Sources in the UK Various sources of routine health statistics may be useful to occupationa l health professionals practicing in the UK: \200 Reporting schemes for occupational inju ries and diseases: these include data reported to the Health and Safety Executive under RID DOR; and various voluntary reporting schemes co-ordinated by the Center for Occupational an d Environmental Health at the University of Manchester, as part of The Health and Occupatio n Reporting Network Periodic surveys of health and work conducted by the Health and Safety Executive, including the Labor Force Survey and Workplace Health and Safety Survey ( WHASS) Statistics of social security compensation for occupational injuries and prescribed industrial diseases Statistics of mortality and cancer incidence by occupation \200\224these are published peri odically by the Of \201 ce for National Statistics (ONS) and in the past were produced by its predecessor, the Of \201 ce of Population Censuses and Surveys (OPCS) General statistics of mortality and cancer incidence: again published by ONS, these may pro vide useful background data against which to evaluate patterns of disease observed in occup ational populations \200 Hospital Episode Statistics: published by ONS, these relate to h ospital admissions by cause and procedure. They do not include information on occupation, b ut include useful data on, for example, admissions for accidental pesticide poisoning. 34_Smedley_Chap34.indd 692 1/2/2013 12:57:23 PM ROUTINE HEALTH STATISTICS 693 1 All of the statistical sources listed have their individual strengths and limitations whi ch must be taken into account when they are used. Voluntary reporting schemes within The Health and Occupation Reporting Network (THOR) \200 Occupational Physicians Reporting Activity (OPRA) \200 SWORD \200 EPI-DERM Occupation al Skin Surveillance \200 Musculoskeletal Occupational Surveillance Scheme (MOSS) \200 Surveillance of Occupational Stress and Mental Illness (SOSMI) \200 Surveillance of Infec tious Diseases at Work (SIDAW) \200 Occupational Surveillance Scheme for Audiological Phy sicians (OSSA) Occupational Surveillance of Otorhinolaryngological Disease (THOR-ENT). Further information University of Manchester. Available at: M http://www.medicine.mancheste r.ac.uk/oeh/research/ thor/schemes/ UK National Statistics (2012). Available at: M http://www.statistics.gov.uk DWP. Statistics . Available at: M http://statistics.dwp.gov.uk/asd/index.php?page=iidb HSE Workplace healt h and safety survey (WHASS) program . Available at: M http://www.hse.gov. uk/statistics/publications/whass.htm HSE Self-reported work-related illness (SWI) and workplace injuries (LFS ). Available at: M http://www. hse.gov.uk/statistics/publications/swi.htm 34_Smedley_Chap34.indd 693 1/2/2013 12:57:23 PM CHAPTER 34 Epidemiology 694 Planning epidemiological research Unlike many other types of occupational health research, epidemiologi- cal investigations often do not require expensive equipment or facilities. Ho wever, even the simplest studies must be carefully planned and rigor- ously conducted. The starting point for any investigation is one or more study question(s). These should be both worthwhile and answerable. In other words, depend- ing on what is found, the informati on generated by the study should have the potential to affect how things are done in the fu ture. Protocols A protocol is essential for any epidemiological study. It is used in seeking ethi cal approval, permissions, and funding; as a guide to data collection and analysis; and as a reference when preparing reports of the study \201 ndings. The original study protocol, together with a note of any deviations that occurred as the study progressed, should be re tained so that they are available if required for the purposes of audit and governance. If the investigator is inexperienced in epidemiological research, or lacks relevant experti se (particularly in statistics), help should be sought in pre- paring protocols. The main e lements of a protocol are: \200 Background: this sets up the study question(s), summarizi ng relevant information from earlier research, the current gaps in knowledge, and why it is important t o address these gaps. It may also describe new technical advances that allow the gaps in kn owledge to be addressed in a way that was not previously possible Study question(s): these should be explicitly stated \200 Methods: this section should de scribe how the study questions will be addressed. It should include details of which subjec ts will be eligible for study, and how they will be recruited; what data will be collected about participants, and how these data will be analyzed to answer the study question(s). It may also be relevant to include information about the validity of methods for data collect ion Plans for publication \200 Statistical power: this gives an indication of con \201 dence that the study sample will not be unrepresentative simply by chance Ethical considerations: are there ethical issues associated with the research, and if so, how will they be addressed? Permissions and agreements (if relevant) \200 Funding (if relevant). 