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Year : 2002  |  Volume : 4  |  Issue : 16  |  Page : 57--63

Urban noise in the City of Sao Paulo, Brazil : An important problem of public health

Carolina Moura-de-Sousa, Maria Regina Alves Cardoso 
 Faculdade de Saúde Pública - Universidade de São Paulo (School of Public Health - University of São Paulo -Departamento de Epidemiologia, São Paulo, Brazil

Correspondence Address:
Carolina Moura-de-Sousa
Institution: Faculdade de Saúde Pública - Universidade de São Paulo (School of Public Health - University of Sao Paulo) - Departamento de Epidemiologia, Av. Dr. Arnaldo, 715. sala 216, CEP 01246-904, São Paulo - SP
Brazil

Abstract

Objectives. To estimate the sound pressure levels in areas with heavy and with local traffic in the city of Sao Paulo and compare the data obtained with the thresholds established by the local law. Methods. Twenty-eight points in roads with heavy and local traffic were chosen. The measurements were done Monday to Friday, 8 am to 5 pm, using a 2236 Mediator (Briiel & Kjaer) following the International Standard (ref. no. 1996/1982 1,2,3). Each point was measured a number of times to produce a standard error lower than 1 dB. Results. The equivalent continuous A-weighted sound pressure level (Leq) for the roads with heavy traffic ranged from 70.88 to 80.18 dB(A), mean 75.88 dB(A) (95% CI: 74.49; 77.27) and the maximum peak (MaxP) ranged from 102.47 to 108.37 dB(C), mean 105.63 dB(C) (95% CI: 104.59; 106.68). For the roads with local traffic we observed: Leq from 50.82 to 66.88 dB(A), mean 61.11 dB(A) (95% CI: 57.97; 64.26) and MaxP 83.13 to 97.33 dB(C), mean 92.81 dB(C) (95% CI: 89.80; 95.82). There was a strong evidence, p < 0,001, in favour of the difference between the two types of traffic roads regarding the sound pressure levels. Conclusions. The Brazilian Standards establishes 50dB(A) and 70dB(A) as the maximum limits for environmental noise in residential and industrial areas, respectively. The results of this study indicate that the problem of urban noise in the city of Sao Paulo needs to be tackled urgently due to its important public health impact.



How to cite this article:
Moura-de-Sousa C, Alves Cardoso MR. Urban noise in the City of Sao Paulo, Brazil : An important problem of public health.Noise Health 2002;4:57-63


How to cite this URL:
Moura-de-Sousa C, Alves Cardoso MR. Urban noise in the City of Sao Paulo, Brazil : An important problem of public health. Noise Health [serial online] 2002 [cited 2022 May 22 ];4:57-63
Available from: https://www.noiseandhealth.org/text.asp?2002/4/16/57/31827


Full Text

 Introduction



The most known definition of noise is a sound undesirable and unpleasant that could result in injuries (Stanfield 1992). Thus, the perception of noise can be different depending on the listener and their interests; a music, for example, is a kind of a pleasant noise, while the noise of a sawmill is not.

Common sources of noise are, in general, (a) movement noise (urban, railway, air), (b) industrial noise, (c) noise from the buildings, and (d) noise from speaking and household appliances (Cremonesi 1984).

In large cities the main source of noise is the vehicle traffic which is frequently characterised by traffic jams. The great number of motor vehicles, with many of them in bad conditions; disrespect for traffic laws; loud noises from horns, alarms, and friction of tyres on imperfect road surfaces produce an uncomfortable environment and make life quality significantly worse (Granados 1998). A flat in such an urban area may be 30 dB(A) noisier than a similar one which is located in a rural area (Sho 1999).

In Brazil, the investment in the road system, as a stimulus for the new national motor vehicle industry in the 1950's, resulted in an enormous increase in the number of vehicles in circulation throughout the cities. The city of Sao Paulo, which is the centre of the most influential metropolitan area of the country, has now a vehicle fleet of more than 5 million units (CETESB 1999; Moraes 2000). Atmospheric and noise pollution related to vehicle traffic is thus some of the most serious environmental problems faced by the city in these days (Oppido and Latterman 1975).

