同体儿童血、发铅浓度及同位素比值研究

目的探讨儿童血、发铅同位素比值的指纹特征,为寻找人体可蓄积性铅源做数据积累。方法随机抽取北京城市和农村儿童各14名,男女各半,用ICP-MS测定其血样及发样的铅浓度及同位素比值。结果城市和农村儿童的血铅同位素比值不同,而发铅同位素比值则无显著性差异;发铅同位素比值与血铅同位素比值有显著性差异,即同体血、发铅指纹存在差异现象。结论北京市城乡两地的血铅污染程度近似,但铅源不完全相同;人体不同组织器官对不同铅同位素可能具有选择性蓄积。     

Use of rapid needs assessment as a tool to identify vaccination delays in Guatemala and Peru

ObjectiveTo explore the use of rapid needs assessment (RNA) surveys to determine the prevalence and factors contributing to delays in vaccination of children in two low middle-income countries (LMIC).MethodsData from two RNA surveys performed as part of program improvement evaluations in Guatemala and Peru were used for this analysis. The primary endpoint was the timeliness of immunization with delay defined as administration of vaccines beyond 28 days from recommended age for DTwP-HepB-Hib (Penta) and measles–mumps–rubella (MMR) vaccines, as well as past age-restrictions for rotavirus vaccine. Independent risk factors analyzed included child's gender, birth year, number of children in household, maternal age, maternal education, and food insecurity.ResultsVaccine information was available from 811 children from 838 households surveyed. High rate of immunization delays was observed, with 75.6% of children in Guatemala and 57.8% of children in Peru being delayed for the third dose of Penta primary series. Factors associated with delayed vaccination in Guatemala included advanced maternal age and increased number of children in household. In Peru, significant associations were birth year before 2009, lower maternal education level, and increased number of children in household.ConclusionsRNA is a fast and effective method to identify timely vaccine coverage and derive a hypothesis of factors possibly associated with vaccination delay.     

Clinical lead poisoning in England: an analysis of routine sources of data

OBJECTIVE: To examine the occurrence of clinical lead poisoning in England based on routine sources of data. METHODS: Three routine data sources were examined, over different periods according to availability of data: (a) mortality for England, 1981-96; (b) hospital episode statistics data for England, for the 3 years 1 April 1992-31 March 1995; (c) statutory returns to the Health and Safety Executive under the reporting of injuries, diseases, and dangerous occurrences regulations (RIDDOR), also for the period 1 April 1992-31 March 1995. Also, analyses of blood lead concentrations carried out by the Medical Toxicology Unit, Guy's and St Thomas' Hospital Trust in London during the period 1 January 1991-31 December 1997 were examined. The analyses were performed both for industrial screening purposes and in response to clinicians' requests where lead poisoning was suspected. This is one of several laboratories carrying out such analyses in the United Kingdom. RESULTS: One death, of a 2 year old girl, was coded to lead poisoning in England during 1981-96. Analysis of hospital episode statistics data identified 83 hospital cases (124 admissions) over 3 years with any mention of lead poisoning, excluding two with admissions dating from 1965 and 1969. For these 83 cases the median hospital stay per admission was 3 days (range 0-115 days). Five were coded as having received intravenous treatment. Further clinical details of these cases beyond what is routinely recorded on the hospital episode statistics database were not available, except for blood lead concentrations in cases also identified on the Medical Toxicology Unit database. Eighteen cases (22%) were below 5 years of age of whom 10 (56%) came from the most deprived quintile of electoral wards. There was evidence to suggest spatial clustering of cases (p = 0.02). Six occupational cases were reported under RIDDOR in England during the period of study, two of whom were identified on the hospital episode statistics database. One further occupational case was identified on hospital episode statistics. Blood lead analyses for 4424 people carried out by the Medical Toxicology Unit (estimated at about 5% of such analyses in England over 7 years) found that among 547 children aged 0-4, 45 (8.2%) had a blood lead concentration in excess of 25 micrograms/dl, the action level in the United Kingdom for investigation, or removal of environmental sources of lead. At all ages, there were 419 (9.5%) such people, including 106 adults with no mention of industrial exposure. CONCLUSIONS: Both mortality and hospital admission ascribed to lead poisoning in England are rare, but cases continue to occur and some, at least, seem to be associated with considerable morbidity. Lead poisoning was confirmed as a probable cause of clinical signs and symptoms in only a small proportion of those in whom a blood lead concentration was requested. Where indicated, appropriate remedial action for the safe removal of environmental sources of lead should be taken.