34_Smedley_Chap34.indd 694 1/2/2013 12:57:23 PM PLANNING EPIDEMIOLOGICAL RESEARCH 695 Ethical review Most epidemiological studies require formal review by a properly con- stitut ed research ethics committee (where there is doubt advice can be sought from the chair of t he committee to which the study would be referred). The relevant committee will depend on w ho is conducting the study and from where subjects will be recruited: \200 NHS-based rese arch: via the National Research Ethics Service (NRES) 1 \200 Non-NHS research: HSE have a n ethics committee that, although primarily concerned with HSE research, will consider extr amural research in the OH \201 eld according to set criteria. 2 Ethics committees normally specify the format in which they wish to receive applications. Other approvals Research that will take place within the NHS requires permission from the N HS organization(s) that will be involved. The National Institute for Health Research provid es a coordinated system to assist researchers in obtaining the necessary approvals. 3 Questionnaires Questionnaires are often used to collect epidemiological data. They may be s elf-administered or administered at interview. Questions may be open-ended (i.e. with free text answers) or closed \200\223ended (with a \201 nite set of options from which the ans wer is chosen). Important considerations in the design of questions are their validity (wil l they provide accurately the information that is sought?), understandability, and the ease with which the answers can be analyzed. Use of previously developed questions (e.g. from w idely used questionnaires) is often an advantage. Questionnaires should collect the informa tion that is likely to be needed to address the study question(s), but unnecessary detail s hould be avoided. 1 M http://www.nres.npsa.nhs.uk/ 2 HSE Research Ethics Committee. Available at: M http://www.hse.gov.uk/research/ethics/inde x. htm 3 NICE (2012). Gaining NHS Permission for clinical research . Available at: M http://www.cr ncc.nihr. ac.uk/about_us/processes/csp 34_Smedley_Chap34.indd 695 1/2/2013 12:57:23 PM CHAPTER 34 Epidemiology 696 Investigation of disease clusters A cluster of disease is an unusually high number of cases in a de \201 ned population over a time period during which fewer than one or two cases w ould be expected. Disease clusters are not infrequent in occupational populations. Occasionally they result f rom exposure to a hazardous agent or activity in the workplace, but much more often they si mply represent a chance coincidence. Nevertheless, they can be a major cause of anxiety for both employees and managers, and require proper assessment. The assessment of occupational clusters entails a staged approach, the extent of investigat ion depending on the level of scienti \201 c suspicion that an occupational exposure is re sponsible and also the level of concern in the workforce and management. Characterization of index cases A \201 rst step is to characterize the index cases that h ave given rise to con- cern. The aim should be to establish: \200 The precise diagnosis o f each case \200 The occupational exposures that the cases share in common. If the cases, in fact, suffer from different diseases that are unlikely to have the same causes, or they do not share any potentially hazardous occupa- tional exposures, then the level of scienti \201 c suspicion is low, and more detailed investigation may not be necessary. Further investigation If further investigation is required, the next steps are to: \200 S earch readily accessible sources of information (e.g. company pension \201 les and occupa tional health records) for any additional cases with the same diagnosis/diagnoses and expos ure(s) as the index cases Estimate the expected frequency of the relevant diagnosis/diagnoses in all employees with t he same exposure(s) as the index cases. This gives an indication of how unusual the cluster is Review published scienti \201 c literature regarding known and suspected causes of the disease(s) suffered by the index cases. Look for indications that a shared oc cupational exposure might have a causal role \200 Establish how frequently the shared exp osures of the index cases occur elsewhere, and what is known about their potential adverse effects. \200 If the same exposures commonly occur in other occupations or circumstances, then any increased risk of disease might be expected to apply also in these other situations. If the shared exposures have known toxic effects that are consistent with an increased risk of the disease(s) in the index cases, then the level of s cienti \201 c suspicion is increased. (For example, a cluster of cancer would be more susp icious if there were shared exposure to a known mutagen). 