The People's Republic of China, the world's most populous nation, is considering extensive development of its automotive transportation infrastructure. Upper limits to the associated pollution increases can be defined through scenarios with Western style vehicles and vehicle-to-person ratios. Here we construct estimates of fundamental changes to chemistry of the Pacific ocean/atmosphere system through simple budgeting procedures. Regional increases in tropospheric ozone could reach tens of parts per billion. Observations/experiments suggest that enhanced nitrogen oxides will react with sea salt aerosols to yield chlorine atoms in the marine boundary layer. Nitrate deposition onto the open sea surface would support several percent of exported North Pacific carbon production. Transport of biologically active iron to surface waters may follow from increases in mineral dust and acid sulfate aerosols. Altered plankton ecodynamics will feed back into climate processes through sea to air flux of reduced sulfur gases and through carbon dioxide drawdown.¿ 1997 American Geophysical Union