Environmental Health in Australia and New Zealand:
Case Studies in Environmental Health Risk Assessment
N.J. CROMAR, J.S. HEYWORTH & J.P. RALPH
Case Study 7: Atmospheric Pollution in an Urban Setting
Tutor Notes and Teaching Aids
Introduction
This case study introduces the student to the process of assessing and managing public and
environmental health risks in an urban setting. The exercise presents a hypothetical scenario
in which members of an urban community have complained that their health is being
adversely affected by industrial noise and atmospheric pollution. The task of the student is to
develop a research methodology that investigates this concern. Specifically the methodology
should seek to address the following questions:
1.
2.
3.
Are residents exhibiting excessively high levels of respiratory health problems?
Are ambient levels of air and noise pollution excessive?
Could emissions from local industry be contributing to local health problems?
The research methodology should also include the participation of the local community.
Learning Objectives
Upon completion of this case study, students will:
1.
2.
3.
4.
5.
6.
7.
8.
9.
be able to propose methods to investigate the health status of a defined
population;
be able to cite sources of information which are relevant to determining the
health status of a population;
be aware of associations between health, particularly respiratory health, and
industrial activities in urban environments;
to understand questionnaire design and validation for estimating the health
status, environmental exposure and risk behaviours of a population;
be able to identify the hazardous chemicals potentially emitted by selected
small industries;
be able to cite noise and air quality standards adopted by health and
environment authorities in their region;
know the major sources and hazardous properties of common air pollutants;
be aware of the difficulties of ascribing health effects to air pollutants present
at very low levels in urban areas;
know and understand the components of the risk assessment protocol.
Tutor Notes
Most of the questions assigned to students are provided with suggested answers - the “tutor
notes”. These answers are intended as a guide only.
Scenario Part 1
The Council of Urbanite is a local council in Hadley, a capital city with a population of about
1.4 million people. Urbanite is 10km from the central business district of Hadley. It occupies
an area of about 9km2, has a population of about 110,000 people and comprises six suburbs
that are almost exclusively residential. An exception is the suburb of Eldon that contains
residential dwellings as well as some factories and industries. A representative of the Eldon
Environment Action Group (EEAG) has brought to the attention of the Urbanite Council, the
State Health Department, the Environment Protection Authority (EPA) and the local Member
of Parliament the dissatisfaction of some residents with the environmental and public health
status of Eldon. These residents complained to the EEAG that their health is suffering from
exposure to industrial noise and to chemicals in industry emissions. These emissions, they
claim They claim are causing and aggravating respiratory problems including asthma and
bronchitis, and the noise levels are interfering with daily activities and disturbing sleep. You
are an environmental health officer, working for the Council of Urbanite, given the task of
investigating these claims and recommending appropriate action.
Note: All of the information, that you require to fully investigate these claims, may not be
made available. You will need to work within the confines dictated by the data given. This is
intended to model the limitations experienced in real life in which all desired information may
not be available for reasons such as, economy, time and available technology.
Tasks
1.1
List the information that you already have and also that you think should be
obtained as part of an investigation.
1.2
From where might this information be obtained?
1.3
Review the literature to determine if emissions from industries in urban
environments in other parts of the world have been associated with acute and
chronic respiratory health effects. What industries and what air pollutants have
been associated with respiratory conditions?
1.4.
What are the hypotheses?
1.5
Start to discuss ways in which these hypotheses might be tested.
1.6
How might you involve the community at this stage?
Tutor Guide
A1.1
Before attempting to identify an association between industry emissions and
public health in Eldon the following questions should be addressed:
What specific health problems are the community concerned
about?
What industries exist in this area?
What is the composition of the population?
Is there any data that indicates that there are potentially
elevated levels of specific health problems within the resident
population of Eldon?
How long have these problems existed?
What are the levels of noise and atmospheric pollution in
Eldon and are they sufficiently high to be potentially
hazardous to public health?
