Sample/Number of Participants (provide descriptive statistics)
Level of Evidence
Findings (provide any inferential statistics)
Maria Ullerstam and Titus Kyrklund, (2010)
To evaluate the outcomes and results of previous epidemiological studies that determined the short and long term effects of exposure to traffic-related air pollution and the subsequent health effects as well as allergic reactions in children.
A representative sample of 700,000 in two categories of age groups
Case control studies in which in which disease and exposure status are measured simultaneously in a given population at certain points in time, hence allowing one to measure only the prevalence of disease. Additionally, longitudinal studies were also implemented
Evidence obtained from questionnaires as well as the analysis and use of prior cohort and case control studies to supplement the findings.
Significant positive associations between various measures of air pollution exposure and allergic sensitization in children. Results seem to be more consistent from cohort studies, Most studies
showed increased odds ratios for sensitization to inhalant allergens, especially to pollen in relation to outdoor levels of air pollution from traffic.
Difficulty in studying the long-term health effects due to the small but crowded differences within limited geographical coverage
Prashant Goswami & Jurismita Baruah (2014)
The identification of major players of acute respiratory disorders have been studied and the aspect of weather in addition to these pollutants in the development of respiratory diseases is described in this study.
1,400 children below the age of 5 years were studied
This study was adopted from an independent study carried out by a group and ARD deaths. Data was collected based on the morbidity and mortality. Interviews concerning the caretakers of the children were also conducted.
Corresponding morbidity and mortality rates accurately obtained from the government healthcare reporting system, followed by interviews to obtain data concerning ARD and related disorders. Observed pollution data obtained from the Pollution Control Board
In addition to acute respiratory diseases and deaths due to environmental pollution, low temperatures lead to diseases such as common cold, acute sinusitis,
Acute pharyngitis and acute tonsillitis. Furthermore, the pre-existing weather conditions play a significant role in the spread and incidence of respiratory diseases
The similarity in symptoms between other respiratory diseases and asthma raises the possibility of bias for an in-depth investigation since some of the observed cases thought to be ARD are actually asthma. Also, the use of gridded data makes it not easy to represent a broad exposure situation in a population.
Rice et al., (2001)
To use various exposure response
models to estimate the risk of
mortality from lung cancer due to occupational
exposure to respirable crystalline
A sample size comprised of 2342 white male diatomaceous miners and earth mining and processing
personnel who are exposed to crystalline silica dust
A cohort study design was used involving mortality studies and analyzed using the regression and proportional hazards models
Evidence from a single descriptive study based on a retrospective exposure assessment.
There was a significant risk of mortality from lung cancer that increased with cumulative exposure to respirable crystalline silica dust. The
predicted number of deaths from lung
cancer suggests that current occupational
health standards may not be adequately
protecting workers from the risk of lung
Exposure to silica and lung cancer have been troubled by inadequate data on confounding factors and lack of adequate information on exposure.
The possibility of uncontrolled confounding
of exposure to asbestos in this cohort
Blot et al., (1982)
To identify the factors responsible for the exceptionally high rates of lung cancer mortality in the Northeast coast of Florida.
321 male patients with lung cancer and 434 controls, or their next of kin
A case-control study involving interviews with lung cancer patients or their next of kin was carried out.
Evidence from descriptive and comparative study between the cases and the controls.
The elevated risks were associated with shipbuilding in this study which translated to high cancer rates mainly among those reportedly exposed to asbestos.
The greatest risk of lung cancer was highest among heavy cigarette smokers, accounting for the interaction between asbestos exposure and smoking
Presence of recall bias by the patients and the lack of knowledge with respect to exposure by the next of kin interviewed.
Presence of confounders.
Theresearch question addressed in the study table is “how does beingexposed to larger amounts of air pollution compared to decreasedexposure to the air pollutants affect the risk for respiratorydiseases or conditions and complications within a year?” All of thestudy samples were focused on determining more than one risk factorassociated with the development of respiratory diseases. Also, thestudies tackled additional factors that may not have been coveredadequately in other research studies. The different scenarios inthese selected readings have utilized various methodologies that canbe used to draw accurate conclusions concerning the relationshipbetween pollution and the breathing diseases or disorders. The searchcriteria were therefore oriented on the established factors that arehighly associated with respiratory illnesses as well as the preciseexamples of such conditions and their respective risk factors.
Themain designs utilized in these studies are longitudinal, case-controlstudies and cohort studies. The case-control study in the fourthinstance compared the patients with cancer to those without cancer(controls) by going back in time (retrospectively) to compare thelevels and frequency of exposure to the risk factors identified ashaving a relationship with the occurrence of Lung cancer. Thecontrols were selected randomly and matched regarding age, race andcounty of residence. On the contrary, the first and third studiesinvolved the cohort studies which include the following of theparticipants prospectively hence determining the initial participantscharacteristics of exposure. Also, the first study utilized alongitudinal approach in which variables were repeatedly observedover an extended period of time i.e. ten years. One of the studiesutilizes two separate summaries which are comprised of thecross-sectional studies while at the same time incorporating alongitudinal approach which encompasses both the case-control studiesand cohort studies as well. Centered on the levels of evidenceearlier expounded, these studies tend to fall under the fourth levelof proof due to the way in which they address a common problem,followed by diagnosis using systematic methodology for instancecase-control studies, providing recommendations on interventions thatcan work towards solving the problems, thus drawing appropriatereferences on the possible harms both common and rare, and theultimate importance of early detection and treatment of the issuebeing analyzed.
