Guidelines for understanding and managing risks in recreational waters: Beach sand management and best practices

On this page

• Introduction
• Microorganisms in beach sand
• Effects of beach sand on microbiological water quality
• Relationship between beach sand and human illness
• Beach management best practices

Introduction

Management of beach sand is important as 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 (DeFlorio-Barker et al., 2018). Beach sands can contain many types of microorganisms, including various human pathogens, deposited through numerous routes. This includes direct deposition of fecal materials from bird or animal droppings, human activities on beach sands, runoff from surrounding areas including from storm drains or combined sewer overflows, as well as from the adjacent waters. The concentrations of microorganisms in beach sand can be significantly greater than the adjacent water, but are highly variable over very small distances. Some studies have shown that contact with beach sand can increase the risk of GI illness (Heaney et al., 2009, 2012). Therefore, it is important for users to understand how to minimize this risk (for example, washing hands before consuming food).

Some international organizations have recently included recommendations on how to assess the microbiological quality of sand in their guidelines. For example, WHO published updated guidelines for coastal and fresh waters which includes a recommended provisional guideline value for beach sand of 60 cfu of intestinal enterococci per gram of sand (WHO, 2021). This provisional value depends on a significant assumption: that the ratios and uptake of enterococci and human pathogens are the same for water and sand. The purpose of the provisional value is to help determine whether beach sand is in need of improved management actions to reduce the concentration of fecal indicator microorganisms.

This document does not include a guideline value for beach sand as further research is needed to characterize the relationships between fecal indicator bacteria in sand and the potential implications to human health. Instead, protection of public health from beach sand risks should focus on management measures (for example, beach grooming and cleaning, access restrictions), along with education and communication. Responsible authorities may choose to include sampling beach sands for fecal indicators as a management measure. Information on sampling sands can be found in the guideline technical document on Microbiological Sampling and Analysis (Health Canada, in publication). Certain circumstances may warrant testing of sand and sediment samples, such as during investigations of potential waterborne disease outbreaks, after sewage spills or when conducting an environmental health and safety survey (see Environmental health and safety survey).

Microorganisms in beach sand

Beach sand can harbour microorganisms from fecal matter and other environmental sources. Gulls in particular are thought to be a significant source of fecal indicator bacteria for some beaches (Levesque et al., 1993; Fogarty et al., 2003; Williamson et al., 2004). Their contribution of human pathogenic microorganisms, however, is generally low but does vary depending on contamination sources in the surrounding environment where gulls may also occur (for example, wastewater management facilities) (Quessy and Messier, 1992; Lu et al., 2011; Alm et al., 2018). Canada geese populations can also present a source of fecal material at areas adjacent to surface waters, and their feces have been found to contain and transport pathogenic viruses, protozoa and bacteria that may pose a human health risk (Moriarty et al., 2011; Gorham and Lee, 2016). Non-fecal sources can include microorganisms naturally found in the sand environment as well as those deposited on the sand through mechanisms such as land runoff and wave action. The numerous sources of microorganisms that may impact beach sands can lead to high concentrations of microbes in the sand, many of which will not be a concern to human health.

Beach sands can provide more favourable conditions for survival of microorganisms than adjacent waters. They can provide 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 (Whitman and Nevers, 2003; Whitman et al., 2014). When microorganisms are introduced to the beach environment, several outcomes are possible: they may die off within hours, they may persist for days to months without replicating or some proportion of the bacterial members can become established and start growing in the environment.

The fecal indicators, E. coli and enterococci, have both exhibited a greater persistence in beach sands relative to natural waters. They have been isolated from numerous locations in the beach environment, including foreshore sands (that is, the sand directly influenced by lake water, usually between the low and high water mark), nearshore waters (Alm et al., 2003; Whitman and Nevers, 2003; Edge and Hill, 2007; Yamahara et al., 2007, 2012; Staley et al., 2016) and backshore sands (Byappanahalli et al., 2006), as well as from 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 beach wrack (Whitman et al., 2003; Ishii et al., 2006b). Both E. coli and enterococci may also replicate in beach sands under favourable conditions (Ishii et al., 2006a; Hartz et al., 2008; Yamahara et al., 2009; Halliday and Gast, 2011; Byappanahalli et al., 2012; Whitman et al., 2014). They have also been shown to reach concentrations that are many fold higher than the adjacent swimming waters (Alm et al., 2003; Whitman and Nevers, 2003; Williamson et al., 2004; Bonilla et al., 2007; Edge and Hill, 2007; Halliday and Gast, 2011). Of the beach areas studied, foreshore sands generally have the highest levels of fecal indicator bacteria, potentially resulting from the favourable survival conditions provided by the moist sand or from deposition of fecal droppings by shorebirds (Whitman and Nevers, 2003; Whitman et al., 2006; Whitman et al., 2014; Staley et al., 2016). This is the area where children tend to play in the sand. Although concentrations in beach sand can be significantly greater than the adjacent water, the concentrations are highly variable over very small distances, making beach sand monitoring difficult.

