空间流行病学和区域职业危害披露制度的构建

农民工已经成为中国经济发展不可或缺的重要力量,但是他们的健康正遭受着各种职业危害的威胁。主要原因可归咎于农民工对职业危害的信息不对称,用工单位和地方政府缺乏提供和监管职业危害防护的激励,以及忽略职业危害防护的低成本。该文初步探讨了利用空间流行病学,构建区域职业危害披露制度,以提高农民工和用工单位之间的信息透明度,提高地方政府和用工单位忽略职业危害防护的成本,从而改善农民工的职业健康。     

Applications of new technology in molecular epidemiology and their relevance to occupational medicine

Technological advances in molecular biology over the past 2 decades have offered more complex techniques that can be used to study the role of specific exogenous agents and host variables that cause ill health. Increasingly, studies in human populations use this new technology, combined with epidemiological methods, to shed light on the understanding of the biological processes associated with development of disease. This approach has many potential applications in occupational and environmental medicine (OEM), and some aspects of the work in this growing field are reviewed. An understanding of biochemistry and genetics at the molecular level, specific knowledge on metabolism and mechanisms of action, and epidemiology have become increasingly important for the OEM practitioner. This is necessary to consider the major question of validation and relevance of these molecular biomarkers. As end users, OEM practitioners should also consider the impact of these advances on their practices. For example, the availability of genetic tests to identify susceptible workers raises issues of ethics, individual privacy, right to work, and the relevance of such tests. Several studies have presented data on the association of environmental measurements and various biomarkers for internal and biologically effective dose, genetic polymorphisms, and early response markers. Given the limitations of individual molecular biomarkers in assessing risk to health, and the multifactorial nature of environmental disease, it is likely that such an approach will increase our understanding of the complex issue of mechanisms of disease and further refine the process of risk assessment.

 

     

Validation of exposure information in occupational epidemiology.

Exposure data may be inadequate mainly for two reasons; they may not comply with a reasonable exposure-effect model or they may be biased. In the use of historical data it is essential to keep track of what the data were supposed to mean when collected in the first place. Most measurements of air contaminants in work places are probably carried out to establish compliance or non-compliance with limit values. Sometimes measurements are also made to evaluate control measures. Unfortunately, measurement data acquired in this way may have very little to do with the true average exposure of employees. The influence of trends and variations in production on the exposure level is substantial. This influence is similar and coincidental in widely different industries. In addition the variations attributed to production levels, there can be important variations due to season.     

Meta-analysis in occupational epidemiology: a review of practice

OBJECTIVES: To describe past practice in meta-analyses found in occupational epidemiology, identifying the major issues that should be considered by researchers planning a meta-analysis in this setting. METHODS: An electronic search of relevant online databases was undertaken. Papers were included in the review if they contained a statistical synthesis of risks in an occupational health setting. RESULTS: Sixty reports of meta-analyses were identified, mostly in cancer. The number of meta-analyses has increased consistently over the last 20 years. A majority of studies focused on a mean overall effect, although more than half of them also investigated heterogeneity of results. Both fixed effect and random effects meta-analysis models were employed, the former more often, and in eight studies used despite a statistically significant test for heterogeneity. A large proportion of the meta-analyses included different effect measures in the statistical synthesis, for example, including standardized mortality ratios (SMRs) and standardized incidence ratios. Most meta-analyses limited to a single type of effect measure focused on SMRs. The vast majority of meta-analyses combined all studies regardless of variation in the extent of information on exposures. CONCLUSIONS: Meta-analyses in occupational epidemiology should properly explore and incorporate heterogeneity among studies. The meta-SMR is an important construct in this field, evidenced by a large proportion of cohort studies in the meta-analyses we identified. Controversy remains over the definition and validity of the meta-SMR. In addition, several other issues, notably dealing with heterogeneity in exposure, warrant further consideration.     

Bias in occupational epidemiology studies

The design of occupational epidemiology studies should be based on the need to minimise random and systematic error. The latter is the focus of this paper, and includes selection bias, information bias and confounding. Selection bias can be minimised by obtaining a high response rate (and by appropriate selection of the control group in a case-control study). In general, it is important to ensure that information bias is minimised and is also non-differential (for example, that the misclassification of exposure is not related to disease status) by collecting data in a standardised manner. A major concern in occupational epidemiology studies usually relates to confounding, because exposure has not been randomly allocated, and the groups under study may therefore have different baseline disease risks. For each of these types of bias, the goal should be to avoid the bias by appropriate study design and/or appropriate control in the analysis. However, it is also important to attempt to assess the likely direction and strength of biases that cannot be avoided or controlled.     