Although regulations on environmental noise in Sao Paulo date back to the 1860s, the municipality, recognizing that noise-related problems are a matter of concern in the city, published a more specific law that defines the acceptable levels of noise and the procedures for assessing the sound pressure levels [City of Sao Paulo Environmental Law, law no. 11804, 19th June 1995 (Sao Paulo 2000a)].

Little is known, however, about the current levels of noise in the streets of this city. Thus, in this paper we present the preliminary results of a study conducted in Sao Paulo with the objective of estimating the levels of noise in roads with either heavy traffic or local traffic and comparing the data obtained with the thresholds established by the City of Sao Paulo Environmental Law.

 Method



Study Points

The points selected for the assessment of sound pressure levels were distributed around the city of Sao Paulo. They were located at any position along the length of urban roads with different characteristics such as width, type of surface, height of the buildings, presence of trees, and type of building use (residential or commercial). The roads were classified into two categories according to the traffic flow: a) heavy traffic and b) local traffic. A total of 17 points in roads with heavy traffic and 11 points in roads with local traffic were evaluated. [Figure 1] shows the geographical distribution of these points on a map of the city.

Data collection

The evaluation of each point was made using a 2236 Mediator from Bruel & Kjaer (type 1), with wind protector, acoustic calibrator and tripod. The noise data collection was based on the procedures established by the International Standard (ref. no. 1996/1982 1,2,3) - Acoustics - Description and Measurement of Environmental Noise (ISO 1996/1).

The calibration of the sound level meter was in accordance with the manufacturer's instructions. Recalibration of this instrument has been performed annually. In addition, in this study, after 6 hours of use of the Mediator, the microphone was checked.

All the measurements were performed at least 3.5 meters from any reflection structure and preferably at 1.2 to 1.5 meter above the ground. Finally, outdoor measurements near buildings were made at 1 to 2 meters from their front face. No measurement was made in the presence of meteorological events such as rain and thunder.

Sound pressure levels in the points located in roads with heavy traffic were measured during 2 minutes, while the measurement in those points with local traffic lasted 1 minute. The reason for this was the presence of traffic lights in the areas with heavy traffic which may influence the traffic flow. Thus, the different duration of evaluation allowed us to cover the representative noise events properly.

The points were evaluated from Monday to Friday during working time (8am to 5pm). The final number of measurements for each point was defined during the data collection. The standard error of the measurements was calculated periodically and new samples were added until the standard error was lower than 1 dB, the standard error of the Mediator.

Data analysis

The data obtained with the Mediator as equivalent continuous A-weighted sound pressure level (Leq), maximum mean sound pressure level (MaxL), and minimum mean sound pressure level (MinL) were 1- or 2-minute averages in decibel scale and A-weighted (which takes into account the human hearing frequencies) while the maximum peak sound pressure level (MaxP) was 1- or 2-minute average in decibel scale and C-weighted (which takes into account all the frequencies used).

All the data were entered into a computer using the STATA programme, version 6.0. The data file was then checked for completeness and for any potential errors.

The mean, the standard error and a 95% confidence interval - 95%CI were calculated for each point and also for the groups of points with heavy traffic and with local traffic, separately.

The confidence interval was calculated using the formula below:

[INLINE:1]

where:

x = TWA mean (decibels) of the sample distribution

t = distribution of t value with (n - 1) degrees of freedom and a confidence level (1 - α)

n = number of samples

σ = distribution standard deviation

The City of Sao Paulo Environmental Law (law no. 11804, 19th June 1995) establishes, in its 2nd article, that the noise which is higher than the thresholds defined by the Brazilian Registrated Rule - NBR 10151 of the Brazilian Standards (ABNT) may be hazardous to health and public peacefulness. This standard establishes the criteria for evaluation of outdoor environment, in dB(A), as shown in [Table 1], and determines that local authorities are responsible for defining the day and night periods in accordance with their population habits. For Sao Paulo, the law no. 11804 defined these periods as day between 6am and 8pm and night between 8pm and 6am (Brasil 2000; Sao Paulo 2000a).