34_Smedley_Chap34.indd 696 1/2/2013 12:57:23 PM INVESTIGATION OF DISEASE CLUSTERS 697 Formal epidemiological studies If additional investigation is required beyond what has alre ady been described, then often it will take the form of a formal epidemiological study. Suc h a study may be conducted in the workforce that experienced the cluster, with the aim of p roviding more precise estimates of risk in relation to speci \201 c exposures. However, it must be remembered that clusters only come to attention because they are unusual, and ther efore a study in a workforce with a disease cluster can be expected to show elevated risks for the disease concerned. For this reason, a stronger design is to conduct a study in a se parate population with similar exposures to the index cases. If a study of this sort provid es independent evidence of excess disease, the case for an underlying occupational hazard b ecomes more compelling. 34_Smedley_Chap34.indd 697 1/2/2013 12:57:23 PM CHAPTER 34 Epidemiology 698 Cross-sectional surveys In a cross-sectional survey information is collected at a single po int in time (or over a short period) about the prevalence of health outcomes and/or their d eterminants in a de \201 ned population. In occupational health, information from cross-sectional surveys may be used for several purposes: \200 Planning and prioritizing interventions: e.g. the prevale nce of stress-related illness might be assessed in a workforce to decide whether changes were need ed in working methods or styles of management Monitoring the impact of measures to control hazardous exposures: e.g. the prevalence of se nsorineural deafness might be assessed to check the effectiveness of controls on noise expo sure, or personal exposures to an airborne pollutant might be measured to check that local exhaust ventilation was working as intended Investigating associations between exposures and disease: e.g. whether the prevalence of de rmatitis is unusually high in workers handling a new material. Cross-sectional studies of disease causation Cross-sectional surveys are attractive as a me ans of investigating causes of disease in that they can often be conducted relatively quick ly and cheaply. However, special care is needed in their interpretation. \200 Risks may b e underestimated because of biases in the selection of subjects for study. This is a partic ular concern when the disease of interest is suf \201 ciently disabling that it causes peo ple to leave the job in which it arose, or where its symptoms are exacerbated by continuing exposure to the causal agent, again leading people to move from the job that caused it. Fo r example, the risk of asthma from an occupational allergen might be missed if sensitized i ndividuals rapidly moved to other work and therefore were not included in a cross-sectional sample of exposed workers The cross-sectional design may make it dif \201 cult to distinguish cause from effect. For example, a high prevalence of pathological drinking in publicans might occur because heavy consumers of alcohol preferentially seek employment in bars, or because work as a publican makes people more prone to drink heavily, or both. For these reasons, cross-sectional studies of disease causation work best for less serious diseases that are unlikely to cause a change of job, and are unlikely to impact on the expo sures under investigation. 34_Smedley_Chap34.indd 698 1/2/2013 12:57:23 PM This page intentionally left blank CHAPTER 34 Epidemiology 700 Cohort studies In a cohort (longitudinal) study, people with known exposure to a risk fac- tor (e.g. a hazardous occupational exposure) are followed up over time, and their subsequen t health or mortality is compared with that of controls that were unexposed or exposed at a lower level. Cohort studies can be used to estimate both attributable and relative risks. The method has been widely used to investigate known and suspected causes of occupational c ancer, but can be applied to many other types of health outcome. Assessment of exposure Exposures must be assessed not only to the risk factor(s) of prime i nterest, but also to potential confounding factors. Depending on the study ques- tion and t he practicality of data collection, the exposure ascertained may be at a single point in ti me (most often the time of entry to follow-up), over a period up to a speci \201 ed point in time, or right through to the time of exit from follow-up (this requires repeated assess ment of exposures throughout the follow-up period). Many different methods of exposure asse ssment may be employed, including the use of questionnaires, employ- ment records, occupati onal hygiene measurements, and bio-monitoring data. Often