Recent investigations have found that organic chemicals may contaminate drinking water by permeating buried plastic pipes and gasket materials. Pipe-bottle direct-exposure experiments and microbalance experiments were conducted in order to determine the susceptibility of polybutylene (PB) piping material and gasket materials to permeation by a wide range of organic chemicals. Many lipophilic compounds tested were found to permeate to a detectable level in consumers' tap water within a month at one third of their aqueous solubilities. It was also found that PB was more permeable than low-density polyethylene to toluene and that chlorinated hydrocarbons permeated PB faster than unchlorinated hydrocarbons. Gasoline compositions such as benzene, toluene, ethyl benzene, and xylenes appeared to be highly permeable to PB and gasket material. The organic chemicals were approximately 5 to 100 times more permeable in gasket materials than in PB.The development of plastic extrusion years. The polymers commonly used for technology has led to the extensive use these purposes have been polyvinyl of plastic water conduits and pipe gaskets chloride (PVC), polyethylene (PE), polyin the potable water industry in recent butylene (PB), and acrylonitrile-butadi-ene-styrene (ASS) for water pipe and tubing and styrene-butadiene-rubber (SBR) for the push-on type of pipe gasket used to connect PVC, ductile iron, steel, or concrete water pipes. SBR is used in more than 90 percent ofthe applications.' Other types of polymers such as Neoprene (chlorinated rubbers), ethylenepropylene-diene-monomer (EPDM), nitrile rubbers, and fluorinated rubbers are also used in the manufacture of pipe gaskets. These materials are immune to corrosion, easy to install, ductile, durable, and energy efficient to manufacture. They are not, however, impervious to many organic chemicals, which allows contamination of the potable water.

Polybutylene pipes (0.75 in.) buried in both water‐saturated and unsaturated soils contaminated with toluene, trichloroethylene, 1,2‐dichlorobenzene, and o‐chlorophenol were permeated to detectable levels in 1 to 150 days, depending on the organic chemical and its concentration. Comparison of these results with pipe‐bottle experiments containing no soil showed that the concentration of organic chemical in the soil pore controls the rate of organic chemical permeation through buried plastic pipes. The results also indicate that under otherwise identical conditions, plastic pipes buried in a soil of high organic carbon content will be permeated more slowly than pipe buried in a soil of low organic carbon content. Even so, soils of very high organic carbon content cannot be relied on to protect plastic pipe from permeation by organic chemicals. A method for predicting the equilibrium concentration of organic chemical in the soil pore was useful in determining whether a plastic pipe buried in contaminated soil is likely to be permeated.

SYNOPSISThe permeation parameters, partition coefficient and diffusion coefficient, were obtained for polybutylene (PB) with toluene using a gravimetric method. A PB sample was repeatedly exposed and desorbed, and the partition coefficient and diffusion coefficient were measured. Permeation parameters were also measured at different temperatures. The results were compared with those obtained from a 12-year-old PB pipe sample, which had experienced structural failure. Tests at an elevated temperature of 45°C failed to simulate the effect of polymer aging, whereas repeated sorption/desorption tests produced permeation parameters compatible with those of a 12-year-old PB pipe in service. I NTRODU CTlO NThe major thermoplastic materials used for potable water transport and plumbing applications include poly ( vinyl chloride) ( PVC ) , chlorinated poly ( vinyl chloride) (CPVC) , polyethylene ( P E ) , polybutylene ( PB ) , and acrylonitrile-butadiene-styrene ( ABS ) .Advantages claimed for plastic pipes include immunity to corrosion, ease of use, ductility, and durability. During the last decade, however, it has been found that plastic piping and gasket materials are susceptible to attack and/or permeation by certain organic chemicals.'s2Polymers are permeated by organic chemicals through a combination of partitioning (solubility) and diffusion phenomena. Prediction of a partition coefficient and diffusion coefficient has been attempted by other ~esearchers.~'~ For aromatic organic chemicals, the vapor-phase partition coefficient was predicted from a logarithmic correlation with the saturation vapor concentration for PB and styrene butadiene rubber (SBR) .' Also, the diffusion coefficient was estimated from the relationship between the molecular diameter and the logarithm of the diffusion coefficient for PVC, PB, and SBR.' During service, polymers may change their physical properties including strength, stiffness, strain at failure, and permeability. Attempts have been made to evaluate the changes of original properties over a long period of time. One method adopted by EPA is to raise the temperature to 5OoC to test chemical ~ompatibilities.~ It is not clear whether a test at an elevated temperature can produce permeation parameters comparable to those of samples exposed to organic chemicals for a long time. A technique should be developed to assess the effects the aging of a polymer has on its permeability. In other words, how does the performance of a polymer change when it is exposed to organic chemicals for a long service time.The objective of this paper is to evaluate permeability of PB to toluene after long-term use. The results from 12-year-old specimens, repeated sorption-desorption tests, and various temperature conditions are compared. MATERIALS AND METHODS MaterialsPB, trade name for poly ( 1-butene) , is a member of the polyolefin group of polymers made of straightchain hydrocarbons. PB is partially crystalline and 2989

SYNOPSISThe amount of solute sorbed per unit weight of sorbent, qe, and the equilibrium solubility (partition) coefficient were measured using a gravimetric method for various types of organic chemicals in thermoplastics and elastomers. A thermodynamic model was derived to predict the activity-dependent partition coefficient and qe for a wide range of organic chemicals. The thermodynamic model produced a better fit to the measured qe values than did the Flory-Huggins equation. Partition coefficients and qe increased with increase in activity. For nonpolar compounds, qe increased logarithmically but decreased for polar compounds with an increase in the saturation organic chemical vapor concentration. Elastomers had 14-28 times greater qe values than did thermoplastics. A structure-activity relationship was found to accurately predict the partition coefficient for liphophilic organic chemicals at a specific activity.

Scenarios are a well-established methodology used in foresight. In this paper a three-phased process is described to maximise relevance for policy-making of a set of scenarios. As a first step, four scenarios were developed as a basis for the assessment of the ability of the EU's legislative and policy framework on food safety and nutrition to deal with possible future challenges. In the second step the scenarios were analysed by stakeholders to identify the scenario-specific challenge profiles in terms of food safety and nutrition. Policy and regulatory responses were formulated towards improving the fitness of the EU food framework for the future. The pertinence and realism of this exercise generated questions about how the role of the EU policy maker in this area could develop. To answer this question, in a third step, a new tailor-made approach was developed, allowing exploring and testing policy-making under diverse circumstances. The serious gaming platform, the Joint Research Centre's Scenario Exploration System, was adapted and applied with a number of selected stakeholders. Both approaches, each on their own, demonstrated the power of scenarios for simulating realistic policy circumstances. In combination, the process allowed to examine, in systemic way, different aspects of future policies and fostering a more forward-looking mind-set to inform practical policy-making.