Preceding research has linked noise exposure, road traffic bring the dominant community source, with annoyance, which is an indicator of more serious, chronic health conditions. This study aimed to explore the association between residential road traffic noise and self-reported annoyance from an adult Indian population, residing close to roadways. The cross-sectional study used a questionnaire survey in an urban Indian municipality along roadways, where faηade noise assessment was made manually. The survey included randomly selected subjects aged 19-59 years, residing minimum of 10 years in the area and residing within 50 m of the roadways. Association of self-reported annoyance and noise exposure was examined by binary and multiple logistic regressions. The noise exposure was classified in units of 5 dB (A) from <65 dB (A) to 80 dB (A). Self-reported annoyance was marked at levels above 65-70 dB (A). A 67.5 dB (AA) is suggested as a threshold level. The association was statistically significant for female subjects with the adjusted odds ratio being 2.35 (95% confidence intervals: 0.99-5.58). Prevalence of annoyance was more for male subjects. Both age and period of residence were significant predictors of annoyance. Vulnerable age sub-groups were 34-40 years, followed by 50-60 years. The results of this study further suggest the association residential noise exposure near roadways and self-reported annoyance, among the study subjects.
Keywords: Annoyance, cross-sectional study, logistic regression, residential noise exposure
|How to cite this article:|
Banerjee D. Road traffic noise exposure and annoyance: A cross-sectional study among adult Indian population. Noise Health 2013;15:342-6
| Introduction|| |
Annoyance as an outcome is used to express the overall negative feelings such as displeasure, uneasiness, disturbance, discontent, and vulnerability, which leads to anxiety and stress. It can also be an indicator of somatic damage, loss of control and orientation, negative assessment of the noise source and high sound levels.  Noise annoyance is the most common exogenous indicator of stress built-up inside human beings and may be considered as a symptom of potential more serious health problems.  Road traffic noise is considered to be one of the major causes of noise annoyance in the urban community.  The complexity about noise impact assessment is that there is no residual effect, as with other pollutants, which can be estimated. Thus, studies world-wide have focused on the health indicator end points, among which annoyance as a subjective measure has been adapted with sufficient evidence. Although, the quantification of exposure to noise can be assessed with physical measures, noise annoyance is a subjective measure considered to reflect the internal exposure to noise.  Along with the other outcomes of epidemiological research related to exposure-effect of environmental noise, annoyance as an important endpoint has been widely accepted to envisage impact on the community.  Consequently, the European Union,  has recommended the use of noise annoyance as an indicator for evaluation of environmental noise exposure on the community. Current and past research has recognized that there is significant positive association between noise annoyance (as an external indicator) and amplified risk of cardiovascular disease manifestations, including arterial hypertension and ischemic heart disease. ,,,,, It has been reported that individuals expressing higher noise annoyance may have a significant 15.5% escalation in risk of arterial hypertension and a nearly significant 7% increase in the risk of ischemic heart disease (myocardial infarction and angina pectoris). Annoyance is also regarded as an indicator of sleep disruption including difficulty to fall sleep, changes in sleep stages, sleep fragmentation, which may lead to insufficient sleep, tiredness, loss of productivity, and develop medium term impacts such as chronic insomnia and cardiovascular diseases. ,, Studies have shown that short-term traffic noise exposure affects the autonomic nervous system (sympathetic nerve) and the endocrine system (pituitary and adrenal gland), which results in the release of stress hormones (adrenaline, noradrenalin, and cortisol), increased heart rate, blood pressure, vasoconstriction (narrowing of blood vessels). Such acute effects are not only characteristics of day time exposure (wake), but also during sleep and rest.
The association of traffic noise exposure and annoyance, in terms of effect indicators has never been reported from India.  Outcome of this study will add to the pool of current research and for the purpose of preventive measures. The outcome reported in the present study would be valuable in terms of establishing and/or intensification of environmental noise standards, directive and mitigation policies in India, and other developing countries. The objectives of the present study were to further investigate the association between residential road traffic noise exposure and self-reported annoyance, in an urban Indian adult sub-population residing close to roadways. Influence of factors like gender, age and residence period was also investigated, by stratification. The study also aimed to assess the noise level threshold for high annoyance and vulnerability in the age stratum and gender.