Inall these studies summarized above, the findings are quite clear thatthe presence of pollution increases the chances of developing acuterespiratory diseases. While most of the studies attributed the risksto cigarette smoking, asbestos and silicone compounds, the firstsurvey also indicated the role of weather conditions in the emergenceof these diseases and disorders. Also, the aspect of climate has beenassociated with an increase in the incidence and prevalence ofrespiratory diseases. The third and the fourth studies delve deeperinto the specifically associated risk factors including asbestos andsmoking as well as respirable silicon. The presence of these factorseither aggravate or give rise to the disease itself. For instance,the development of lung cancer was highest in the workers who wereexposed to both asbestos and also cigarette smoke. Therefore, theanswer to the research question is that the exposure to largeramounts of air pollution considerably increases the chances ofacquiring respiratory diseases, conditions, and complications, unlikea lower exposure to the same air pollutants within a year. The periodof exposure can be observed in the studies where exposure to highlevels of pollutants over time further increases the predispositionto illness. However, the studies do not efficiently answer thequestion since the yearly exposure was not measured and accountedfor. In other words, the research was spread out over periods longerthan one year hence the particular annotation focusing on a 12 monthperiod cannot be stated. Despite all this, the conclusions are clearthat high exposure repeatedly is directly proportional to the rise ofassociated health conditions.
Sampleselection in all of the studies was purposive because theparticipants are either having the state that is being observed or ispotentially exposed to the risk factors under scrutiny. This methodof obtaining the sample facilitates the easy acquisition of subjectswith the desired characteristics as well as provides the opportunityto utilize a broad range of research designs. The selected samplesizes seem to be adequate for the total population as well as thegeographical area covered. For instance, the range of 2342 minersobtained in the third research study is entirely representative ofthe total population working in the mining industry and exposed tosilica pollution. In the study done by Prashant Goswami &Jurismita Baruah (2014), the sample size of the children under fiveyears was obtained at a ratio of 2 incidences per 100 children. Thismight seem like a misrepresentation of the total study population butdue to a large number of children in this age bracket, thesymbolization can be considered valid to a considerable extent.Likewise, the first study employed the use of International Study ofAsthma and Allergy in Childhood (ISAAC) to come up with a figure of700,000 children from 56 countries based on epidemiological dataobtained concerning the prevalence of childhood asthma, allergicrhinitis, and atopic eczema. These characteristics account for theoverall target population and is thus representative.
Overall,the limitations of the studies revolve around the presence of biasesand confounders. With particular examples in the case-control studyof lung cancer, the presence of asbestos as a pollutant that cancause cancer forms a platform for the confounding bias betweencigarette smoking and asbestos. Similarly, exposure to silica andlung cancer also develops a confounding bias since other pollutantscan lead to lung cancer. Other limitations that are present includethe similarities among symptoms of respiratory diseases that maysometimes create a bias for a different illness. As seen, the studiesalso involved the use of questionnaires and interviews and at timeslack of education, knowledge and misunderstanding may lead to thecollection of data that is inaccurate. Furthermore, some participantsmay not be able to recall past events coherently making theinformation unreliable. This is also known as recall bias.
Allthe findings of these research studies indicate the evidence iscritical enough to propose changes in the practices or ideas forpractice. The study by Maria Ullerstam & Titus Kyrklund, (2010)suggest a relationship between traffic air pollution and thepre-existing conditions that lead to allergies and respiratorycomplications. This finding can draw a recommendation suggesting theuse of cleaner fuels and also change in policies that prescribe theminimum or the maximum allowed exhaust fumes in motor vehicles. Thesecond study which shows the role of weather in aggravatingrespiratory complications leads to the acknowledgment of theimportance of ensuring protection from low temperatures in theworkplace, schools and homes possibly through temperature regulationmethods and personal protection. The third study by Rice et al.,(2001) indicates that there is a high mortality rate that isassociated with exposure to silica. This calls for a more practicaland efficient approach that will ensure better occupational healthstandards that protect the well-being of the workers who arepotentially at risk. The last study conducted on the coast of Floridaindicated that shipbuilding workers who smoked had the greatestdanger of developing cancer as well as the correlation with the useof asbestos in the ship-making process. This finding is robust to thepoint that establishing regulations to minimize exposure to asbestoscoupled by the awareness and education on the effects of smokingmight be effective in the reduction of the cancer rates in that area.
Baruah, P. G. (2014). Quantitative assessment of relative roles of drivers of acute respiratory diseases. Scientific Reports.
Blot et al. (1982). Occupation and the High Risk of Lung Cancer. American Cancer Society.
Rice et al. (2001). Crystalline silica exposure and lung cancer mortality in diatomaceous earth industry workers: a quantitative risk assessment.
Swedich Environmental Protection Agency. (2010). Air pollution and children’s respiratory health. Stockholm.