a job-exposure matrix is applied to translate job titles into agent-speci \201 c exposures. Assessment of health outcome The methods by which health outcomes are ascertained will depe nd on the study question, and on practical and ethical limitations. They may be assessed co ntinuously throughout follow-up or at one or more time points during the follow-up period. Methods include the use of death certi \201 cates, cancer registrations, and follow-up que stionnaires, physical examinations, and clinical investigations. To prevent bias, methods f or ascertaining health outcome should not vary in relation to the risk factors under study. Retrospective cohort studies Particularly in the study of occupational carcinogens, (where prolonged follow-up is usually required to obtain statistically meaningful results), cohort studies are often conducted retrospectively. This requires that cohort members can be iden ti \201 ed retrospectively and their exposures assessed in a way that it is not biased in relation to subsequent health outcome. It is also necessary that the relevant health outcom es can be reliably assessed in retrospect. Comparisons with the general population Occupational cohort studies of mortality and cancer incidence commonly use disease rates in the general population (national or regional) as a com- parison. This has the advantage of giving statistically robust control data at relati vely low cost, and is valid provided it can reasonably be assumed that the exposures of int erest are negligible in the general population when compared with those in the study cohort . 34_Smedley_Chap34.indd 700 1/2/2013 12:57:24 PM COHORT STUDIES 701 Healthy worker effect In cohort studies that compare mortality in an occupational group wit h that in the general population, bias may arise from a \200\230healthy worker effect. \200\230 This occurs because employed people tend on average to be healthier than the popul ation at large. In particular, people with chronic disabling disease are liable to be selec tively excluded from employment. Thus, when followed up over time, employed populations ten d to have lower than average death rates from causes, such as chronic respiratory disease, for which death is often preceded by a prolonged period of disability. Statistical analysis Various statistical methods are applied in the analysis of cohort stud - ies, depending in part on the exact study design and the type of health outcome. One tech nique that is widely used when comparing mortality or cancer incidence in an occupational c ohort with that in the general population is the \200\230person-years method \200\231. Thi s entails \201 rst summing the number of years for which cohort members were under follow -up in dif- ferent combinations of age and calendar period. The age- and calendar period-sp eci \201 c disease rates in the general population are then applied to these person-years of follow-up to obtain an \200\230expected number \200\230 of cases for each combination o f age and calendar period. Next, the expected numbers are summed across all combinations of age and calendar period. Finally, the observed number of cases is divided by the total exp ected number to give a SMR or standardized incidence ratio (SIR). 34_Smedley_Chap34.indd 701 1/2/2013 12:57:24 PM CHAPTER 34 Epidemiology 702 Case-control studies In a case-control (case-referent) study people with a disease of inter est (cases) are identi \201 ed, and their past exposure to known or suspected causes is co mpared with that of controls (referents) that do not have the disease, associations general ly being summarized by odds ratios. Sometimes case-control studies are \200\230nested \200 \230 within a larger cohort inves- tigation, but even where they are not; they can be viewe d as an ef \201 cient method of sampling from a theoretical cohort investigation. Essentia lly, exposure information is collected about all of the cases of disease in the study popul ation and time period, but about only a representative sample of those who are not cases. Recruitment of cases The source of cases and method of ascertainment should be explicitly d e \201 ned. Ideally, cases should have incident (newly presenting or newly diagnosed) dise ase. Prevalent or fatal cases may be used as an alternative, but associations may then re \202 ect in \202 uences on recovery or fatality as well as on incidence. Often an attempt is made to recruit all cases in a de \201 ned study population and time period, but this i s not essential, and the source population for the case group may only be notional (e.g. th e catchment population of a hospital). Selection of controls Controls should be representative (in terms of their exposures to ris k factors and potential confounders) of the non-cases in the population (de \201 ned or no tional) that gave rise to the cases. A second objective is