If there are elevated levels of specific health problems in
Eldon, what are the potential confounding risk factors for these
effects i.e. risk factors for these effects which are unrelated to
industry activities (e.g. smoking, indoor sources of air
pollution)?
A1.2
From the representative of the EEAG the following information might be
obtained:
 the history of the EEAG, the reasons for its formation and the mechanisms
which residents use to convey their complaints to the governing body;
 the number of people who claim that their health is suffering due to industry
activity;
 demographic information about these individuals e.g. their age, sex, duration of
residence in Eldon, nature and location of employment, health history and
personal habits. Demographic and health information about individuals who
live close to complainants but who have not indicated that their health is
affected by local industry should also be obtained;
 the ndustries in Eldon, their location and proximity to the homes of
complainants. If the EEAG have researched the activities of local industries
they may also be aware of the industrial processes involved, including the
chemicals consumed and produced by these processes, and the types of
emission controls which are used.
Some of this information might be obtained from Urbanite Council records, from
the State Health Commision and from the ABS. It may also be necessary to
survey residents and industries of Eldon directly.
Local general practitioners may be able to provide details of:
(i)
particular health effects which have been reported with unusually high
frequency;
(ii)
the nature of these health effects;
(iii)
probable causes of these health effects.
The responses of these GP’s should be compared with the responses of other GP’s
who service areas outside of Eldon and to health statistics released by the State Health
Commission and the ABS.
The Urbanite City Council, the State Health Commission and the EPA may have
information about the industries in Eldon which have a history of poor environmental
and public health safety including accidents, spillages and inadequate control of
chemical emissions and noise.
The EPA or the Department of Environment and Natural Resources may have
installed air pollution monitoring stations near Eldon. If so, information about the air
pollutants that were measured, the levels of these contaminants in recent years, the
maximum permissible levels adopted by a relevant authority (e.g. NH&MRC) and the
health effects associated with high levels of these atmospheric contaminants will be
available.
Students should be made aware of the differences between actual and perceived risk.
Although the health of some of the residents of Eldon may be impaired due to
emissions from one or more of the local industries, other residents of Eldon may
perceive incorrectly that their health is being affected by these industries. Such a belief
may arise as a result of the high unaesthetic profile presented by the factories (e.g. the
large size of the buildings, the tall chimneys on their roofs, the smoke, noise and
odours they produce) coupled with a perception that industrial noise and effluent is
inherently unhealthy. Thus, supporting evidence is required.
A1.3
References which are relevant to this task include the following:
Abramson, M. and Voigt, T. (1991) Ambient air pollution and respiratory disease. Med.
J. Aust., 154: 543-53.
Bhopal, R.S., Moffatt, S., Pless-Mulloli, T., and Phillimore, PR. (1998) Does living
near a constellation of petrochemical, steel, and other industries impair health? Occup.
and Environ. Medicine. 55: 812-822.
Christie, D., Spencer, L. and Senthilselvan, A. (1992) Air quality and respiratory
disease in Newcastle, New South Wales. Med. J. Aust. 156: 841-844.
Cole, D.C., Tarusk, V., Frank, J.W. and Eyles, J. (1996) Research responses to
outbreaks of concern about local environments. Arch. Environ. Health, 51: 352-358.
Dales, R.E., Spitzer, W.D., Suissa, S., Schechter, M.T., Tousignant, P. and Steinmetz,
N. (1989) Respiratory health of a population living downwind from natural gas
refineries. Am. Rev. Resp. Dis. 139: 595-600.
Dockery, D.W., Speizer, F.E., Stram, D.O., Ware, J.H., Spengler, J.D. and Ferris, B.G.
(1989) Effects of inhalable particles on respiratory health of children. Am. Rev. Resp.
Dis. 139: 587-594.
Graber, D.R. and Aldrich, T.E. (1993) Working with community organisations to
evaluate potential disease clusters. Soc. Sci. Med., 37: 1079-85.
Lipscomb, J.A., Satin K.P. and Neutra, R.R. (1992) Reported symptom prevalence rates
from comparison populations in community-based environmental studies. Arch.