Latency analysis in occupational epidemiology

Allowance for prolonged disease induction and latency times is an important consideration in occupational epidemiology studies of cancer and other delayed effects of exposure. Two useful approaches for assessing prolonged induction and latency periods are (1) exposure lagging and (2) considering exposures only within moving time windows. The exposure weighting scheme proposed by Jahr2 to assess exposure burdens is another method that accounts for induction and latency, although not explicitly. These three approaches, which are shown to be special cases of exposure weighting, are illustrated with an analysis of lung cancer mortality among a cohort of workers from an asbestos textile plant.     

Exposure assessment in industry specific retrospective occupational epidemiology studies.

Quantitative estimation of exposure for occupational epidemiology studies has received increasing attention in recent years and, as a result, a body of methodological literature has begun to take form. This paper reviews the generic issues in the methodology of exposure assessment, particularly methods for quantitative retrospective assessment studies. A simple framework, termed an exposure data matrix (EDM), for defining and analysing exposure data is proposed and discussed in terms of the definition of matrix dimensions and scales. Several methods for estimation, interpolation, and extrapolation, ranging from subjective ratings to quantitative statistical modelling are presented and discussed. The various approaches to exposure assessment based on the EDM concept are illustrated with studies of lung disease among coal miners and other dust and chemically induced chronic occupational diseases. The advantages of validated statistical models are emphasised. The importance of analysis and control of errors in exposure assessments, and integration of the exposure assessment and exposure-response processes, especially for emerging occupational health issues, is emphasised.     

分子流行病学在职业性致癌研究中的应用

作者综合描述了分子流行病学基本概念的主要内容与传统流行病学的差异。阐明：１．分子流行病学是分子生物学与流行病学相结合的边缘科学;２．化学致癌物在体内的生成量及其与生物大分子结合的生物有效量与癌症发生有关;３．染色体异常综合症是癌症早期的生物效应;癌基因激活,抗癌基因失活是被启动了的细胞恶性转化所必须的;４．先天和后天获得的宿主因素可影响人体对致癌剂的易感性;５．建立生物样品库,进行前瞻队列研究可提供连续性观察结果及癌前癌后比较,为因果关系的时间顺序提供有效的依据     

A review of the healthy worker effect in occupational epidemiology.

This review article aims to anatomize sources of the healthy worker effect (HWE) and to summarize advantages and limitations of several approaches frequently proposed to eliminate the HWE. Although the HWE is frequently addressed in the context of selection bias, our review suggests that the selection of occupational cohorts with advantageous health status would preferably be addressed as a source of confounding biases. The authors also conclude that the exclusion of unhealthy workers at employment and the study of active workers are the two main sources of HWE, and that the use of the general population as a comparison group in occupational epidemiology should be avoided if possible. The authors encourage investigators to make distinctions between the underlying factors related to the use of the general population as the comparison group in occupational epidemiology.     

The epidemiology of occupational contact dermatitis

Occupational contact dermatitis (OCD) ranks first of all occupational diseases in many countries. The incidence rate is believed to be around 0.5–1.9 cases per 1000 full-time workers per year. Epidemiological studies play an important role in observing disease trends, analysing risk factors, and monitoring the effect of preventive measures. In this review article the lack of truly epidemiologic data on OCD and the difficulties of those studies are illustrated. The following issues are highlighted: case ascertainment and bias, the distribution of allergic and irritant contact dermatitis in the working population, the interrelationship between exogenous (allergens, irritants) and endogenous factors, the prognosis, the social and economic impact, and the need for intervention studies. Received: 26 January 1999 / Accepted: 24 April 1999     

职业流行病学中的回顾性队列研究方法(待续)

职业流行病学研究较多采用回顾性队列研究。进行回顾性队列研究先按暴露情况分成暴露组与非暴露组，以过去某个时点作为观察的起始时间，并以建立队列开始到当前时间作为随防时期，回顾比较队列成员各组的发病率或死亡率，判断该因素与发病或死亡有无关联及其程度。研究的结局可为死亡、发病或其他化验功能指标，要收集足够数量的历史记录或档案资料，对暴露组和非暴露组的研究对象应以相同的方法同时间进行随访，并追踪随访到各成员的结局，即观察终点。回顾性队列研究：分析工人的死亡率常用标化死亡比(SMR)及其显著性检验，比例死亡比(PMR)，此外还包括健康工人效应(HEW)，相对标化死亡比(RSMR)、职业暴露分级死亡率(MOX)等。回顾性队列研究的常见偏倚有选择偏倚，随防偏倚，信息偏倚，混杂偏倚，应采取适当的手段来控制。尽管回顾性队列研究有一定的局限性，但仍是目前国内外研究职业危害因素致病作用的切实可行方法。