Which pollutant source contributes the least to oil spills?

The contribution of various sources to oil spills can vary significantly, and in this context, natural seepage is recognized as a significant source that occurs without human intervention. Oil tankers are often highlighted due to high-profile spills from maritime accidents, making them a substantial contributor to oil pollution.

However, when considering the least contributing source among the options presented, cities and towns generate minimal oil spill events compared to the large operations related to oil drilling and tankers. Activities related to urban settings primarily lead to stormwater runoff that may carry small amounts of oil but do not typically result in large-scale spills like those associated with tankers or drilling operations. Thus, cities and towns inherently contribute less to the cumulative totals of oil spills.

In contrast, both oil drilling operations and oil tankers are designed for the extraction and transportation of oil, hence they frequently lead to significant oil spills when accidents occur or due to operational leaks. Thus, this puts cities and towns in a position of lower contribution, emphasizing that while they can contribute oil to waterways, their impact is significantly less than that of the other selected sources.