1. Emissions are waste from production, distribution and consumption, which are distributed to environmental media. Emmision is often restricted to pollutants.
2. Emissions generally means discharge of any interference in the environment. The source is called the issuer. Each emission causes an immission.
http://www.dictionary.com/browse/emission (1.); https://www.bfga.de/arbeitsschutz-lexikon-von-a-bis-z/fachbegriffe-c-i/emission/ (2.)