that they should provide informa tion on exposures of similar quality to that for cases (the ideal of perfect accuracy is ra rely achievable). Often it is impossible to achieve both of those aims simultaneously, and compromise is necessary. Two sources of controls, commonly employed are patients with other diseases and people selected at random (or effectively at ran- dom) from the study populat ion. Matching The control of confounding in case-control studies is through appropriate statisti cal analysis, but this is sometimes made more ef \201 cient by matching controls to cases (either individually or in groups) according to the pres- ence or levels of potential confo unding factors such as sex and age. Where matching is used, the exposures of controls shoul d represent those of all non-cases in the source population with the relevant matching crit eria. Ratio of controls to cases Where exposure information can be obtained as easily from cases as con- trols and there is no practical limit to the available pool of cases, statistical e f \201 ciency will be maximized by recruiting equal numbers of cases and con- trols. Where cases are in limited supply or control data can be ascertained more easily than data from cases, the statistical power of a study may use- fully be enhanced by taking a higher ratio of controls to cases. However, 34_Smedley_Chap34.indd 702 1/2/2013 12:57:24 PM CASE-CONTROL STUDIES 703 the return from this diminishes as the ratio increases, and control \200\224case ratios gre ater than four are rarely worthwhile. Exposure ascertainment Exposures must be assessed both to risk factors of interest, and als o to potential confounding factors. Various sources of information are used, including ques tionnaires, historical records, and biomarkers (provided these re \202 ect exposures befor e disease onset and are not modi \201 ed by the occurrence of disease). If exposures are a scertained by questionnaire and the recall of cases is more complete than that of controls, bias may result with spurious in \202 ation of risk estimates. 34_Smedley_Chap34.indd 703 1/2/2013 12:57:24 PM CHAPTER 34 Epidemiology 704 Experimental studies An experimental study assesses the effect of a planned intervention on outcomes of interest. Outcomes that may be relevant in occupational health research includ e: \200 Disease incidence, prevalence or mortality \200 Incidence of other adverse even ts (e.g. dangerous occurrences or near-miss accidents) Biomarkers of sub-clinical health effects (e.g. acetyl cholinesterase activity) Biomarkers of exposure to hazardous agents \200 Measures of attitude or behavior. Occasio nally, an intervention may involve deliberately exposing subjects to a hazardous agent at l ow levels, looking for evidence of minor subclinical effects. Mostly, however, it is ethica l to study the impact only of potentially bene \201 cial interventions (e.g. aimed at cont rolling a hazardous exposure or practice). Comparisons may be between a new intervention an d standard practice, or between two or more different interventions. Study designs Various study designs may be employed, depending on the nature of the interve ntion(s) and outcome(s) of interest. Simple \200\230before and after comparisons \200\230 Outcome measures are assessed in the same subjects or groups before and after an intervention, looking for changes that might be attributable to the intervention. The weakness of this design is that results may be confo unded by other determinants of outcome that change over time in parallel with the intervent ion. Non-randomized, controlled comparisons Subjects or groups receiving an intervention are com pared with controls that receive a different intervention or are managed according to stand ard practice. At baseline (i.e. prior to the intervention), controls should be as similar a s possible to the subjects receiving the intervention in character- istics that are known o r likely to predict the outcomes under study. This may be easier to achieve if the outcome is the change in a parameter fol- lowing the intervention rather than its absolute value. Randomized controlled interventions People or groups with similar baseline characteristics are randomly assigned to receive the intervention or to serve as controls, and their subseq uent outcomes are compared. If there is marked heterogeneity of subjects or groups at basel ine, they should be strati \201 ed before randomi- zation according to likely predictors o f outcome, and then randomized within strata. The advantage of randomized controlled interv entions is that when randomization is applied to large numbers of individuals or groups; it tends to eliminate confounding effects even for unrecognized confounders. However, when on ly a few individuals or groups are avail- able for study, the bene \201 ts of randomizatio n are minimal, and it is usually better to use a non-randomized companion. 