| Methods|| |
The pilot-study used cross-sectional data from a major public health survey (March-May) in the Asansol urban municipality, in the western part of India. This paper reported the results from a pilot-study, sub-sample from an ongoing citywide environmental health survey among adult individuals living in the municipality. For this study subjects a population sub-sample was taken from those residing within 50 m of roadways (highway, arterial and secondary roads) and living in the locality for a minimum of 10 years. A small sample of 221 subjects was taken for this study. The subjects (aged 19-60 years) were drawn from those dwelling within 50 m on each side of roads. Individuals were segregated into two noise exposure groups, where outdoor residential noise level below 65 dB (A) were taken as referent, , group while those within the ≥65 dB (A) levels were taken as the exposed group (case). ,, 10 years exposure was arrived as a criterion as because previous studies have proved that chronic exposure to noise is significantly related to health endpoints. , The questionnaire was intended to collect information about subjective annoyance response and associate them to different levels of noise exposures. For the present study, a comparable scale was used for the evaluation of outcome among the respondents. The scale was set to a range in order: "Not at all," "A little," "Moderately," "Highly," and "Severely," and the respondent was advised to state where his/her judgment is the more likely, based on the experience of last 12 months. Particulars of demographic characteristics including age, gender and residence period, were used to assess possible confounding.
Noise exposure measurements were performed manually for a period of 24 h in three shifts of morning (0700-1900 h), evening (1900-2300 h) and night (2300-0700 h) to arrive at the exposure indicator, L den (Equivalent Day-Evening-night noise, 24 h), which is well-documented as one of the indicator for noise annoyance and linked with sufficient evidence to be used to assess the degree of annoyance associated with road traffic noise.  Measurements were conducted near roadways and in close proximity to the nearest outdoor faηade of subjects dwelling. Subjects were stratified into residential noise exposure categories of 5 dB (A), with cut-off below 65 dB (A) as the referent group.
The association between residential road traffic noise exposure and self-reported annoyance was studied using logistic regression, and is reported as odds ratios (OR) with 95% confidence intervals (CI). All statistical analysis were conducted with STATA 9 (STATA Corp, USA) for windows. , Summary statistics and frequency tables were generated to identify missing data and assess the distribution of the variables. Quantitative variables were expressed as mean and standard deviation and categorical variables are presented as percentage. Differences between groups were compared using the Student-t test for continuous variables and Pearson's χ2 test for categorical variables, where a P < 0.05 was defined as statistically significant. Logistic regression with dichotomized (1 = highly annoyed (HA), 0 = not annoyed) outcome as dependent variables and gender (1 = men, 2 = women), age (5 category), residence period (2 category) and L den (5 category, 5 dB (A) interval) as predictors were entered. The model fit was assessed based on increase/decrease of the χ2 value when entering or removing the predictor variables. Significant predictor variables were further analyzed for interactions and potential confounding.
| Results|| |
The essential characteristics of subjects at study evaluation are shown in [Table 1]. Among the sample subjects, there were no significant differences between the exposed and referent groups in the baseline demographic characteristics except for residence period and gender. When considering residence period as continuous variable, differences were significant, whereas when stratified into two groups (≤20 years and >20 years), the difference become insignificant. The logistic regression analysis were conducted separately for male and female subjects as previous studies have shown gender differences in noise exposure and perceptions amongst them. The univariate ORs (OR, 95% CI) in relation to age and residence period, are given in [Table 2], for both gender. The estimates show significant association between self-reported annoyance and residential noise exposure, where the association is much stronger in men for both variables.
|Table 2: OR and 95% CI for self-reported annoyance in relation to independent variables and gender|
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[Table 3] and [Table 4] show the prevalence of self-reported annoyance along with OR and 95% CI due to exposure to residential noise above 65 dB (A) in male and female subjects respectively. Prevalence of annoyance was higher in male subjects (50%) in comparison to females (45.4%), for residential L den noise levels above 65 dB (A). Among male subjects, overall the association between noise and annoyance was not observed, either in the univariate or adjusted model. In female participants; however, the univariate model, with OR 2.73 (95% CI: 1.89-6.26) was significant.
|Table 3: Prevalence of self-reported HA and OR with 95% CI in male participants in relation to road traffic noise exposure|
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|Table 4: Prevalence of self-reported HA and OR with 95% CI in female participants in relation to road traffic noise exposure|
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[Figure 1] displays the relationship between self-reported annoyance (%HA) and residential road traffic noise emission among the studied subjects in different L den and age groups. Prevalence rate tended to moderately increase with increasing noise level up to 80 dB (a), and age. Imprecise estimates were observed, across all age groups, for L den level 65-70 dB (a), using both unadjusted and adjusted models. Increase in OR (95% CI) by 1.18 was observed between L den level 65-70 dB (a) and 70-75 dB (a) and more than double (2.21) between the L den levels 70-75 and 75-80. The OR although remained more or less similar between the 75 and 80 and much lowered in the >80 dB (a) subgroup. Highest annoyance was reported from age groups 34 years to 40 years, followed by the 50-60 age sub-groups for both genders. The trend was lower in the 29-33 age grouping. No significant results were obtained regarding the association of self-reported annoyance with either age or noise level.