Environ. Health. 47: 263-269.
Singleton, C.D., Gatrell, A.C. and Briggs, J. (1995) Prevalence of asthma in primary
school children in an industrial part of England. J. Epidemiol., 49: 326-327
Strachan, D.P. (1992) Causes and control of chronic respiratory disease: looking beyond
the smoke screen. J. Epidemiol. Comm. Health, 26: 177-179
Wilkie, A.T., Ford, R.P., Pattermore, P., Schluter, P.J., Town, I. and Graham, P. (1995)
Prevalence of childhood asthma symptoms in an industrial suburb of Christchurch. New
Zealand Med. J., 108: 188-190.
Wjst, M., Reitmoor, P., Dold, S., Wulff, A., Nicolai, T., Loeffelholz-Colberg, E. and
von Mutius, E. (1993) Road trafic and adverse health effects in children. BMJ, 307:
596-599.
In summary, a variety of industry processes, mostly involving combustion and other
high temperature operations, and waste dispositories have been associated with
respiratory illness in nearby communities.
A1.4 Students need to bear in mind that they are dealing with a “real” human population and
that, in consequence, there will be limitations on the investigative procedures which can
be employed in this study. Firstly, for practical and ethical reasons, experimentation is
unlikely to be an option. It is not reasonable to propose that residents and industries
participate in a study in which they are excessively manipulated e.g. in which residents
are housed closer to or further from selected industries or in which industry practices are
changed in order to observe the effect of these changes on public health. Therefore,
since the study population (the residents of Eldon) and the putative risk factors
(industrial air pollutants) cannot be sufficiently controlled by the investigator (the
student) the study will need to be observational rather than experimental.
Secondly, the investigation should be completed within a reasonable time frame. The
residents of Eldon, and the EEAG in particular, can be expected to want to know if
industrial emissions are likely to be affecting their health as soon as possible. Therefore,
a longitudinal observational study such as a cohort study can be disregarded for the
present. However, students should be aware that the impact of air pollution on public
health might be more effectively assessed if the study limitations discussed here were
not in place.
Thirdly, since individuals with particular respiratory complaints have not yet been
identified in Eldon it is not possible to investigate a case-control study. Such a study
might be warranted in the future if it can be shown that there is an unexplained elevated
prevalence of respiratory conditions in Eldon.
In conclusion, it is recommended that the students consider planning a cross-sectional
(sometimes called a non-directional) observational study to assess the prevalence of
respiratory conditions in Eldon. Data could be gathered relatively quickly, cheaply and
in an ethically feasible fashion by implementing a survey. If the residents of Eldon only
are included in the survey then the results will be descriptive and may not allow the
community diagnosis to be associated with industrial emissions. However, the study can
be refined by comparing the health status of the Eldon community with the health status
of a control group which does not have the same level (and preferably a considerably
different level) of exposure to emissions from the types of industries operating in Eldon
but is otherwise closely matched to the Eldon community. Such a study would be
analytic.
A1.5 Students will find it helpful to examine validated questionnaires such as the National
Health Surveys which are used by the ABS and to consult texts on research methods in
community health e.g. Leeder (1988) and Abramson (1990). Students should be clear
about the objectives of their survey.
Demographic information which might be sought in the questionnaire includes: age (or
age grouping), gender, period of residency in Eldon and mean daily time spent in Eldon.
To assess the impact of health risks unrelated to industry, information might be sought
about the respondent’s occupation, home environment (particularly indoor sources of air
pollutants such as cooking and heating appliances, floor coverings, pets) and smoking
habits including passive smoking.
To assess the health status of respondents they could be asked to specify the frequency
of particular health effects e.g. sore throat, headache, irritated eyes, shortness of breath,
wheezing breath and coughing.