Beach sand can be a reservoir for pathogenic microorganisms that may be a risk to human health. Fecal and non-fecal pathogenic species of bacteria, viruses, parasites and fungi have been isolated from the sand environment (WHO, 2021; Shah et al., 2011). This includes Aeromonas spp., Campylobacter spp., pathogenic E. coli, Pseudomonas aeruginosa, Salmonella spp., Staphylococcus aureus, Vibrio spp., Cryptosporidium spp., Giardia spp., numerous fungal pathogens and some viral pathogens (Whitman et al., 2014). Of the pathogens studied, Salmonella spp. and Campylobacter spp. are among the most frequently detected (Bolton et al., 1999; Obiri-Danso and Jones, 1999, 2000; Yamahara et al., 2012), with the source most often being related to contamination of the beach sand by bird feces. These pathogens are not expected to grow in beach sand but can survive for various lengths of time (Eichmiller et al., 2014). S. aureus and P. aeruginosa have also been detected in some studies (Mohammed et al., 2012; Thapaliya et al., 2017). Humans are the primary source of S. aureus as it is not considered a natural inhabitant of environmental waters, whereas P. aeruginosa is widely distributed in the aquatic environment. Both of these non-enteric pathogens may survive and replicate in beach sands (Mohammed et al., 2012). Pathogenic protozoa (Abdelzaher et al., 2010; Shah et al., 2011), enteroviruses (Shah et al., 2011), and other infectious viruses, including the influenza A virus (Poulson et al., 2017), have also been isolated from sands in various marine beaches, but a plausible pathway to human infection is probably limited to the enteric viruses. Multiple pathogenic fungal species have also been identified in sand samples at marine beaches (Sabino et al., 2011).

To date, there has been no consistent relationship between the concentrations of fecal indicator microorganisms and the occurrence of pathogens in beach sands (Whitman et al., 2014).

Effects of beach sand on microbiological water quality

There have been numerous studies showing that beach sand can present a significant non-point source of fecal indicator bacteria for swimming waters (Alm et al., 2003; Whitman and Nevers, 2003; Williamson et al., 2004; Yamahara et al., 2007; Edge and Hill, 2007; Heaney et al., 2014; Torres-Bejarano et al., 2018). Disturbances to foreshore and nearshore sands and sediments can affect the microbial quality of shallow waters (WHO, 2003; Skalbeck et al., 2010; Vogel et al., 2017). These disturbances can resuspend fecal indicator microorganisms, inflating microbiological counts. Edge and Hill (2007) applied microbial source tracking techniques and found that sand could be a source of E. coli out to 150 m off a beach in Hamilton Harbour. Mechanisms of transfer of sandborne contamination to the water environment include wave swash, sand erosion, rain-mediated runoff and direct transfer from swimmers (Boehm et al., 2004; Vogel et al., 2016). A study examining the movement of enterococci through sand showed that these microorganisms were not strongly bound to beach sand and can be easily transferred to the water environment (Yamahara et al., 2007). 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- and tide-driven recirculation of water through the beach aquifer may also present a mechanism for transfer of microorganisms and nutrients from the sand environment to swimming waters. The potential health risks that may be associated with resuspension of microorganisms from beach sand is not currently known.

Relationship between beach sand and human illness

Several studies have been undertaken to determine whether exposure to beach sand (digging in sand, buried in sand) increases the risk of becoming ill. Whitman et al. (2009) looked at the transferability of E. coli and F+ coliphages from beach sand to hands to assess whether sufficient quantities of microorganisms could be transferred to make it a possible route of exposure to pathogens. They determined that if beach sands contain high levels of human pathogens, the quantities of microorganisms transferred on the fingertips and hands from playing in the sand could be sufficient to increase the risk of GI illness. This study also reaffirmed that hand washing is effective at removing these microorganisms (that is, 92% to 98% reduction), supporting the recommendation to always wash your hands before consuming food.

