This paper investigates the relationship between illnesses commonly associated with swimming, and faecal indicator bacteria as determined by qPCR methods, by comparing estimates of faecal indicators with incidences of illness. The study took place at three marine beaches, located in Mississippi, Rhode Island and Alabama, USA. Each of the beaches is sited within 7 miles of a treated sewage discharge outfall, and although water quality varies at each, they all comply with water quality guidelines. The beach in Mississippi was sampled in 2005 whereas the other two beaches were sampled in 2007.
Water samples were collected in waist-high and shin-high water from three transects, which included the swimming area. Environmental conditions were also recorded at the time of sampling, as well as information relating to use of the beach (numbers of people and animals etc.). The samples were tested for total Enterococcus spp. and total Bacteroidales spp. by qPCR, and samples taken in 2007 were also tested for subgroups of Bacteroides and Clostridium spp. Samples from 2007 were also tested for F+ coliphage using two methods; a culture and latex agglutination (CLAT) assay, and a culture-based EPA method.
Visitors to the beach on sampling days were asked to participate in the study. Eligible participants were asked to complete questionnaires regarding contact with water and sand, and ten to twelve days later a telephone interview was conducted to determine whether gastro-intestinal (GI), skin, respiratory, eye or ear problems had occurred following their visit. 6350 visitors participated.
The occurrence of GI illness was associated with an increase in exposure to estimates of Enterococcus spp. and Bacteroidales spp. When highest levels of Bacteroidales were present, 12% of swimmers reported illness compared to 6% of non-swimmers. Positive relationships were found between incidences of GI illness and estimates of subgroups of Bacteroides and Clostridium spp., and estimates of F+ coliphages, but these were not statistically significant.
The study is the first to find a relationship between incidences of GI illness and estimates of faecal indicator organisms, as estimated using qPCR, at marine beaches. The findings suggest that qPCR methods give a good indication of poor water quality and the effects on the health of visitors. They also support the need for more rapid testing of bathing waters.
A review of: 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’, Environmental Health, 9:66.
4 comments:
Hi Helen,
Just a quick question - do the authors give any indication of what the water quality regulations are over in the USA? Are they simalar to what we have here? It would be interesting to know.
Rachel
Hi Rachel
The authors do mention that 104 cfu/100ml Enterococcus is the EPA (Environmental Protection Agency) recommended single sample maximum for marine beaches.
But looking at this document from the EPA it seems a bit more complicated than that, as it looks like different regions have adopted different standards:
http://water.epa.gov/type/oceb/beaches/upload/2003_06_19_beaches_local_statrept.pdf
It says that they recommend maximum densities of faecal coliforms do not exceed 200 organisms per 100ml.
Hi Rachel,
I really enjoyed your review, an interesting paper and conclusions.
In reference to the study -
Was the level of interaction between the water and a beach user described in the study? - such as a definition characterising the difference between a swimmer and a non-swimmer? Also, were any details given regarding individuals who may have been repeatedly using the beach within the sampling time and how/if they were accounted for?
These considerations may not have been directly neccessary in achieving the aims of this study in determining a relationship between health issues and water quality, but perhaps should be considered in a wider approach to measuring and maintaining marine bathing water quality.
Hi David,
Swimming was defined as "body immersion" ie immersion to the waist or higher, whereas non-swimmers had no contact with water. The authors reported that they had previously observed similar risks of illness between people who immerse their body and those that immerse their head.
The authors stated that frequency of visits to the beach was a covariate which could affect the relationship between water quality and illness, but they found that excluding those who had swimming contact in the previous week did not really affect the results for associations between GI illness and numbers of Enterococcus and Bacteroidales.
I would agree with your comment that consideration should be given to these issues.
Post a Comment