To assess the respondent’s perceptions of their residential environment and the possible
effects of industry emissions they could be asked their opinion on: ambient air quality
(e.g. odour, visibility), noise levels and perceived sources of ambient noise and air
pollution. Respondents might also be asked if they have had to take action to counter or
minimise the effects of noise or air pollution e.g. shut windows and vacate the home.
Some factors to be considered when implementing a survey by mail, telephone and
personal interview are described briefly here (adapted from Davies and Kempnich
1991).
(a)
(b)
(c)

Mail survey: cheap, requires addresses of participants, response rate is often
low, questions must be simple and cannot be clarified after the mail-out,
participants must be literate, length of questionnaire should not be daunting.
Telephone survey: relatively cheap and time-consuming, participants must
have a phone, should not take excessive amount of time, it is possible to clarify
questions and answers during the interview.
Personal interview: time consuming and expensive, interviewer must have
transport, high response rate, immediate feedback allows questions and
answers to be clarified, amplified and modified during the interview.
Should we include a survey as an example? If so, we may need permission from the
source.
A1.6
If the entire Eldon community is not going to be included in the survey it is important
that a subset of the community be selected randomly i.e. without bias towards or from
a specific group of individuals. Thus, people who have complained that industry
emissions are affecting their health should not automatically be included in the survey.
Nor should individuals be permitted to volunteer themselves for inclusion in the
survey because people who have a complaint about air pollution might be more
inclined that people with no complaint to be involved in the study. A simple and
effective method of randomly choosing a group of Eldon households is to note all of
the home addresses in the study community and then to blindly pick these addresses,
one by one, until the desired number of participating households is reached. Therefore,
participants can literally be picked “out of a hat” although more sophisticated
methods, such as the use of random number generator, can be used. Note that an
element of bias in the study may be unavoidable if households which have been
selected then choose not to take part in the survey.
Ideally, the control group would:
(a) be of a similar size to the Eldon group and occupy a similar geographical area;
(b) be located relatively close to Eldon and preferably upwind;
(c) reside in a non-industrial area;
(d) have comparable cross-sectional socioeconomic, age, racial, employment and
other relevant structures.
Scenario Part 2
The EEAG have provided you with the following information:
The EEAG was formed approximately 2 years ago by residents of Eldon who are concerned
about the presence of industries near their homes, the possible health effects of exposure to
factory exhausts which are visible and/or evident by their smell and the noise produced by a
timber yard. The EEAG meets monthly and, at the first meeting, several residents expressed
their belief that some of their respiratory health problems were the result of industrial activity
close to their homes. Last year the EEAG surveyed that portion of the Eldon community
which resides within 100 metres of an industrial site. This information is summarised here.
All residents of Eldon who have attended meetings of the EEAG live within a region bounded
by the Main North, South and West Arterial Roads and by a railway line to the east. (Figure
1). There are 138 homes in this region housing an estimated population of 485 people. The
industries within this region are a timber yard, a paint manufacturer, a motor vehicle spray
painter, an electroplater and a dry cleaner (Figure 1). There are no other major industries
within 1km of this region. Complaints of excessive noise, all directed at the timber yard, have
been lodged with the EEAG by 13 households. Each of these households is situated within 50
metres of the timber yard. The occupants of 43 homes have registered complaints of localised
air pollution with the EEAG. Some residents are also unhappy with the appearance of the
stack that vents the combustion chamber in which saw dust and wood scraps are burnt at the
timber yard.
Main North Arterial Road
xSt.
x x
Jo
x x xhn
x Ba x x
nk
sia
Ro
x ad
Ma
in
W
est
Art
eri
al
Ro
ad
x
St.
x
Joa
x x x n
x
Gumdrop Avenue
A
x x x
B
x x
xAs
x
h
St.
x
x x x Gr
Wattle Street
D
C
x x
ee
n
Str
eet
E
x
x
x
x
x x
Acacia Avenue
x
Bl
x
x
xW
hit
ue
x e
St.
Rd
.
