What innovation is known as a significant contributor to outdoor pollution?

Burning gasoline in leaf blowers is identified as a significant contributor to outdoor pollution primarily because these machines emit harmful pollutants directly into the environment. Leaf blowers powered by gasoline tend to release a variety of emissions including particulate matter, volatile organic compounds (VOCs), and carbon monoxide. These emissions can lead to poor air quality and can have detrimental effects on respiratory health, contributing to smog and other forms of atmospheric pollution.

In contrast, hybrid cars and electric scooters are designed to reduce emissions compared to traditional gasoline-powered vehicles, thus minimizing their impact on air quality. Solar panels, being a clean energy source, do not emit pollutants during their operation. This highlights why burning gasoline in leaf blowers stands out as a major source of outdoor pollution among the options provided.