Chemical composition and in vitro aryl hydrocarbon receptor-mediated activity of atmospheric particulate matter at an urban, agricultural and industrial site in North Africa (Bizerte, Tunisia)

As recognized risk factor to pose a health threat to humans and wildlife globally, atmospheric particulate matter (PM) were collected from a North African coastal city (Bizerte, Tunisia) for one year, and were characterized for their chemical compositions, including mercury (Hg_PM), as well as organic contaminants (polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs)), organic carbon (OC) and organic nitrogen (ON), determined in a previous study. Then, we applied an in vitro reporter gene assay (DR-CALUX) to detect and quantify the dioxin-like activity of PM-associated organic contaminants. Results showed that average Hg_PM concentration over the entire sampling period was found to be 13.4 ± 12 pg m^-3. Seasonal variation in the Hg_PM concentration was observed with lower values in spring and summer and higher values in winter and autumn due to the variation of meteorological conditions together with the emission sources. Principal component analysis suggested that fossil fuel combustion and a nearby cement factory were the dominant anthropogenic Hg_PM sources. Aryl hydrocarbon receptor (AhR)-mediated activities were observed in all organic extracts of atmospheric PM from Bizerte city (388.3-1543.6 fg m^-3), and shows significant positive correlations with all PM-associated organic contaminants. A significant proportion of dioxin-like activity of PM was related to PAHs. The dioxin-like activity followed the same trend as PM-associated organic contaminants, with higher dioxin-like activity in the cold season than in the warm season, indicating the advantage and utility of the use of bioassays in risk assessment of complex environmental samples.

Preliminary findings with a new Vietnamese Stroop test

Stroop performance was compared in primary Vietnamese- vs English-speaking individuals (age range 19-68 years), currently living in the USA. A modified Vietnamese Stroop task mimicked word, color, and interference effects of an English-language Stroop test. Stroop performance (items correctly completed and interference "cost") did not differ significantly between 30 Vietnamese Americans whose first language was Vietnamese (M age 34.3 yr.) vs 30 American-born individuals whose first language was English (M age 31.2 yr.). Expected performance decrements with aging were observed in English-language Stroop performance but not in Vietnamese-language Stroop performance, which instead exhibited a trend towards the opposite pattern. Unexpected group differences associated with age in Stroop performance may reflect subtle differences in task demands, not evident in simple category performance scores, or alternatively, cultural or neuropsychological differences in the study groups.