: Session V

Answer 11 (follow-up)

Tim Wade: It seems to happen all too commonly with epidemiology studies; if you want to 

clean up a place, do an epi study there. Sometimes I’ve actually suspected people actually 

cleaning it up. But I didn’t have any indication that anything like that was going on, not that 

I know of.

Question 12

Gil Dichter: Just to follow up on that question to the subtropical testing for the epi studies, since the 

data didn’t really show any correlation between the qPCR and illness, how are we going to use the data 

to support either certain levels for enterococci or E. coli against illness? Do we plan to do some additional studies in subtropic waters to get correlation data? This takes me back again to the 1986 study, 

where many epidemiologists disagreed with the data. Are we going to have this again?

Answer 12

Tim Wade: Probably. I don’t know if that was directed at our study; we did not see an association with the qPCR-based indicators. There were some measurement issues and how that 

plays out, I’m not sure. But I understand the point.

Question 13

Stefan Wuertz: I have a general question to all the presenters. How did you deal with nondetect data? 

I think this is probably not so important to the standard cultivation-based methods, but it certainly 

is very relevant for qPCR data, in particular pathogens, and if you then do correlations or regression 

analysis. So I just want to ask how you dealt with nondetects and whether you included detection 

limits?

Answer 13

Tim Wade: This was brought up by some in our internal peer review regularly, so we kind of 

did an exhaustive—especially with the data that’s already been published—process of various types of approaches to statistically handle it. I think that we mention in our publications 

that basically, the health relationships are really unaltered by the approaches used. Now, I 

only feel comfortable doing this when you are under the, maybe 15 percent nondetects; when 

you start getting up to 50, 60, 70 percent nondetects, I think it’s a real statistical issue that no 

one agrees on the best way to use the data. So I think there some further statistical work that 

needs to be done—especially with qPCR data, how to handle it.

Jack Colford: Yes, I think it’s an important sort of sensitivity analysis to do. And John 

[Griffith], correct me if I’m wrong, did we assign half the detection limit to the nondetects? 

But we were following in Tim’s [Wade’s] footsteps, because you had tried some maximum 

likelihood approaches.

Tim Wade: Well, we did many approaches and what we actually found was that, in terms of 

establishing a health relationship, using half was just as good as using some non-parametric 

statistics and maximum likelihood approaches, so we ended up just using half, but we had a 

sensitivity analysis that showed that we could justify it in other...

Question 13 (follow-up)

Stefan Wuertz: So you used a substitution method, which is actually usually not recommended?

Answer 13 (follow-up)

Tim Wade: It’s not recommended for describing the level, but in terms of actually developing 

association with health effects, from my understanding, it’s not as clear.
U.S. EPA’s National Beach Conference

146

Question 14

Elizabeth Halliday: My question is about the negative controls that were used in these studies. I think 

it’s really interesting that in the Miami study, you really isolated the bathers and the non-bathers; 

like the non-bathers had no interaction with the beach and a picture tells a thousand words with them 

sitting on the tarp and plastic chairs. I wonder about, especially at Doheny [Beach], whether the nonswimmers still had significant interaction with the beach and beach sands and whether you think that 

might affect the odds ratio between the swimmers and non-swimmers?

Answer 14

Jack Colford: Let me clarify: I didn’t make a big point of this in the talk, but the swimmers 

versus non-swimmer analysis obviously includes the non-swimmers. The other analyses for 

the indicators, it’s only the trend among the swimmers. It doesn’t affect it much when we use 

the non-swimmers, but they’re done separately. We didn’t see it having much of an impact 

when you include them. The field has gone back and forth on this; there have even been published papers on the use of non-swimmers in these analyses. So we’re trying to be consistent 

with what EPA has done.

Comment 14

Tim Wade: Just to add to that by using swimmers as your own control—there’s two comparisons: “versus non-swimmers” and “among swimmers;” and “among swimmers” is a bit more 

rigorous because the swimmers would also not have this recall issue, which Lora [Fleming] 

notes is still an issue in a randomized study. So, presumably, they would have the same recall 

bias as the other swimmers. Another advantage of developing relationships among swimmers 

is that they are probably effectively blind to what they’re exposed to, their level of indicator.

Comment 14 (follow-up)

Lora Fleming: Regardless of the study design?

Tim Wade: Regardless of the study design, right. I think the randomized design does give 

you a much better idea of what the non-swimmer rate is, if you can sort out the recall issue.

Lora Fleming: And the problem with the randomized design is that you effectively eliminate 

the ability to look at dose-response within the swimmers because you made them all have 

the same exposure.

Question 15

Sharon Nappier: Two quick questions for Dr. Lee. For the first one, you found associations with the 

E. coli culture in the GI, not for E. coli qPCR. I didn’t know if you could speak to the frozen filters and 

if you did some recovery analyses, and how they were stored and handled? Also, you have associations 

with adenovirus, and I didn’t know if you plan to look at norovirus specifically?

Answer 15

Jiyoung Lee: I think that kind of study has been done by other researchers. The beauty of qPCR 

is that their DNA should stay in the water. So actually, we measured E. coli using plate-based 

methods and the Enterococcus for qPCR. So the DNA should remain pretty much in the sample, 

and then the gene copies numbers are a lot in the frozen samples. So, we didn’t really do the 

decay of frozen DNA as time went by, but, based upon the literature, or other researchers, I 

think that should be okay. But, I think the freezing temperature is more significant; so rather 

than –20 °C, –80 °C is much better. So, I think that the temperature [might] affect some DNA 

decay, but the duration should be okay. We did norovirus first; that’s why I collaborated with 

Dr. Linda Safe, who is the expert. We didn’t find any norovirus. We only targeted human norovirus, and the norovirus was not there. And then also, we compared our measurement with 

the Linda Safe group, and we found similar results. We found in addition and then concentration procedure, we paralleled our study, but we found the same. So I think that our sample 

water volume was too small, so that’s why we didn’t see norovirus.