Located in northern Portugal, the municipality of Estarreja is the study area for this OHM.I. It derives its originality of the presence of the second largest complex chemical country mainly producing ammonium sulphate, nitric acid and ammonium nitrate, but also synthetic resins (PVC), and its location near the largest brackish water lagoon of Portugal, the Ria of Aveiro.
Subjected to intense industrial pollution since the early 1950s, this area has suffered the simultaneous effects of solid waste, liquid and gas in the environment, which have both affected some plant and animal organisms and raised questions about health local populations.