Third of tested plastic products found to leach toxic substances in Swedish study

ScienceDaily (May 16, 2011) — Many plastic products contain hazardous chemicals that can leach to the surroundings. In studies conducted at the University of Gothenburg, a third of the tested plastic products released toxic substances, including 5 out of 13 products intended for children.

"Considering how common plastic products are, how quickly the production of plastic has increased and the amount of chemicals that humans and the environment are exposed to, it is important to replace the most hazardous substances in plastic products with less hazardous alternatives," says Delilah Lithner of the Department of Plant and Environmental Sciences at the University of Gothenburg.

Plastics exist in many different chemical compositions and are widespread in the society and the environment. Global annual production of plastics has doubled over the past 15 years, to 245 million tonnes in 2008. The plastic polymers are not regarded as toxic, but there may be toxic residual chemicals, chemical additives and degradation products in the plastic products that can leach out as they are not bound to the plastic polymer. Plastics also cause many waste problems.

In her research, Lithner studied the toxicity of 83 randomly selected plastic products and synthetic textiles. The newly purchased products were leached in pure (deionised) water for 1-3 days. The acute toxicity of the water was then tested using water fleas (Daphnia magna).

"A third of all the 83 plastic products and synthetic chemicals that were tested released substances that were acutely toxic to the water fleas, despite the leaching being mild. Five out of 13 products that were intended for children were toxic, for example bath toys and buoyancy aids such as inflatable armbands," says Delilah Lithner.

The products that resulted in toxic water were soft to semi-soft products made from plasticised PVC or polyurethane, as well as epoxy products and textiles made from various plastic fibres. The toxicity was mainly caused by fat-soluble organic substances.

Lithner also studied the chemicals used to make around 50 different plastic polymers and has identified the plastic polymers for which the most hazardous chemicals are used. They were then ranked on the basis of the environmental and health hazard classifications that exist for the chemicals. Examples of plastic polymers made from the most hazardous chemicals are certain polyurethanes, polyacrylonitriles, PVC, epoxy and certain styrene copolymers. The results are of great benefit for further assessing environmental and health risks associated with plastic materials.

The thesis Environmental and health hazards of chemicals in plastic polymers and products was successfully defended in public on 6th May 2011.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Gothenburg, via EurekAlert!, a service of AAAS.

Note: If no author is given, the source is cited instead.

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Swedish invention simplifies home diagnostics

Advances in medical diagnostic technology will likely allow individuals to perform preliminary medical diagnoses themselves, in their own home, in the future.

"The idea is to make complex diagnostic processes as simple to perform as modern-day pregnancy tests," says Nathaniel Robinson, who leads the Transport and Separations Group at Linköping University in Sweden

Dr. Robinson and PhD student Per Erlandsson have invented an improved pump, called an electroosmotic pump, which can be placed in a "microfluidic chip." Such chips, sometimes called "lab-on-a-chip" devices, contain miniaturized versions of the beakers and test tubes found in chemistry laboratories interconnected by tiny pipes. Rather than using moving parts, the new pump moves fluids in these pipes via an electric current. The fluids to be pumped can be biological samples such as blood, urine or saliva for medical devices.

"The trick is to generate the ionic current that moves the fluid to be pumped without disturbing the cells, proteins, and other molecules in the sample," according to Dr. Robinson.

To do this, the researchers have employed a type of electronically conducting plastic in the pump's electrodes. The plastic can be electrochemically oxidized or reduced, acting as a transducer between the ions, the charge carriers in fluids, and electrons, which carry charge in metal wires. Traditional electroosmotic pumps use metal electrodes and the electrochemical reactions required are performed on the water in the sample itself. By-products of this electrochemistry included oxygen and hydrogen gas bubbles, and the production of acid or base. Each of these by-products disturbs the microfluidic device and the fluid sample.

"This is primarily why electroosmotic pumps have not been more widely used in the development of medical devices," says Robinson.

The researchers have shown that the pump can be operated repeatedly for extended periods of time, and can operate at relatively low voltages, so that small, portable diagnostic devices can be driven by batteries.

"Several microfluidics articles describe ways to work around the complications associated with integrated metal-electrodes. Here, the alternative reactions of electrochemically active electrodes give us the chance to remove the core problem, the electrolysis of solvent," according to Per Erlandsson, who constructed the pumps.

The researchers have applied for a patent for the new invention and are currently looking for partners who have a need for such pumps in their lab-on-a-chip devices. The research is also described in an article appearing in the latest issue of the scientific journal Electrophoresis.

Simple-to-operate medical devices, that will ultimately enable preliminary self-diagnosis via automated testing kits, will likely become an important part of our healthcare system. Otherwise, we will have a difficult time financing healthcare for an aging population at current or expanded levels of service. For example, by automating and simplifying screening for diseases, such as cancer, a greater portion of the population can be screened, more cases will be caught early, and hospital resources can focus on treatment of individuals who are truly ill. This pump is a significant step towards realizing the devices that will make this possible.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Expertanswer (Expertsvar in Swedish), via AlphaGalileo.

Journal Reference:

Per G. Erlandsson, Nathaniel D. Robinson. Electrolysis-reducing electrodes for electrokinetic devices. Electrophoresis, 2011; 32 (6-7): 784 DOI: 10.1002/elps.201000617