34_Smedley_Chap34.indd 704 1/2/2013 12:57:24 PM EXPERIMENTAL STUDIES 705 Blinding Sometimes it is possible to \200\230blind \200\230 subjects, those implementing a n inter- vention, and/or those assessing outcome measures as to whether an individual or gr oup received a particular intervention. This can have two advantages: \200 Prevention of confounding that might occur if knowledge of the intervention led to other parallel changes (either deliberate or subconscious) Reduction of potential bias in the assessment of outcomes (e.g. from placebo effects). Blinding is particularly important where the assessment of outcomes depends on subjective j udgment by the participant or an investigator. 34_Smedley_Chap34.indd 705 1/2/2013 12:57:24 PM This page intentionally left blank Section 9 Environmental medicine 35 Environmental protection 709 35_Smedley_Chap35.indd 707 1/2/2013 12:59:04 PM This page intentionally left blank 709 Chapter 35 Environmental protection Environmental medicine 710 Health Protection Agency 712 Outdoor air pollution 714 Indoor ai r pollution 716 Water pollution 718 Soil pollution 720 Food contamination 722 35_Smedley_Chap35.indd 709 1/2/2013 12:59:04 PM CHAPTER 35 Environmental protection 710 Environmental medicine General principles \200 Environmental exposures, while sharing man y attributes with occupational exposures, are often more subtle. They are generally of much lesser degree (e. g. pesticide exposure in farming communities, outdoor air pollution) and the effects are no t so easily attributable to the exposure Where an environmental exposure is recognized to affect health, the aim of the physician or regulator is to protect the individual by removing or reducing exposure, e.g. reducing amb ient air pollution by improvements in engine and fuel technology \200 This exposure, effe ct, control paradigm (Fig. 35.1): provides a framework for understanding how a speci \201 c exposure might lead to an individual health effect identi \201 es where control measures might be instituted, e.g. by reducing personal exposure or reducing emissions by legislation. Exposures \200 Routes of exposure: \200 inhalation \200 through the skin \200 inges tion \200 other exposures (noise, vibration, UV light) Quanti \201 cation of exposures: questionnaire or structured interview, but relies on memory, often of distant events direct measurement, e.g. air quality \200 biomarkers, e.g. blood lead (Pb) levels Modeling, by using existing information to develop predictions of exposure where direct measurement cannot be made. Exposure and outcome \200 Once an estimate of exposure has been made, this needs to be ma tched against a speci \201 ed outcome. During this process all recognized confounders must be identi \201 ed and measured (where possible), so that interpretation is valid Vulnerable groups within any population are the young (including the unborn child), the eld erly, and the in \201 rm. These groups may show adverse effects of environmental exposures at lower exposures than healthy adults of working age. Control \200 Control measures depend on route(s) of exposure and may be multiple (e.g. pesticides). An understanding of the proportion of the total dose from each route is essential when considering control \200 The precautionary approach is usually us ed, where, without waiting for cast-iron proof that exposure A via route B causes disease C , action is taken to reduce overall exposure. 35_Smedley_Chap35.indd 710 1/2/2013 12:59:04 PM ENVIRONMENTAL MEDICINE 711 Practicalities of assessing environmental exposures and health impacts The effect of an env ironmental exposure may come to notice through the following: \200 Increased exposure : r ecognition that a population is exposed to a speci \201 c substance or pollutant mix, e.g. particulate air pollution in cities Disease clustering : recognition of a cluster of a speci \201 c disease in time and/or place (e.g. outbreaks of infectious disease) By analogy: with exposure to other proven exposure/outcome situations elsewhere, e.g. curre nt concerns around exposure to nanomaterials bearing in mind the proven adverse effects of asbestos and the considerable delays in accepting the true health impact of that material. Influences Fixed (e.g. genes, priming) \200 Variable (e.g. co-exposures, infections) No personal health effect Personal exposure Occupational vs wider environment Personal health effect Emissions Population exposure Population health effect Policy Influences Mechanisms \200 Multiple \200 Independent Size of effects \200 Acute & chronic \200 Political climate Fixed (e.g. geography) \200 Variable (e.g. activity, meteorology) Fig. 35.1 Health effects of an environmental hazard. 