Butter as an indicator of regional persistent organic pollutant contamination: further development of the approach using polychlorinated dioxins and furans (PCDD/Fs), and dioxin-like polychlorinated biphenyls (PCBs). 
The potential for use of butter as a widely available, relatively uniform lipid-rich matrix for the determination of spatial distributions of persistent organic pollutants has already been demonstrated.  The present study determines the contributions to toxicity equivalence (TEQ) from polychlorinated dioxins and furans (PCDD/Fs) and polychlorinated biphenyls (PCBs) using butter samples from 24 countries world wide.  Concentrations of PCDD/Fs and dioxin-like PCBs ranged from 0.07 to 5.69 pg SigmaWHO-TEQ g(-1) lipid.  For most samples, PCDD/F TEQ fell within ranges reported for European dairy products over the last decade (0.3-2 pg x g(-1) lipid I-TEQ), though a single sample from Spain was a notable exception.  Other than this sample, the highest values were recorded for samples from the Netherlands and Italy, with those from India, China and Tunisia also being relatively high.  The contribution from non-ortho-PCBs was particularly significant in samples from Germany, Austria, Italy, the Czech Republic, Tunisia, India and Argentina.  Although overall TEQs were generally highest in European and Mediterranean butters, elevated levels were also apparent in industrializing regions of Asia (India, China) and Latin America (Argentina).  More detailed regional studies would be necessary to identify likely dioxin and PCB sources in each case.  Nevertheless, this study supports the utility of butter as a monitoring matrix that may be especially applicable in regions for which monitoring programmes are currently lacking.