The association of air pollution with adverse cardiopulmonary health outcomes may be underestimated because of misclassification errors introduced by uncertainty in the exposure assessment of aerosols. Until recently, the excessive cost of high-end aerosol measurement devices (>$10,000) has prevented the regular collection of aerosol data with high spatial and temporal resolution with exposure measurements often being limited to a single site to represent large populations. In some cases, new, low-cost (<$500) aerosol devices have been found to correlate favorably to high-cost devices. However, these low-cost devices suffer from some limitations, such as an inability to distinguish between fine and coarse particles. The proposed study aims to overcome these limitations by designing and evaluating a customized, aerosol sensor based on low-cost, high-resolution cameras. The low-cost sensor will enable routine aerosol assessment among the general population, providing estimates of aerosol concentrations resolved by size (fine and coarse aerosol) and time (<5 min logging).