The Covid-19 pandemic has highlighted epidemiological links between climate change, environmental degradation, and increases in the frequency and severity of infectious diseases, especially Covid-19. The Pacific Basin Consortium for Environment and Health held a focus group meeting in September 2021 to discuss how environmental exposures affect the spread of infectious diseases. Covid-19 was the focus. Evidence was presented to show how poor air quality was associated with an increased prevalence and severity of Covid-19. Short-term exposures, including wildfire smoke were found to be associated with increased numbers of Covid-19 cases, while chronic exposures were more closely associated with increased severity and mortality from Covid-19. The plausibility of these associations was enhanced by reports of decreased severity and mortality seen when air quality improved during enforced lockdowns. Several potential mechanisms for these outcomes were discussed. Evidence indicates that pollution-induced oxidative stress, especially in the respiratory epithelium, was likely to be key. Laboratory studies demonstrated that pollution-associated environmentally persistent free radicals (EPFRs) disrupted epithelial homeostasis and integrity, resulting in increased replication of the SARS-CoV-2 virus and more severe consequences of epithelial infection. The potential role of oxidative stress was further highlighted by data showing the ability of a dietary antioxidant, astaxanthin, to prevent most, but not all of the EPFR-induced changes. Data were presented demonstrating how the ancestral strain of SARS-CoV-2 replicated less well than more recent strains in epithelial cells obtained from children. This appears to be related to enhanced anti-viral immune response in children’s respiratory epithelium. Most zoonotic diseases depend on complex, environmentally driven interactions between humans and animals which occur along an occupational and recreational environmental continuum including farming and animal marketing systems, environmental management systems, and community leisure environments. Changes in the environment that result from climate change, increased population density, and intensification of agriculture have been linked to increased transmission events. The growing recognition of a need for a One Health approach to combat infections is signalling to governments the need to develop policy that optimises trade-offs across human, animal, and environmental health sectors. Assessing environmental impacts on health in the Pacific Basin is challenged by significantly varying data types – quantities, qualities, and paucities – because of varying geographic sizes, environments, biodiversity, ecological assets, and human population densities, with highly varied and unequal socio-economic development and capacity to respond to environmental and health challenges. Discussion showed that while a common theme for assessing environmental impacts on health in the Pacific Basin is the availability of high quality and quantity data to support stronger policy decisions and appropriate prioritizing of investment. It is also clear that for many countries in the Pacific Basin, having sufficient data will remain a challenge to inform decision makers about environmental impact on health.