Sources of DNA contamination and decontamination procedures in the forensic laboratory

The sensitivity of forensic DNA typing techniques can cause problems when evidence samples are inadvertently contaminated with DNA from another source. Therefore, precautions need to be taken to minimize the risk of contamination. In this study, laboratory air and surfaces, tools and equipment were evaluated as potential sources of contaminating DNA. Subsequently, two decontamination procedures, i.e. the conventionally used sodium hypochlorite and the commercially available DNA decontamination solution DNA ZAPTM (Applied Biosystems), were compared for their use in removing potentially contaminating DNA from the laboratory working environment. From our results, it can be concluded that air is unlikely to be the source of observed DNA contamination in the laboratory whereas DNA accumulating on surfaces, tools and equipment within the laboratory environment may potentially be transferred to evidence samples. DNA ZAPTM outperformed the conventionally used sodium hypochlorite decontamination procedure. Stringent preventive measures and decontamination of equipment and laboratory surfaces is important to avoid secondary transfer of this contaminating DNA to evidence samples

How to use secondary data on seafood contamination for probabilistic exposure assessment purposes? Main problems and potential solutions

Seafood consumption is related to both favorable health benefits of nutrients and to potential adverse health impacts of chemical contamination. To quantify the magnitude of this dilemma, probabilistic intake assessments can be performed. One step in such a procedure involves the determination of nutrient and contaminant concentrations in seafood for which data need to be collected. This article describes the process of building up a database containing previously published contaminant concentrations in seafood, and defining input distributions characterizing the variability. During the constitution of the database, several problems influencing the comparability of the data were encountered related to (1) sampling plans of the published data; (2) sample handling prior to analysis; (3) analytical methodologies; (4) the format of reporting results; and (5) missing data. Different solutions for these methodological problems have been developed. Contaminant concentrations ranges per gram fresh weight of 2.4-4390.0 ng for mercury, 0.1-5736.6 ng for the sum of indicator PCB, 0.002-115.000 pg TEQ for the sum of all PCBs, 0.002-34.400 pg TEQ for dioxins, and 0.006-126.000 pg TEQ for total of dioxin-like compounds were found. This work confirms that more guidelines are needed to standardize the analytical methodologies to be used and the format for result reporting in order to improve the comparability of data critical to conduct a human intake and risk-benefit assessment

Uncertainty and Variability Modelling of Chemical Exposure through Food

The deterministic approach in current EU risk assessment directives, of new and existing substances deals with uncertainty as a technical construct under the format of worst-case assumptions and safety factors as if these 'certain uncertainties' can lead to certain risk estimates. In this way, the considered uncertainty and variability in the exposure and risk estimates is made insufficiently transparent which prevents policy-makers to properly assess and manage potential chemical risks. Uncertainty and probabilistic analysis is a useful process for risk assessors and managers that quantifies to the extent possible the uncertainty and variability of chemical exposure to humans through food.status: publishe