35_Smedley_Chap35.indd 711 1/2/2013 12:59:04 PM CHAPTER 35 Environmental protection 712 Health Protection Agency Structure of the Health Protection Agency The HPA was set up in 20 03, as a Special Health Authority. However, it became an independent public body in 2005, w hen it was combined with the then NRPB. It is made up of \201 ve main elements: \200 HP A headquarters \200 Center for Infections \200 Center for Emergency Preparedness and Re sponse \200 Center for Radiation, Chemical and Environmental Hazards \200 National Inst itute for Biological Standards and Controls. Role of the Health Protection Agency The Health Protection Agency \200\231s role is to prot ect the public health. It covers chemical, biological, radiological or nuclear threats. The role of the Health Protection Agency (M http://www.hpa.org.uk/AboutTheHPA/) is divided int o the following areas: \200 Chemical hazards \200 Biological hazards \200 Radiation h azards \200 Emergency response \200 Infectious diseases. The Health Protection Agency i s the UK \200\231s lead body on health protection, but it also has responsibility to provid e local health protection services in England. This local health protection role is ful \201 lled by Health Protection Scotland (HPS) in Scotland, the National Public Health Servi ce in Wales and by the Department of Health, Social Services and Public Safety in Northern Ireland. The HPA has to work closely with other relevant agen- cies in order to ful \201 l l their work, notably the Department for Environment, Food and Rural Affairs (DEFRA) and th e Environment Agency. Its work will be subsumed into the Department of Health in 2011 \200 \22312. Remit of the centers \200 Center for infections: communicable disease surveillance \200 advising government on infectious diseases \200 microbiological reference laboratory \200 outbreak investigation for major epidemics or u nusual infections Center for Emergency Preparedness and Response: monitoring and assessment of new, emerging or re-emerging infectious illnesses developing and maintaining Britain \200\231s capacity to deal with emergencies such as disease outbreaks or chemical releases including acts of terrorism. Thi s includes training emergency services, and running exercises to test responses Providing advice on the management of chemical, biological, radiological or nuclear incidents (CBRN) Center for Radiation, Chemical and Environmental Hazards: Radiation Protection Division 35_Smedley_Chap35.indd 712 1/2/2013 12:59:05 PM HEALTH PROTECTION AGENCY 713 Chemical Hazards and Poisons Division \200\224offering advice on chemical incidents including \201 res, chemical leaks and pollution (the Air Quality and Noise section is part of HPA); the National Poisons Information Service (NPIS) provides adv ice to NHS staff on the management of individual patients. National Institute for Biological Standards and Controls: the National Institute for Biological Standards and Controls (NIBSC) mission is to assure the quality of biological medicines. Relevant legislation The Health Protection Agency Act 2004. 35_Smedley_Chap35.indd 713 1/2/2013 12:59:05 PM CHAPTER 35 Environmental protection 714 Outdoor air pollution \200 Air pollution is a mix of different particles, gasses, and che micals, the proportions of which vary by source and by site The major contributors are anthropogenic, although there can be major contributions from natural sources under some circumstances \200 Control of air qua lity is exercised at national government level, but can only deal with locally produced anthropogenic emissions as natural sources are uncontro llable as, to a certain extent, is transportation of air pollution from one country to anot her Continued exposure to polluted air confers a greater risk to health than episodes, although the Great London Smog of December 1952, which killed at least 4000 individuals, was critic al as it led to the introduction of the Clean Air Act 1956. Content and sources Particles Sources \200 Vehicle emissions \200 Industry \200 Power generation \200 Natural: sea salt, disturbed dust, volcanoes Measures \200 Mass (expre ssed as g/m 3 of air) gravimetrically \200 PM 10 \200\224particulate matter <10 m in diameter \200 PM 2.5 \200\224particulate matter <2.5 m in diameter \200 re \202 ectance \200\224i.e. by measurement of blackness of a \201 lter (Black Smoke) light scattering \200\224expressed as PM 10 , PM 2.5 \200 numbers \200\224expressed as particle numbers per cubic centimeter of air. These measures are usually expressed as 24-h or annual means. Gasses \200 Sulfur dioxide: largely from industry or power generation \200 Nitrogen dioxide: 2 pollutant from vehi cles \200 Ozone: 2 pollutant from action of UV light on oxides of nitrogen and hydrocarbons Carbon monoxide: from vehicles. Gasses are expressed as ppb or g/m 3 and for the timesca le relevant to their air quality standard . Other substances \200 Carcinogens: \200 benzene \200 1,3-butadiene \200 PAHs Lead. 35_Smedley_Chap35.indd 714 