Page 14: Guidelines for Canadian Recreational Water Quality – Third Edition
Part II: Guideline Technical Documentation
This section provides information on the issue of faecal contamination and faecal indicator bacteria in beach sand, including the effects on recreational waters and steps that can be taken to reduce swimmer exposures to contamination in the sand environment.
Currently, there is no conclusive evidence of a relationship between contact with beach sand and illness among recreational water users, and no guideline values can be established for concentrations of the recommended indicators for recreational waters for faecal contamination in beach sand. Routine monitoring of sand samples for the presence of faecal indicators would not be considered practical and is thus not recommended. Certain circumstances may warrant testing of sand and sediment samples, such as during investigations of potential waterborne disease outbreaks or when conducting an Environmental Health and Safety Survey.
Further research is needed to more fully characterize the relationships between faecal indicator bacteria and the possible presence of faecal pathogens in beach sand, as well as the potential implications to human health. Combining actions, procedures and tools to collectively reduce the risk of swimmer exposure to faecal contamination in beach sand and recreational waters represents the most effective approach to protecting the health of recreational water users.
Microorganisms are a recognized natural component of beach sand, with numerous species of bacteria, viruses, parasites and fungi all having been isolated from the sand environment (WHO, 2003a). The results of recently published studies demonstrating that faecal indicator bacteria can be isolated in high numbers from foreshore and nearshore beach sand and sediments (Alm et al., 2003; Whitman and Nevers, 2003; Edge and Hill, 2007) have prompted renewed interest in the question whether sand can serve as a vehicle for the transmission of pathogenic microorganisms to beach users. Understandably, this issue is one of increasing concern to beach operators, public health officials and the beach-going public. Beach users often spend more time on the beach than in the water, and children routinely play in the sand at the water's edge.
Occurrence of faecal indicator bacteria in beach sand
Enteric bacteria are not expected to survive well once displaced from their primary habitat (the intestinal tract of humans and animals) to a secondary habitat such as the aquatic environment (Winfield and Groisman, 2003; Anderson et al., 2005). Their survival in this environment is influenced by a complex array of biological and environmental factors. Selective pressures that can have a negative effect on the survival of microorganisms in recreational waters include sunlight; osmotic stress; large variations in temperature, pH and salinity; low nutrient availability; and competition and predation by other microorganisms (Winfield and Groisman, 2003).
Beach sand and similar environments (foreshore and nearshore soils and sediments) can provide more favourable conditions for survival of microorganisms than the adjacent waters. Whitman and Nevers (2003) suggested that beach sand provides a suboptimal, yet viable, environment for the survival of enteric bacteria by providing protection from sunlight, buffered temperatures, a degree of cover from predation, large surface areas for biofilm development and a replenishing supply of moisture and organic nutrients from wave swash.
Numerous authors have observed the presence of faecal indicator bacteria in beach sands and sediments, often at concentrations several orders of magnitude higher than those of the adjacent swimming waters. At a Lake Michigan beach, Whitman and Nevers (2003) detected E. coli counts in foreshore and submerged sand (1000-10 000 mean cfu/100 mL) that exceeded those of the swimming water (100-1000 mean cfu/100 mL). Similar findings were reported by Williamson et al. (2004) in a survey of E. coli densities in swimming water and sand pore water at Lake Winnipeg beaches. Alm et al. (2003) reported that, on average, concentrations of E. coli and enterococci were 3-17 times and 4-38 times greater, respectively, than in the water column at beaches located on Lake Huron and the St. Clair River. Edge and Hill (2007) found E. coli concentrations as high as 114 000 cfu/g dry sand at a Lake Ontario beach.
Similar studies have shown that faecal indicator bacteria can be isolated from other habitats within a beach watershed, such as backshore sand (Byappanahalli et al., 2006), subtropical and temperate stream sediments (Byappanahalli et al., 2003; Jamieson et al., 2003, 2004; Ferguson et al., 2005; Ishii et al., 2006a), temperate forest soils (Byappanahalli et al., 2006) and within mats of the green algal species Cladophora (Whitman et al., 2003; Ishii et al., 2006b).
A concept that is receiving increasing attention within the scientific community is that enteric bacteria may be capable of multiplying in the sand and similar environments in tropical and subtropical climates provided that the proper conditions for growth are met (Davies et al., 1995; Byappanhalli and Fujioka, 1998; Solo-Gabrielle et al., 2000; Desmarais et al., 2002; Anderson et al., 2005). These would include (among other factors) suitable conditions of temperature, moisture and available nutrients, as well as reduced competition from other microflora. Warmer temperatures and higher soil nutrient concentrations have been cited as factors that may favour the multiplication of indicator bacteria in tropical soils (Hardina and Fujioka, 1991; Whitman and Nevers, 2003). Whitman and Nevers (2003) proposed that certain conditions that exist at tropical beaches may be encountered at temperate beaches in the United States during the summer months.