Heaney et al. (2009) studied associations between sand exposure and illness at marine and freshwater beaches under the U.S. EPA's National Epidemiological and Environmental Assessment of Recreational (NEEAR) Water study. The authors observed that digging in sand was associated with a modest increase in the risk of GI illness (1.13; CI = 1.02–1.25) and diarrhea (1.20; CI = 1.05–1.36). Individuals who reported being buried in sand showed a slightly higher incidence of GI illness (1.23; CI = 1.05–1.43) and diarrhea (1.24; CI = 1.01–1.52), with children under 10 years old having the strongest association. The increased risks for sand exposure were found for both swimmers and non-swimmers. No associations were demonstrated for sand contact and non-enteric illness (Heaney et al., 2009). In a follow-up study at 2 recreational marine beaches, Heaney et al. (2012) determined that individuals who reported digging in sand, where enterococci concentrations were in the highest tertile (that is, the highest third of the ordered distribution; >324 CCE/g of sand), had increased risks of GI illness (2.0: CI = 1.2–3.2) and diarrhea (2.4; CI = 1.4–4.2). Estimates were even higher for GI illness (3.3; CI = 1.3–7.9) and diarrhea (4.9; CI = 1.8–13) among individuals buried in sand. However, the study had very few participants who reported sand exposure but did not swim, so the risk from swimming could not be separated from the risk from beach sand. An earlier study by Marino et al. (1995) reported no evidence of a relationship between the incidence of skin symptoms and sand concentrations of any of the indicator organisms monitored (E. coli, fecal streptococci, Candida albicans, dermatophytic fungi) during a prospective epidemiological study at 2 beaches in Malaga, Spain. Using a QMRA approach, Shibata and Solo-Gabriele (2012) calculated the concentration of pathogens (Cryptosporidium, enteroviruses, S. aureus) in beach sand that would represent an equivalent level of risk to U.S. EPA water quality recreational limits. They determined that at a non-point source recreational beach in Florida, the concentration of pathogens in the beach sand generally presented a low infection risk.

Further research is needed to more fully characterize the relationships between fecal indicator bacteria and the possible presence of fecal pathogens in beach sand, as well as the potential implications to human health.

Beach management best practices

Combining management actions, procedures and tools into beach best management practices can collectively reduce the risks in beach sands and recreational waters, thereby protecting the health of recreational water users. Enteric pathogens are of significant concern in recreational environments, and implementing barriers to reduce the extent of fecal contamination is therefore recommended. An environmental health and safety survey is an important tool for helping recreational water operators identify potential onshore sources of fecal contamination that are relevant to their beach area (see Environmental health and safety survey). Removal of litter that may attract animals to the area and the installation of physical barriers (for example, animal-proof refuse containers, fences and gull nets) designed to discourage wildlife may be useful strategies. Restricting access of pets to public beaches during the operating season is another potential control mechanism as pets can be a significant source of fecal contamination in recreational areas.

Physical manipulation of the sand environment may also help minimize fecal contamination and reduce its transport to swimming waters (Kinzelman et al., 2004; Kinzelman and McLellan, 2009; Hernandez et al., 2014; Whitman et al., 2014; Kelly et al., 2018; Edge et al., 2018). This could include deep mechanical grooming to remove harmful materials, beach berm construction to prevent stormwater runoff onto a beach and targeted beach grading to increase the steepness of the slope, which reduces the area vulnerable to wave swash and permits more rapid sand drying through improved drainage.

Some beaches may also implement pre-emptive beach postings or swimming advisories restricting recreational water activities for short periods immediately after rainfall events. These limit swimmer exposures to fecal contamination that may have been washed into the swimming or beach area. Not all beaches are negatively impacted by rainfall events, so beach managers should determine whether pre-emptive beach postings will be beneficial for the recreational area. The decision to use pre-emptive beach postings should be based on historical monitoring results and the EHSS. Larger-scale management options for beaches require a comprehensive review of the contamination inputs and watershed characteristics and the identification of specific options to minimize or control the sources of fecal contamination and to reduce the transfer of pollution to the swimming area.

Beach users can also do their part by properly disposing of their litter, refraining from feeding animals on or near the beach, using available facilities for hygiene practices (for example, washing hands, changing diapers) and complying with any existing beach regulations or codes of conduct. They may also contribute by becoming informed of, and following, steps that can be taken to reduce their personal exposure (see Public awareness and communication).

Authorities may wish to consult the following types of resources for further information to help them address specific beach-related issues:

• Published texts: Texts are available that provide comprehensive discussion of broader topics like stormwater management, wastewater treatment and coastal water management. Texts are also available for specific topics such as differentiating plants (like duckweed) from cyanobacteria.
• Searchable databases of published articles: Keyword searches can direct the user to specific scientific studies, related articles, bibliographical citations and topic review papers. Peer-reviewed publications are preferred to information published in non-refereed sources.
• Proceedings from international conferences: A review of proceedings can identify accounts of actions evaluated in other communities, providing an indication of results and potential contacts. Specific conferences include the Great Lakes Beach Association Conferences and the U.S. EPA National Beach Conferences.
• Manuals or publications produced by stakeholder organizations.

Water quality issues can have impacts across multiple fields (for example, health, environment, agriculture, municipal infrastructure) and require an approach (for example, One Health approach) which aims to balance and optimize the health of people, animals and ecosystems by mobilizing multiple sectors, disciplines and communities to tackle threats to health and ecosystems (OHHLEP, 2021). Consultation with responsible authorities, other beach operators or service providers and recreational water quality professionals may help to identify actions that have proven to be successful in other communities.