1/2/2013 12:59:05 PM OUTDOOR AIR POLLUTION 715 Health effects Diffuse pollution \200 i Particles are associated with i mortality and i h ospital admissions for cardiopulmonary disease on a day-to-day basis Similar effects are seen with ozone and sulfur dioxide, but of lesser degree Effects on asthma are limited to hospital admissions and, inconsistently, to symptoms and lung function Effects of long-term exposure on disease prevalence and severity may be more marked Association with incidence of lung cancer but not other cancers shown in the USA. Point source pollution \200 Emissions from point sources can cause clusters of disease (e .g. soyabean dust emissions from the docks in Barcelona in the 1980s led to outbreaks of acute asthma) The worst recorded peacetime incident occurred in Bhopal, India, in 1984 when an incident a t the Union Carbide (India) Ltd plant led to the release of a cloud of methyl isocyanate ga s causing over 3800 deaths More usually, concerns arise about the potential for an identi \201 ed source to be a cause of disease clusters. See Chapter 34 in Investigation of disease cluste rs Many disease clusters are chance events unrelated to point sources of pollution, but unders tandably generate considerable public concern. Control \200 Air quality standards are based on health effects worldwide even though air pollution also impacts on crop yields and the integrity of buildings Responsibility for air quality falls to local councils in the UK. Relevant guidance and legislation \200 Clean Air Act 1993 (c. 11). Stationery Of \201 ce , London \200 Air Quality Limit Values Regulations 2001. Stationery Of \201 ce, London. Similar regulations apply across the UK The UK \200\231s archive of air pollution measurements. Available at: M http:// www.airquality.co.uk/archive/index.php The UK \200\231s air quality strategy can be viewed at: M http://www.defra. gov.uk/environment/quality/air/air-quality/approach/ 35_Smedley_Chap35.indd 715 1/2/2013 12:59:05 PM CHAPTER 35 Environmental protection 716 Indoor air pollution \200 In the developed world 90% of time is spent indoors \200 In p arts of the developing world much greater time is spent outdoors \200 Indoor air quality is not subject to legislation except in the workplace, where occupational exposure standards apply in some settings. Indoor pollutants \200 Environmental tobacco smoke (ETS) \200 Allergens, including mold s \200 Indoor penetration of pollutants from outside (notably particles) \200 Cooking f ume \200 Settled dust \200 Micro-organisms \200 Endotoxins \200 Nitrogen dioxide (N O 2 ) from gas cookers and \201 res \200 Carbon monoxide (CO) faulty gas appliances \200 Ozone \200 Kerosene products \200 Biomass fuel combustion, e.g. plant material or agricultural waste \200 VOCs, e.g. formaldehyde \200 Radon. Health effects \200 ETS exposure: respiratory symptoms in children \200 lung cancer Biomass fuel: lung cancer \200 chronic bronchitis/chronic obstructive pulmonary disease (COPD) Cooking fume: \200 lung cancer \200 possibly exacerbation of asthma Radon: lung cancer \200 Sick building syndrome occurs in arti \201 cially ventilated bui ldings: the exact cause is unknown but it appears to relate to air exchange rates and tempe rature. It presents with a range of symptoms (see b p. 334, Sick building syndrome): \200 headaches \200 tiredness \200 poor concentration \200 sore throats \200 nasal symp toms \200 tight chest \200 inability to wear contact lenses/dry eyes. 35_Smedley_Chap35.indd 716 1/2/2013 12:59:05 PM INDOOR AIR POLLUTION 717 Control \200 There are no indoor air quality standards. Such controls would raise issues of individual civil rights By law anyone installing or servicing gas appliances must be Gas Safe registered Landlords are required to have gas appliances serviced annually, keep records for two years and give new or existing tenants a copy of the current safety certi \201 cate. Relevant legislation and guidance Gas Safety (Installation and Use) Regulations 1998. Stati onery Of \201 ce, London. 35_Smedley_Chap35.indd 717 1/2/2013 12:59:05 PM CHAPTER 35 Environmental protection 718 Water pollution Safe drinking water 1 is essential for life. Microbiological contamination is well recognized, but contamination by metals, etc., also occurs. Pollution follows spill s, industrial discharges, mining (especially abandoned mines), agricultural run-off and lea chate from land \201 ll. Naturally occurring metals may affect water quality. Pollutants m ay be point sources such as indus- trial discharges or diffuse pollutants including agricul tural run-off of animal wastes. Contamination of estuarine and inland seas may lead to seve re impacts e.g. the Aral Sea disaster. Water is divided into surface waters (streams, river s, lakes) and ground water ( 98% of available fresh water). These are closely linked and ex change occurs between them.