During an investigation of sand and water quality at a Lake Michigan beach, Whitman and Nevers (2003) observed that in freshly replaced beach sand E. coli was able to recolonize to earlier levels within a period of 2 weeks. The authors were not able to confirm whether the effect was due to multiplication in an unexploited environment or the result of deposition by external sources. Kinzelman et al. (2004a) detected similar levels of diversity among E. coli strains collected from water, foreshore sands and submerged sands at a Racine, Wisconsin, beach. It was suggested that accumulation, and not replication, was the major contributor to E. coli observed in the sand.
A few researchers have suggested that some portion of the sand- or soilborne strains of E. coli may represent a genetically distinct group, separate from the majority of isolates that dominate in the host sources (Winfield and Groisman, 2003; Byappanahalli et al., 2006; Edge and Hill, 2007). Moreover, it is proposed that these strains may have adapted for prolonged survival and possibly growth in the soil environment (Winfield and Groisman, 2003; Byappanahalli et al., 2006). Byappanahalli et al. (2006) reported finding evidence of a genetically diverse E. coli population among forest soils located within a Lake Michigan watershed. Ishii et al. (2006a) reported finding evidence of "naturalized" E. coli populations in northern temperate soils located within Lake Superior watersheds. The authors further reported that these strains were capable of multiplying in non-amended, non-sterile soils at temperatures at or above 30°C.
Effects of beach sand on microbiological water quality
There has been a wealth of information in support of the notion that beach sand can present a significant non-point source of faecal contamination for swimming waters (Alm et al., 2003; Whitman and Nevers, 2003; Williamson et al., 2004). Faecal indicator bacteria in sand can originate from a variety of faecal pollution sources. Gulls in particular are thought to be a significant source of faecal contamination for beaches (Levesque et al., 1993; Fogarty et al., 2003; Williamson et al., 2004). Canada geese populations can also present a source of faecal contamination at areas adjacent to surface waters (Alderisio and DeLuca, 1999).
Mechanisms of transfer of sandborne contamination to the water environment include wave swash, rain-mediated runoff and direct transfer from swimmers. Resuspension of nearshore sediments can occur through a number of mechanisms, including wave action (including those artificially generated by commercial and recreational boating), storms and swimmer activities. Boehm et al. (2004) proposed that the wave-driven and tidally driven recirculation of water through the beach aquifier may also present a mechanism for transfer of microorganisms and nutrients from the sand environment to swimming waters.
Pathogenic microorganisms in beach sand
Few studies have been published regarding the occurrence and survival of enteric pathogens in beach sand and sediments. Bolton et al. (1999) reported that culturable Campylobacter and Salmonella species were detected in 45% and 6% of sand samples, respectively, in beach sand samples collected from various UK coastal beaches. Obiri-Danso and Jones (1999) reported that Campylobacter could be detected year-round in low numbers (< 0.5 log cfu/g dry weight) in river sediments at two freshwater swimming sites in the northwest of England. Salmonella was not detected at either site. In a follow-up study at coastal beaches within the same watershed, Obiri-Danso and Jones (2000) detected Campylobacter (C. lari, urease-positive thermophilic campylobacters) in sediment samples collected during the winter months only. C. jejuni and C. coli could not be isolated, and Salmonella was not detected at any point during the analysis. The authors concluded that the sediments were not acting as a reservoir for these pathogens in this system. NWRI (2006) found Campylobacter species commonly occurring in sand pore water at two bird-contaminated beaches in Hamilton Harbour, Lake Ontario. C. jejuni were more common than C. coli or C. lari, although all species appeared to be in low numbers in the pore water.
Others have reported the detection of S. aureus and P. aeruginosa in beach sand (Papadakis et al., 1997; Esiobu et al., 2004). P. aeruginosa is a relatively hardy species of bacteria that is widely distributed in the aquatic environment and is known to cause skin rashes and eye and ear infections in swimmers. Humans are the primary source of S. aureus in recreational waters; thus, its presence in beach sand is thought to be directly related to swimmer activities. The organism is known to be associated with skin infections in swimmers (rashes, infected cuts and scratches). Very few data are available regarding the presence of other potential recreational waterborne pathogens (viruses, protozoan parasites) in beach sand (WHO, 2003a).