 

     

Genetic susceptibility to lead poisoning

Major strides have been taken in the regulation of lead intoxication in the general population, but studies using genetic markers of susceptibility to environmental toxicants raise the question of whether genes can make certain individuals more vulnerable to environmental toxins such as lead. At least three polymorphic genes have been identified that potentially can influence the bioaccumulation and toxicokinetics of lead in humans. The first gene to be discussed in this review is the gene coding for delta-aminolevulinic acid dehydratase (ALAD), an enzyme of heme biosynthesis, that exists in two polymorphic forms. The resulting isozymes have been shown to affect the blood and bone lead levels in human populations. The effects of ALAD in lead intoxication have also been studied in laboratory mice that differ in the genetic dose for this enzyme. The second gene reviewed here is the vitamin D receptor (VDR) gene. The VDR is involved in calcium absorption through the gut and into calcium-rich tissues such as bone. Recent findings suggest that VDR polymorphism may influence the accumulation of lead in bone. Finally, the third gene to be discussed here that may influence the absorption of lead is the hemochromatosis gene coding for the HFE protein. The presence of mutations in the HFE gene leads to hemochromatosis in homozygotic individuals. Because of the associations between iron and lead transport, it is possible that polymorphisms in the HFE gene may also influence the absorption of lead, but this has not yet been studied. More studies will be needed to define the role of these genes in lead intoxication.     

铅毒性的遗传易感性

环境铅污染对儿童健康的影响正日益受到重视。以往的流行病学研究发现 ,机体的易感性可能是铅毒性作用的重要决定因素。δ 氨基 γ 酮戊酸脱水酶基因、维生素D受体基因及血色素沉着病基因等遗传多态性可能造成儿童对铅毒性作用有不同的易感性 ,本文就此进行综述。     

Use of methodological search filters to identify diagnostic accuracy studies can lead to the omission of relevant studies

OBJECTIVE: To determine the usefulness of methodological filters in search strategies for diagnostic studies in systematic reviews. STUDY DESIGN AND SETTING: We made an inventory of existing methodological search filters for diagnostic accuracy studies and applied them in PubMed to a reference set derived from 27 published systematic reviews in a broad range of clinical fields. Outcome measures were the fraction of not identified relevant studies and the reduction in the number of studies to read. RESULTS: We tested 12 search filters. Of the studies included in the systematic reviews, 2%-28% did not pass the sensitive search filters, 4%-24% did not pass the accurate filters, and 39%-42% did not pass the specific filters. Decrease in number-needed-to-read when a search filter was used in a search strategy for a diagnostic systematic review varied from 0% to 77%. CONCLUSION: The use of methodological filters to identify diagnostic accuracy studies can lead to omission of a considerable number of relevant studies that would otherwise be included. When preparing a systematic review, it may be preferable to avoid using methodological filters.     

Evaluation of lead poisoning in an exposed pediatric population before and following control of the source

In the surroundings of a large lead mill, which emitted in the 70 years up to 250 t of lead per year and where the maximum allowable daily immission concentrations of 0.7 microgram/m3 were exceeded by a factor of 20-30, in children mean blood levels above 45 micrograms/100 ml blood were determined. At the beginning of the 80 years the mill had modernised the filter constructions. The emission was decreased to 10% of the original value. The immissions decreased by 50% and the blood lead level in children by 10 to 20%. It could be shown, that the soil was furthermore contaminated and vegetables and fruits contained increased lead levels. Additional measures are to be realised to diminish exposure. The situation described is an example for the long latency of positive changes in the environment and in the health state of the population following environmental preventive measures.