Background/Aim: Air pollution is a major cause of cardiovascular and all-cause morbidity and mortality. However, disentangling the relative contributions of individual pollutants is challenging, as epidemiological data measuring exposure to one (e.g. nitrogen dioxide; NO2) is inevitably confounded by exposure to others (e.g. particulate matter). Domestic gas appliances, e.g. cookers, represent a globally important, yet under-recognized, source of NO2 and provide a relatively selective method to investigate the effects of NO2. We hypothesized that acute exposure to NO2 from gas cooking would lower blood pressure (BP) by increasing plasma [nitrite]. Methods: We conducted an acute, randomized, controlled, crossover study to assess the impact of 90min exposure to NO2 versus control (room air) on plasma [nitrite] and BP in healthy volunteers.Results: Plasma [nitrite] was significantly elevated compared to control over the 3-hour period comprising 90min NO2 exposure and 90min washout (P<0.001), notably within 15min of exposure (P<0.05), and at all timepoints until 2h15min (45min after the end of exposure); P<0.05. There were corresponding decreases in systolic and diastolic BP over the 3-hour period (both P<0.001). Systolic BP was decreased relative to control at individual timepoints of 45min and 90min by 4.6mmHg (95% CI 0.2 to 8.9; P=0.032) and 5.5mmHg (95% CI 1.2 to 9.9; P=0.005), respectively. The maximal diastolic BP difference was 5.7mmHg (95% CI 1.0 to 10.5; P=0.009) at 45min.Conclusions: NO2 exposure from gas cooking acutely lowers BP, associated with a rapid increase (by 15min) in plasma [nitrite]. This finding favours chemical conversion via intermediates over induction of inflammatory pathways. Such a functional "ecophysiological NOx cycle" may directly feed into the "nitrate-nitrite-NO pathway", thus linking with wider evidence on both beneficial and adverse cardiovascular effects. Our proposed mechanism contributes to the understanding of how NO2 exposure impacts human health.