The Port of Long Beach has cut diesel particulates by 81% since 2005, according to newly released analysis.

The results for 2012 mark six straight years of improving air quality in the harbor area due to efforts to reduce air pollution caused by goods movement.

The reasons for air quality improvements include bigger ships carrying cargo more efficiently, newer ships with cleaner engines, the Jan. 1, 2012 deadline for full implementation of the Clean Trucks Program, increasing use of shore power, and a new low-sulfur fuel rule for ships that started in August 2012.

The U.S. Environmental Protection Agency, the California Air Resources Board and the South Coast Air Quality Management District reviewed the study’s results.

Compared to 2005 emissions levels, all of the key air pollutants from port-related sources were reduced in 2012. In addition to the drop in diesel emissions, smog-forming nitrogen oxides and sulfur oxides have been cut 54% and 88%, respectively. Greenhouse gases were lowered by 24%. The reduction in pollutants far outpaced a 10% decline in containerized cargo activity in the same period.