Aliphatic Polycarbonates from Cyclic Carbonate Monomers and Their Application as Biomaterials.

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.

Living in a sea of lead--changes in blood- and hand-lead of infants living near a smelter.

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 microg/dl began a slow linear increase until 14-18 months where a plateau occurred of 10.8-17.2 microg/dl. The blood-lead levels were well correlated with hand-lead loadings of infant (r(2)=0.72, P<0.01, log transformed data) and mother (r(2)=0.62, P<0.01, log transformed data) unless the birth lead level was exceptionally high. The principle factor determining exposure was the 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 microg/dl per microg/day with a maximum daily dose of 3-5 microg/kg/day, assuming 45% absorption. Ingestion appears to be the most likely route for at least 95% of the dose.

Incidence, impact on the family and cost of gastroenteritis among 4 to 6-year-old children in South Australia.

BACKGROUND: Gastroenteritis is an important cause of morbidity in both adults and children worldwide. Although the burden of morbidity and mortality is highest in developing countries, gastroenteritis is still a significant cause of morbidity in Australia, particularly in young children. The aims of the present study were to determine the incidence of gastroenteritis among 4-6-year-old children in South Australia, to describe the impact on daily activities of the child and caregiver and estimate the cost of gastroenteritis in this population. METHODS: A diary study of drinking water consumption and gastrointestinal and respiratory symptoms was undertaken among 965 rural children in South Australia over a 6-week period during February-May 1999. Data on the response to gastrointestinal episodes were collected by telephone surveys midway and at the end of the 6-week period. Costing was based on the methods of Hellard et al. RESULTS: The incidence of community gastroenteritis among 4-6-year-old children was 5.53 episodes per child-year (95% confidence interval: 4.87-5.80). The costs associated with childhood gastroenteritis were estimated to be between 16,858,360 AU dollars and 22,477,814 AU dollars per annum. CONCLUSIONS: The incidence of community gastroenteritis among the 4-6-year-olds in the South Australian population is high and it costs the community a significant amount of money in terms of direct medical costs and time lost by parents and carers looking after their ill children.

An evaluation of recent blood lead levels in Port Pirie, South Australia.

The Port Pirie Lead Program commenced in 1984. The abatement program involves identification of children with elevated blood lead levels, house decontamination, soil treatment, development of heavily vegetated buffer zones around the smelter, family education and support and community education. Since 1984 the smelter has also implemented substantial new emission controls and environmental improvements. Blood lead and air monitoring programs as well as investigations of emission sources, ongoing household contamination and infant exposure mechanisms are in place. Although capillary blood lead monitoring has shown a significant decrease in the mean blood lead levels of the children, 61% of children aged 1-4 years still exceed 10 microg/dl, with 28% at or above 15 microg/dl. Re-entrainment of lead from the contaminated areas within the city is only a small contributor to air-borne lead levels compared with that from the smelter and its environs. The smelter has undertaken extensive work to reduce windborne fugitive emissions. While attempts to demonstrate reductions in air lead have been hampered by large annual variations in wind speed and direction, air lead studies have confirmed that only small losses are now arising from the stockpile area of the smelter site. Evidence suggests that worker hygiene improvements, relocation of children to lower exposure suburbs, community education, house decontamination, specific measures for individual children with elevated blood lead, and avoidance of tank rainwater have all been partially successful. A substantial investigation program has refocused intervention efforts towards reducing exposure from indoor environments during the first year of life and contributed to improved identification and ranking of ongoing smelter emission sources.