[en] Full text: Organic halogens, especially organochlorinated compounds, which come from extensive use of pesticides and herbicides, and discharge of wastewater from bleaching of pulp and wastewater treatment, have caused world-wide contamination and drawn great concern. Polychlorinated biphenyls, hexachlorobenzene, organochlorinated pesticides and their metaborites are well-known pollutants in the environment because of their persistence, bioaccumulation and potential environmental hazardous effect. Recently, a significant number of studies indicated that traditional analytical methods such as gas chromatography and gas chromatography- mass spectrometry could only provide information about the known organochlorines, which contributed to less than 1-20 % of total amount of extractable organochlorinated compounds in samples and therefore the results couldn't reflect their actual contamination levels. Instrumental neutron activation analysis is the only analytical method currently available for simultaneously determining various extractable organohalogens. In this work an INAA method combined with organic solvent extraction for determination of extractable organohalogens (EOX) in milk and pine needle collected from various regions of China has been established. The detection limits are 50 ng, 8 ng and 3.5 ng for Cl, Br and I, respectively. The concentrations of EOX in the samples are decreasing in the order of EOCl >> EOBr > EOI. The average concentration of EOCl in milk is 4.44 μg/g expressed as fat weight basis, with the highest 17.6 μg/g on fat weight basis from the developed regions in China. The mean concentrations of total HCH and DDT are 0.038 μg/g and 0.046 μg/g, respectively. Organochlorine pesticides only account for 1.6% of the EOCl, indicating the very high proportion of the unknown EOCl in the milk samples. The concentrations of EOCl, EOBr and EOI in pine needles are 0.5-6.0, 0.06-0.54 and 0.013- 0.4 μg/g dry weight, respectively. 5 to 38 % of EOCl exist as extractable persistent organochlorines (EPOCl) after treatment with concentrated sulfuric acid. It is observed that the average concentrations of EPOCl noticeably increase from south to north China. The relative proportion of the known organochlorinated pesticides to total EPOCl is 3.0-19.8 %, which also indicates that a major portion of EPOCl in pine needles is unknown. Further, a positive correlation of the organohalogen levels in milk and pine needle with the local social economic index was also found. (author)