The conventional approach to evaluating the impact of air pollution is to focus on a single exposure during a fixed period of time. But evidence suggests that contaminants work together, magnifying the damage to people's lungs. Conventional studies fail to probe synergistic effects. They also ignore the cumulative effects of lifelong exposures to pollutants, known as the exposome. Researchers need to shift away from single-pollutant studies and towards those involving a broad range of exposures.