1795

Background:Ultrafine particles (UFP) are emitted by both jet engine aircraft and road traffic and may potentially confound associations between noise and health outcomes. However, neither UFP or noise are routinely measured resulting in a lack of understanding of their relationship. Methods: We conducted repeated short-term measurements with portable sensors (noise - Cirrus Research Optimus sound level meter (CR:171B); PNC - TSI 3007 condensation particle counter) to assess the correlation between noise and UFP number concentrations (PNC) for aircraft and road traffic. Noise and PNC were measured contemporaneously for 30-minutes at 160 sites (repeated three times at a range of site types) in Norwich, a medium size city in the east of England, and repeatedly up to 71 times per site at nine sites (501 in total) around Gatwick airport. Results:In Combining all measurements at Gatwick Airport the correlation between noise and PNC was very weak (ρ = 0.11). Strongest correlations were moderate (|>0.4-0.6|) at a residential site 1.3 km north of the runway and a site 0.6 km south of the runway. The correlation between noise and PNC in Norwich was overall moderate (ρ = 0.52) and weak (ρ <0.4) for roadside sites (n = 55) and urban background sites (n = 90) respectively. Conclusion: Results suggest that PNC are unlikely to be a major confounder in epidemiological studies of aircraft or road noise and cardiovascular disease.