Large variations in fluoride concentrations exist in natural waters, many of which are the source of community drinking-water supplies. Determining fluoride concentrations in community drinking waters can be challenging in developing Pacific countries such as Vanuatu that have limited laboratory capacity. Knowledge of naturally elevated fluoride concentrations that cause irreversible, adverse health outcomes may allow communities the opportunity to treat and manage their drinking-water supplies. Community drinking-water samples (n = 69), sourced from groundwaters, roof catchment rainwaters, surface waters and springs, were sampled on Tanna Island, Vanuatu between 2017 and 2020. In an 18 km2 area of Western Tanna, a set of 30 groundwater-based drinking-water samples had a median fluoride concentration of 3.3 mg/L, with 20 samples >1.5 mg/L and seven samples >4.0 mg/L. These concentrations increase the risk of dental and skeletal fluorosis, respectively. Repeat resampling at five sites showed little variation over the sampling period. Rainwater-fed drinking-water supplies were lower overall and highly variable in fluoride concentrations (<0.05–4.0 mg/L, median of 0.53 mg/L), with variable inputs from volcanic emissions from Yasur volcano. We recommend a comprehensive oral health and bone health study for the whole island to determine adverse health effects of excess fluoride in this vulnerable population.

Vanuatu is a small island state ranked the most at-risk for natural hazards globally. Access to safe and secure water is limited, particularly for poor and rural residents. It is projected that climate change will increase temperatures, sea level, cyclone intensity, and extreme rainfall events in Vanuatu. As the impacts of climate change become clearer, it is becoming easier to predict the consequences of those changes on water infrastructure. The Government of Vanuatu, Department of Water Resources (DoWR) wants to support communities to enhance the resilience of community water supply infrastructure, despite the additional challenge of climate change. Since 2013, DoWR has adapted Water Safety Plans to the local context with Drinking Water Safety and Security Plans (DWSSPs). An analysis of actions taken after 199 DWSSPs, site visits and interviews, revealed an opportunity to integrate climate change more into existing community risk planning processes. The analysis also identified many potential problems with existing water infrastructure that increase their exposure to climate risks as well as possible improvements to decrease those risks. As a result, adjustments were made to the current water safety planning approach, so that communities review hazards associated with climate change and identify resilient infrastructure improvements.

In Small Island Developing States (SIDS), water pollution is not monitored or assessed frequently enough to fully understand the processes, impacts of water quality issues and what solutions are available This study investigated flushing time in Erakor lagoon and Port Vila Bay, Vanuatu using a numerical model developed in Delft3D. Microbial contamination by Escherichia coli was detected in multiple locations in the lagoon system with counts exceeding thresholds related to human health concerns. Modelling demonstrated a poor flushing time overall with a further decrease as the influence of waves and wind increased, especially in Vila Bay. Sea level rise resulted in an increase in flushing time downstream of the lagoon near the open sea, while with a decrease upstream and in Vila Bay. Based on these results, we recommend long-term continuous monitoring and identification of higher risks areas to prioritise decisions around wastewater management.

Rainwater collection and storage is critical to water security in Vanuatu and the wider Pacific region. Across all Pacific Islands countries (PICs), more than one in six households-or around 2 million people-rely on rainwater collection as their main drinking water source (Table 1). Rainwater collection systems are especially important in Vanuatu, serving as the main source of drinking water for 36% of households (VNSO, 2017).Rainwater collection as a source of drinking water presents potential advantages and disadvantages, which in turn have important implications for efforts to achieve the Sustainable Development Goal (SDG) of safe water for all in Vanuatu and the wider Pacific region. The headline indicator linked to SDG target 6.1 requires safely managed water services to be improved source types, accessible on the premises, free of fecal and priority chemical contamination, and available in sufficient quantities when needed. Rainwater at the time of capture is typically of good quality and is defined as an inherently "improved" water source by the WHO/UNICEF Joint Monitoring Programme (WHO/UNICEF, 2018). However, there is clear evidence that rainwater collection systems in Vanuatu are still prone to fecal contamination , while others have noted concerns in regards to physical and chemical contaminants (Allibone et al., 2012;Kotra et al., 2017). Rainwater collection systems are often owned and managed by private households, and hence are commonly located on the premises of users. This reduces water collection times and minimizes the need for storing water in the household, which otherwise presents a contamination risk (Shields et al., 2015).Perhaps the most significant weakness of rainwater collection systems is their ability to ensure water is available in sufficient quantities when needed. These systems are highly vulnerable to climatic conditions,

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