Effect of drug precursors and chemicals relevant to clandestine laboratory investigation on plastic bags used for collection and storage

- Degradation process of evidence plastic bags and interactions between chemicals and polymers is presented.
- Comparison of different plastic bags (PVC and LDPE) currently used by Police was undertaken.
- Damages to evidence bags occur with extreme conditions such as UV exposure and humidity.
- Results demonstrated better resistance of LDPE bags compared to PVC bags.
- Recommendations are given regarding the storing of chemicals directly into evidence plastic bags.

In the area of clandestine laboratory investigations, plastic bags are used to collect and store evidence, such as solvents, precursors, and other compounds usually employed for the manufacturing of drugs (although liquids may be stored in glass containers within the bags first). In this study, three different types of plastic bags were provided by the NSW Police Force and investigated for their suitability for evidence collection: two different types of low-density polyethylene (LDPE) bags and one type of polyvinyl chloride (PVC) bag. Three different experiments were carried out: (1) storing relevant chemicals in the bags for up to three months; (2) exposing the bags including their content to accelerated conditions using a weatherometer, and (3) simulating an expected real case scenario. This study indicates that drugs and related chemicals stored in plastic bags may lead to a change in the composition of the chemical and an alteration or degradation of the plastic bag. All experiments led to the same conclusion: the polyvinyl chloride bags appeared to be the most affected. LDPE bags seem to be more appropriate for routine use, although it has been established they are not suitable for the collection of liquids (unless pre-packaged in, for instance, a glass container).