Aliphatic polycarbonates have gained increased attention as biomaterials largely owing to their biocompatibility and tunable degradation. Moreover, the ability to introduce functional handles in the polymer backbone through careful design of cyclic carbonate monomers or copolymerization with other biodegradable polymers has significantly contributed to the interest in exploiting this class of materials for biomedical applications. Such investigations have enabled their utility to be expanded to a wide variety of applications in the biomedical field, from drug delivery to tissue regeneration and the design of vascular grafts. Herein, we review the synthesis, degradation, and studies into biomedical applications of aliphatic polycarbonates obtained by ring-opening polymerization of cyclic carbonate monomers (ring sizes between 6 and 8). While all synthetic methods will be covered, particular emphasis will be given to materials that have been exploited for therapeutic applications in vitro and in vivo.

Gastroenteritis was found to be a significant cause of morbidity among young children. Young children, who were regular consumers of tank rainwater, were at no greater odds of gastroenteritis than those who drank treated public mains water.

Thirteen infants born into the lead contaminated environment of Port Pirie, South Australia, were followed approximately monthly from birth until they were about 36 months. Blood-lead levels of infants at birth were similar to their mothers but fell rapidly during the first 35 days of life. Thereafter, infants born with blood-lead levels at about 2-4 mg/dl began a slow linear increase until 14-18 months where a plateau occurred of 10.8-17.2 mg/dl. The bloodlead levels were well correlated with hand-lead loadings of infant (r 2 ¼ 0.72, Po0.01, log transformed data) and mother (r 2 ¼ 0.62, Po0.01, log transformed data) unless the birth lead level was exceptionally high. The principle factor determining exposure was thee impact of smelter emissions on the house. Blood-lead increase was caused by the relatively more rapid increase in dose of lead compared with the increasing body mass, which was related directly to the maturation of motor development. Hand-lead of mothers were closely related to both infants' blood-and hand-lead levels until the point of blood-lead plateau then substantially fell as infants began to walk unaided. The estimated slope factor using the ICRP model was 0.75-0.94 mg/dl per mg/ day with a maximum daily dose of 3-5 mg/kg/day, assuming 45% absorption. Ingestion appears to be the most likely route for at least 95% of the dose.

Despite an extensive cleanup program in the Port Pirie region, South Australia, the levels of lead (Pb) in blood of children have been found to exceed the "level of concern" (10 µg/dL). The ingestion of household dust is a major pathway for elevated blood lead by children in the community. Significant differences in levels of Pb in blood in children were observed in various localities around the smelter. In this study an in vitro test was assessed as one method for determining the bioavailability of Pb in household dust and for predicting levels of Pb in blood of children. The solubility of Pb in the dust decreased significantly as pH of the in vitro mixture increased. Correlation studies with average blood Pb levels of children in the corresponding area and in vitro measures of Pb bioavailability found that the best relationship was with total dust Pb (r 2 ) 0.92, **). A significant positive relationship was also found with Pb concentrations determined in the in vitro test at pH 3.0 (r 2 ) 0.82, **). This suggested that for these dust samples, which all had a similar environmental matrix, the use of the in vitro test was not a better indicator of blood Pb levels in children compared with a total Pb analysis.

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