Anthropogenic and natural environmental contaminants are a common problem and a source of concern to ecosystem health. Industrial toxins are one of the leading causes of pollution worldwide. Industrial toxins may arise as a result of air emissions, water releases, water seepage, air deposition or disposal and leaching of solid waste. The combination of natural and anthropogenic sources of toxins present challenges with respect to the protection of local ecological environments. Predicting the impacts of environmental contaminants on ecosystems become an important part of the decision-making process for managing environment problems. To protect ecological environments and species, it is necessary to assess the risk to organisms exposed to toxins, and find relevant factors that determine the persistence and extirpation of populations. Over the past several decades, ecotoxicological models have been widely applied to predict contaminant effects.

Inhaled particles are readily phagocytosed by alveolar macrophages (AMs) present in the lung. Other routes of particle exposure targeting the lung and frequently used with animal models include intratracheal instillation and oropharyngeal aspiration. The mechanism (s) by which AMs drive pulmonary toxicity downstream of particle uptake is not fully understood, as well as the contributing role of other phagocytic cell types present in the airways and lung including epithelial cells.

In this study, the effects of the Polycyclic Aromatic Hydrocarbon (PAH) Benzo (α) pyrene (BαP) exposure on the levels of serotonin (5-HT) and dopamine (DA) in the pituitary and hypothalamus of Yellowfin seabream, (Acanthopagrus latus) were examined. To assess the acute stress responses, vegetable oil (2 µl g-1) containing BαP (50 mg kg-1) was injected into the treatment group of fish (the vegetable oil alone was the control), and brain samples from different groups were collected 3 hr after injection. Base line group was not injected. To study the long-term stress, brains were collected from both injected groups after 72 hr. The amounts of serotonin, dopamine, and amine metabolites in the hypothalamus and pituitary were measured. Results showed that BαP influenced the serotonergic system more than the dopaminergic system for both acute and prolonged stress in both the hypothalamus and pituitary. Acute exposure to BαP induced significant decreases in DA and increases in DOPAC (3, 4-dihydroxyphenylacetic acid) in the pituitary (P<0.05). Major changes induced by both acute and prolonged exposure to BαP included significant decreases in 5-HT, increases in 5-HIAA (5-hydroxy-3- indoleacetic acid) and increases in the 5-HIAA/5-HT ratio (P<0.05). These exposures might affect the synthesis, storage, uptake/release, and degradation of the neurotransmitters in the hypothalamus and pituitary of sea bream, especially the pituitary gland.