Background
Environmental pollution must continuously be addressed, as the implication on our health could be disastrous. Our environment has to be sustainable for both our present and future generations (Guidotti et al., 2001). Obesity in the United States has been such a huge health issue in both adults and children. Being obese at a young age can increase the risk of developing future health complications such as diabetes and cardiovascular disease (CDC, 2016). Body mass index(BMI) is used to diagnose obesity because it relates an individual’s height to their weight (CDC, 2015). When a person surpasses a particular BMI, then they are classified as being overweight (CDC, 2015). This article studies the effects of roadside air pollution and second-hand smoke on body mass index. Studies that show the relationship between weight and environmental pollution can lead to stricter laws and targeted interventions.
Purpose
The rationale behind this study was the fact that previous studies had only focused on individual environmental factors and effects on body mass index. The author’s goal is to determine the outcomes of both second-hand smoke and roadside pollution on BMI increase over eight years. After that, the authors show that second-hand smoke and air pollution have greater effects on BMI when both occur simultaneously.
Study Hypothesis
The authors predicted a greater BMI effect as a result of combinations of second-hand smoke exposure and roads side pollution.
Sample
Researchers selected their sample from 4th-grade classes in 12 different communities. The sample initially included 3,887 participants, but they studied a total of 3,318 participants due to the authors BMI criteria and exclusions. Subjects had to have more than two different BMI numbers, as well as geographic markers for measurement of roadside pollution.
Methods
The authors conducted a longitudinal cohort study. The study was not randomized as participants were all in fourth-grade classes and were from twelve distinct communities. Researchers recorded both in utero and second-hand exposure. To determine the two cohorts, parents filled out questionnaires concerning the type of exposure, demographics, socioeconomic status and environment. During the 8-year period, researchers monitored participants annually. Data on roadside air pollution was collected and analyzed through Tele Atlas and Arc GIS. The Tele Atlas software, as well as the ArcGIS, was used to determine participant’s location and distance from the road. To account for miles, car pollution, location and other relevant factors, the researchers used CALINE4. The measure of NO concentration served as an indicator for both traffic pollution and air pollution. To rule out confounding effects in this study, researchers recorded and re-analyzed BMI differences based on access to healthcare, health condition, physical activity, education, and environments.
Results
During the eight-year follow-up, the average BMI increased from 18.3 to 23.6 and an overall average of 1% increase in obesity. The authors compartmentalized entry data by age, sex, ethnicity, education, personal behaviors, health care insurance, place of birth and environment. From the data gathered from the questionnaire, there were more participants exposed to second-hand smoke before enrollment in the study. Before the study follow-up, characteristics such as asthma, health insurance, environment, type of exposure to smoking, and environmental pollution indicated higher increases in BMI. During the end of the study, BMI difference for participants with one smoker and two smokers in the home were 0.95 and 1.77 points respectively. The BMI difference for participants who had both been exposed to roadside pollution and second-hand smoke while in utero were 1.14 and 1.27 point respectively. After accounting for possible confounding variables throughout the study, all results showed an increase in BMI. Additionally, the results showed a BMI increase of 2.15 points due to exposure from both SHS and NRP. NO analysis of the SHS and NRP effects also revealed a 0.34kg/m^2 increase in BMI from participants who had exposure to roadside pollution and an increase of 1.22kg/m^2 in BMI in participants exposed to second-hand smoke.
Conclusions
Being exposed to both roadside pollution and second-hand smoke leads to greater combined effects. During follow-up, participants exposed to either second-hand smoking or roadside pollution had slightly elevated BMI differences of 0.80 and 0.85 respectively. Near roadside pollution leads to a greater effect on BMI when associated with SHS. Adults who had lived in areas with high NRP, as well as high SHS, had higher BMI when compared to the subjects exposed to neither. Additionally, a graphical illustration of the results shows that to have a significant effect on BMI, elevated levels of roadside pollution and second-hand smoke need to occur simultaneously. NO is known as a primary pollutant and comes from car exhausts (Guidotti et al.,2001). To further clarify the effects of NRP and SHS on BMI, the researcher explains other possible factors such as PAH. PAH is a hydrocarbon that is found in second-hand smoke and roadside pollution and works by blocking the breakdown of fat, thereby leading to weight gain. Studies have linked PAH to lung cancers, skin cancer and stomach cancer (CDC, 2015). This article also discusses effects of particulate matter on BMI. Particulate matter is classified as a primary pollutant and could either be PM10 or PM2.5(Guidotti et al.,2001). Particulate matter measured during air quality checks is also linked to respiratory tract irritations and asthma exacerbation (CDC, 2016). In this article, particulate matter reduces the activity of the regulatory genes involved in triglyceride processing, therefore leading to weight gain.
Limitations
The likelihood of misclassification bias is common when using questionnaires. Parents may not remember every detail with regards to their child’s history which may influence the results, as more children exposed to second-hand smoke were reported to have a higher increase in BMI. In this study, the authors discounted the misclassification bias, because previous studies have not shown it to be the case. The authors discuss loss to follow-up, as data from 569 participants were not analyzed. In this study, all original subjects had similar BMI. Therefore, attrition was not a modifying factor. The authors accounted for various confounding variables but missed the factor of genetics. Although exposure to second-hand smoke and roadside pollution can increase BMI in adulthood, genetics also plays a role in obesity. Another factor discussed in this study is calorie intake. However, there was no evidence to prove any association with second-hand smoke, as well as roadside pollution.
Implications
This study gave great insight into the effects of air pollution on health outcomes. The effects of near roadside and second-hand pollution on BMI serves as a need for additional environmental laws and policies. This study fits right in with other studies associating air pollution with obesity, asthma and other respiratory health effects. The authors also discuss the increase in obesity in the state of California during a time when there was a decrease in second-hand smoke and roadside pollution. This example emphasizes obesity as an epidemic resulting from various determinants. This article did not discuss the effects of genetics on BMI. For future research, it is important to measure and compare the effects of genetics, predisposed conditions, and air pollution.