The city of Baia Mare is located in the Baia Mare Depression, a region which is characterized by intense anthropogenic activity. Due to the long-lasting local mining and metallurgical tradition, this area was among the most problematic in the country in terms of historical pollution and its consequences. In Baia Mare, pollution is chronic (historical), but also diversified, with several notable sources. The present paper, the first part of a complex three-piece study, aims to provide an overview of the historical sources of air pollution in Baia Mare, while the second part will highlight the air quality evolution in Baia Mare between 1995 and 2006, and the third and final piece will analyse the effects of this chronic pollution on human health. This article is a historical, descriptive and analytical investigation of the main sources of historical environmental pollution (including air pollution) in Baia Mare. The aim of the study is to highlight the activities carried out by these polluting companies and to emphasize the contribution of these activities and various technological processes to air pollution in Baia Mare, between 1995 and 2006. The industry in Maramures County, where Baia Mare is located, had a significant contribution to the country’s lead, copper, gold and silver production. At the same time, due to the nature of their activities, these industrial branches were heavy polluters. The historical environmental pollution (including air pollution) in Baia Mare had three major sources: the National Company of Precious and Nonferrous Metals (NCPNM) - Remin Corporation; Cuprom Corporation; Romplumb Corporation. NCPNM - Remin Corporation processed polymetallic deposits of lead, zinc, copper and ferro-manganese deposits, and the company was an important producer of gold, silver, lead, zinc and copper concentrates. The basic activity of Cuprom Corporation consisted of extracting nonferrous metals by pyrometallurgically processing cuprous and gold concentrates. The main activity performed by Romplumb Corporation was obtaining decopperised lead by pyrometallurgically processing lead-cuprous concentrates. The activities of the three major companies led to the systematic exceedances of limit values set for the pollutants resulting from various technological processes, namely suspended particulate matter, heavy metals and SO 2 . All three companies were active for decades and, until the early 2000s, environmental protection was not a priority in the technological process management of these three metallurgical centres. Unfortunately, after the year 2000, investments in green technologies were insufficient and, starting with 2008, the economic crisis also affected the three companies mentioned above. Currently, NCPNM - Remin and Romplumb Corporations are insolvent and Cuprom Corporation is bankrupt.