Coal burning factories and increased automobile usage has caused the most significant increase in which of these:

respiratory illnesses

nuclear waste

soil depletion

water pollution

The most significant increase caused by coal burning factories and increased automobile usage is likely water pollution. These activities release pollutants into the air, which eventually find their way into water bodies such as rivers, lakes, and oceans. This water pollution can have detrimental effects on aquatic ecosystems and also pose health risks to humans and animals who rely on these water sources for drinking or recreation.