Despite the findings that faecal indicator bacteria and potentially pathogenic microorganisms can be detected in beach sand, there has been little evidence published to indicate a link to illness among beach users. Marino et al. (1995) reported that there was no evidence of a relationship between the incidence of skin symptoms and sand concentrations of any of the indicator organisms monitored (E. coli, faecal streptococci, Candida albicans, dermatophytic fungi) during a prospective epidemiological study at two beaches in Malaga, Spain. Heaney et al. (2009) studied associations between sand exposure and illness at marine and freshwater beaches under the U.S. EPA's NEEAR study. The rates of illness varied from beach to beach, however, overall the authors observed that digging in sand was associated with a modest increase in reported gastrointestinal illness (adjusted incidence ratio 1.13; 95% confidence interval [CI] 1.02-125). Individuals who reported being buried in sand showed a slightly stronger incidence of gastrointestinal illness (1.23; CI,1.05-1.43) and diarrhea (1.24; CI,1.01-1.52). No associations were demonstrated for sand contact and non-enteric illness (Heaney et al., 2009). Epidemiological studies in which microbiological sampling has been performed at very shallow depths have similarly failed to show a correlation between water quality at this depth and swimmer illness (Calderon et al., 1991; Fleisher et al., 1996; McBride et al., 1998; Haile et al., 1999). Microbiological counts in shallower waters can be expected to exceed those at greater depths, owing to disturbances to foreshore and nearshore sands and sediments.
Managing health risks
Management actions to reduce the extent of faecal contamination affecting the beach area, as well as steps to restrict swimmer exposure to recreational waters during periods of or in areas perceived to be at increased risk are part of an effective strategy to protect against the risk of human exposure to pathogens arising from faecal contamination in the foreshore and nearshore sand environment.
The Environmental Health and Safety Survey is an important tool for helping recreational water operators identify potential onshore sources of faecal contamination that are relevant to their beach area. Further information on the EHSS process can be found in Part I (Management of Recreational Waters).
For beach managers and operators, barriers to reduce the extent of faecal contamination can include the physical removal of litter that may attract animals to the area and the installation of physical barriers designed to discourage wildlife. Examples of such barriers can include animal-proof refuse containers, fences and gull nets. Jurisdictional regulations restricting access for pets on public beaches present another potential control mechanism.
Physical manipulations of the sand environment have also been proposed as a potential action to help minimize faecal contamination and reduce its transport to swimming waters. Kinzelman et al. (2004b) reported that deep mechanical grooming without levelling was effective in reducing sand levels of E. coli at a Racine, Wisconsin, beach, particularly in wet sand. Targeted beach grading to increase the steepness of the slope of a beach has been suggested as another action that can improve water quality (City of Racine Health Department, 2006). A more steeply sloped beach reduces the area vulnerable to wave swash and permits more rapid sand drying through improved drainage (Clean Beaches Council, 2005; City of Racine Health Department, 2006).
Pre-emptive beach postings or swimming advisories restricting recreational water activities for short periods immediately after rainfall events present another potential barrier. These act by limiting swimmer exposure to faecal contamination that may have been washed from the sand environment to the swimming area.
Beach users can also do their part to contribute to these strategies by ensuring that their litter is properly disposed of, refraining from feeding animals on or near the beach, and complying with any existing beach regulations or codes of conduct. They may also contribute by becoming informed of steps that can be taken to reduce their personal exposure. Beach users are reminded to adopt proper hygiene practices such as avoiding mouth contact with items that have been in contact with sand, washing their hands prior to eating and showering as soon as is practical after visits to the beach. The use of clean beach towels can also help reduce the degree of sand contact (WHO, 2003a).
Larger-scale management options for beaches will require a comprehensive review of the contamination inputs and watershed characteristics and the identification of specific options to minimize or control the sources of faecal contamination and to reduce the transfer of pollution to the swimming area.
- Beach sand and related environments may provide a more favourable environment for microorganisms of faecal origin, which may permit them to survive for longer periods than in the adjacent water. Physical factors such as wave action, storm surges, tidal activity and high swimmer load can result in the transference of microorganisms from foreshore and nearshore sand and sediments to swimming waters.
- Currently, there is no conclusive evidence to indicate a link between microorganisms in beach sand and illness among beach users. Further research is needed to determine the relationships between faecal indicator bacteria and the possible presence of faecal pathogens in beach sand, as well as the potential implications to human health.
- Barriers that collectively reduce risk of exposure for beach users could include public education campaigns, improved beach sanitation practices, appropriate sand grooming practices and actions designed to discourage the activities of animals (birds and other wildlife) within the beach area.
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