|Figure 1: Adjusted odds ratio and 95% confidence intervals of self-reported annoyance (% highly annoyed) related to Lden, and age subgroups|
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| Discussion|| |
The present study suggests an association between the self-reported annoyance and residential road traffic noise exposure, assessed by the L den index and threshold noise level being the 65-70 dB (A) group with middle-aged subjects being more at risk. Self-reported annoyance has been used as indicator of subjective noise exposure in relation to other health studies, including hypertension, and ischemic heart disease. 
To the best of knowledge, this is the first study to quantitatively assess residential road traffic noise annoyance in an Indian sub-population. Previous studies in India have focused mostly on annoyance and noise relationships without reporting any effect estimate.  Results from the present study demonstrate that long-term noise exposure to road traffic noise may be associated with increasing risk of annoyance, when compared to non-exposed individuals as defined in the study, during the study period among those studies. Women were observed to be more annoyed at the same exposure level in comparison to men. The may be attributed to the gender difference in biological characteristics as well as due to the fact that women spend most of the day in their dwelling in this study area. This study will add to the pool of data in this subject, although the study is based on urban transportation system of a developing country like India, where vehicle movement, exposure pattern, road geometry and conditions, noise standards, and lifestyles, etc., are contrastingly different from the developed countries, from where much of the research has been reported. Although, previous studies have concluded that annoyance reaction is more or less similar across cross-cultural and variable groups. 
For the present study, limitations have to be considered. Since this was a pilot study, the sample size was very small and influence the effect estimates and not reach significant levels. The outcome indicator definition of annoyance may have been perceived differently across the respondents and it may have many consequences. The outcome was self-reported which typically might lead to overestimation of the terms since the respondents already knew that the study was regarding health effects of road traffic noise. Limitations can be considered in this study due to noise sensitivity related to stressful life, anxiety and other socioeconomic and health factors that were not considered for this study and not adjusted for. Overall, results from this study can be taken as a basis for further, more extensive research using a larger sample and including data on more confounding variables. The strength of this study was the in-depth analysis, including stratification of age and gender. Age was categorized to identify susceptible sub-populations, rarely used for noise annoyance studies. The use of residence period is also unique, with negligible studies reporting association of annoyance with period of residence.
Largely, in the absence of equivalent studies conducted on the Indian population all comparisons could only be conservatively drawn keeping in mind international research outputs. All datasets were complete, with no missing values, which could have led to errors, although the study lacked a representative sample size.
Thus, the results of this study should be judiciously used when comparing to previous studies conducted elsewhere. In interpreting the results of similar studies conducted elsewhere on the relationship between noise exposure and response, authors, with a few exceptions, often consider many other issues of the problem such as, for instance, culture or socioeconomic status, only as secondary topics and instead take considerable attention to only the classical factors like noise indices, or scales of community reaction. Hence, in the light of the latest findings, and in order to achieve a better understanding of the human reactive mechanism to noise exposure, more factors than just the noise level index must be taken into consideration.
The study conservatively suggests an L den threshold value of 67.5 dB (A) noise emission at the residential faηade to induce high annoyance, keeping the limitations in mind. This study also showed a dose-response relationship among the 34-40 years old subjects.
In conclusion, the results from this cross-sectional, pilot-study, which examined the relationship of noise exposure, and annoyance, suggest an association between self-reported annoyance (%HA) and residential traffic noise emission with age and period of residence being important factors, among those studied. The association was stronger among female and middle aged respondents. However, and including the other limitations, it cannot be excluded that there is the possibility that these findings may be influenced by other exogenic and endogenic factors.
| Acknowledgment|| |
This research paper was a part of the doctoral dissertation of the author. The author expresses sincere thanks to Dr. A. Gangopadhyaya, Dr. S. Bhattacharya of NIT, Durgapur, and Dr. S.K. Chakraborty of B.B. College, Asansol for supervision.
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79-Rabindranagar, Asansol, Burdwan - 713 304, West Bengal
Source of Support: None, Conflict of Interest: None
[Table 1], [Table 2], [Table 3], [Table 4]