He had been working at the Swiss Federal Institute of Aquatic Science and Technology (Eawag), where he was the head of the division Chemische Problemstoffe.
Giger is a pioneer who advanced the field of trace organic analysis and its application to significant environmental problems.
In 1984, he discovered that in wastewater treatment plants nonylphenol ethoxylates are transformed to 4-nonylphenols, which are toxic to aquatic life.
In the meantime, he was visiting scientist at the Stanford University and lecturer at the Universität Karlsruhe.
[5] In September 2008, the journal Environmental Science & Technology dedicated a special issue to him.