Thus, in this study, we compared the sound pressure levels obtained in the city with the thresholds established for the day time.

 Results



The number of measurements for each point varied from 10 to 20. The equivalent continuous A-weighted sound pressure levels (Leq) obtained in urban roads with heavy traffic ranged from 70.88 to 80.18 dB(A), the maximum peak sound pressure levels (MaxP) from 102.47 to 108.37 dB(C), the maximum mean sound pressure levels (MaxL) from 83.54 to 91.38 dB(A), and the minimum mean sound pressure levels (MinL) ranged from 57.36 to 73.07 dB(A).

On the other hand, for the urban roads with local traffic the Leq obtained ranged from 50.82 to 66.88 dB(A), the MaxP from 83.13 to 97.33 dB(C), the MaxL from 61.41 to 78.68 dB(A), and the MinL ranged from 45.46 to 55.75 dB(A). There was a strong evidence in favour of the difference between the two types of traffic roads regarding the sound pressure levels (p<0,001). [Table 2] shows the data obtained according to the type of road, with heavy traffic or with local traffic.

[Table 3] presents the equivalent continuous A­-weighted sound pressure levels for each point measured. These points were divided into three different areas, defined by the Brazilian Standard (NBR 10151), with the respective limits of noise allowed.

 Discussion



High levels of sound pressure were observed in the city of Sao Paulo. For roads with heavy traffic, the mean sound pressure level surpassed even the higher accepted threshold established by the ABNT [70 dB(A) for industrial areas]. The mean sound pressure level for roads with local traffic was also high, being above the acceptable for residential and commercial areas. When the roads were classified according to the type of area using the NBR 10151 criteria, the points measured were all above the thresholds accepted for the respective area.

Some areas of the city, particularly the north and south areas, have not been covered in this survey yet. However, since the points measured were selected to represent the most common types of roads in the city, it is expected that the picture will not be different when more measurements are performed.

The noise can damage human health depending on its intensity, frequency and duration of exposure, as well as the individual susceptibility. The disorders may be auditory or extra auditory.

Pimentel-Souza and Alvares (2000) note that a noise up to 50 dB(A) may be annoying, but one can be adapted to the situation. A 55 dB(A) noise causes a light stress, excitement, dependence and discomfort and a 65dB(A) noise causes a deep stress. At a 80 dB(A) level of noise, the organism is likely to release biological morphine into the body, resulting in a feeling of pleasure that may lead to a type of dependence. At a 100 dB(A) it is possible to have an irreversible hearing loss.

The hearing effects of a noise that is intense enough are noise-induced permanent threshold shift, noise-induced temporary threshold shift, and acoustic trauma. Usually, these effects are accompanied by tinnitus (Russo and Santos 1993; Sanchez et al 1999).

The common extra hearing effects are cardiovascular effects, endocrine effects, physical disorders, mental and emotional difficulties like irritability, fatigue, stress, and social difficulties at work and at home, which lower life quality standards. In schools, one can observe difficulty in the speech communication when the outdoor noise is higher than the school noise. Teachers may have disphony and should make a hard effort during the speech. Students may have a reduction in creativity, troubles for being decision makers, in processing information, and also a deficit in attention (Marone 1969a; Marone 1969b; WHO 1995; Sho 1999).

The urban noise, or environmental noise pollution, however, is not a recent phenomenon. A poem of 1350 complaints about the noise made by blacksmiths and references to noises from the London streets dates back to the 1800s (Anthrop 1973).

In the city of Sao Paulo, the urban noise complaints are becoming more frequent. An important local newspaper has recently been publishing letters of complaint about noise problems very frequently. The complaints of the population are, in general, concerning with sleeping difficulties. However, no answer from the authorities has been given to these letters.

There is a programme in the city of Sao Paulo, called Urban Silence Programme, that has the objective of controlling the noise levels in this city, protecting the population well-being by preventing noise pollution. However, this programme deals only with excessive noise produced by business activities such as night clubs and bars that disturb the peace of the neighbourhood (Sao Paulo 2000b; Sao Paulo 2000c).

This study shows that the noise from the vehicle traffic is important and should be treated as a public health problem.[22]

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