In general, seaports are located in urban areas or in their environs, whereby their activity has a very direct effect on the population. Therefore, reducing environmental contamination and improving air quality are priority management goals for port authorities (PAs). In Spain, the state-owned seaport system consists of 28 PAs that manage 46 ports. Its regulation received a major impulse through the enactment of the Spanish Ports Law in 2010. The law establishes especially the obligation that, annually, the PA prepare a sustainability report with 111 sustainability indicators. This study is founded on a database that was created with information from the reports from 2011 to 2016. A statistical analysis studies the evolution of the implementation of 20 measures for the reduction of atmospheric contamination in Spanish ports and identify the strategic lines carried out by the PAs and the measures adopted depending on the size of the ports.