Main South Arterial Road
Re
d
St.
x
x
x
Key
Railway line
A Timber yard
Fence lines
E
B
Paint manufacturer
C
Spray painter
D Electroplater
50 m
N
Dry cleaner
Households which have
complained about:
x; air pollution.
x ; air and noise pollution.
Figure 1. Locations of industries in Eldon
The EEAG surveyed 260 people from 74 of the homes shown in Figure 1 and 286 people
from 72 homes in Burly, a residential-only suburb located 5km south of Eldon. Homes were
randomly selected and all of the households in Eldon which have complained of industryrelated health effects may not have been surveyed. A summary of their findings is given here.
Residents were categorised into 10-year age groups with the exception that individuals 14
years old and under were placed within a single age group. The sex and prevalence of
smokers was recorded (Table 1). To estimate the health status of each community the
prevalence of respiratory conditions (bronchitis/emphysema, asthma, persistent cough and
sore throat) and non-specific health effects (headache, arthritis) were determined (Table 2).
Table 1. Demographics and prevalence of smokers in the Eldon and Burly survey
populations.
Age group
Number of
Gendre
Number of current
(years):
residents
Males
Females
smokers
E
B
E
B
E
B
E
B
0-14
57
52
30
29
27
33
nd
nd
15-24
42
41
19
20
23
21
17a
14a
25-34
43
55
21
25
22
30
16
14
35-44
39
51
19
28
20
23
13
9
45-54
28
42
12
16
16
16
8
8
55-64
23
18
12
9
11
9
6
7
65-74
19
11
8
7
11
4
4
6
> 74
9
16
3
7
6
9
3
6
Total:
260
286
124
141
136
145
67
64
E: Eldon; B: Burly.
nd: not determined.
a
Data applies to individuals in 18-24 years age group only.
Table 2. Symptom prevalence in the Eldon and Burly survey populations.
Age
grouping
(years)
0-14
15-24
25-34
35-44
45-54
55-64
65-74
> 74
Total:
Long-term health conditiona
asthma
cough or sore
headacheb
throat
E
B
E
B
E
B
12
7
1
0
0
1
8
5
0
0
1
0
5
5
0
1
0
0
4
1
1
0
0
0
4
5
1
1
1
2
3
3
0
0
1
1
3
1
1
1
0
1
1
1
0
0
1
1
40
28
4
3
4
6
Bronchitis/
arthritis
emphysema
E
B
E
B
2
0
0
0
2
1
1
0
2
0
1
1
3
2
3
4
2
2
5
8
3
1
6
4
3
1
7
5
2
1
4
5
19
8
27
27
E: Eldon; B: Burly.
(a) The condition is current and has lasted for not less than 6 months. The complaint usually
occurs at least once per week.
(b) Not attributed to stress or tension
Tasks
2.1
Does the Burly community provide a suitable control group for the Eldon community?
Specify the characteristics of the Burly community which make it either acceptable or
unacceptable as a control group for Eldon?
2.2
How does the prevalence of smokers in Eldon compare with the prevalence of smokers
in Burly and in your own State? What other information concerning smokers may be
useful?
2.3
How do the levels of respiratory conditions, headache and arthritis in Eldon compare
with these levels in Burly and in your own State? Why might the prevalence of arthritis
have been determined given that this condition is unlikely to be affected by urban air
quality?
2.4
Does this data confirm that air pollution from industries in Eldon may be causing or
aggravating respiratory diseases? What further information would you seek to better
estimate the health status of Eldon residents and the prevalence of behavioural,
domestic and environmental determinants of health effects?
2.5
What chemicals might be emitted by each of the industries in Eldon?
Tutor Guide
A2.1 For ease of comparison each datum in Table 1 can be expressed as a percentage of the
number of individuals surveyed in each community (see Table T1).
The age and gender structure and prevalence of smokers in Eldon and Burly are similar.
These similarities and the absence of industries in Burly suggests that Burly is a suitable
control community for the Eldon group. However, the higher prevalence of smokers
over 14 in Eldon may be sufficient to measurably influence the prevalence of
respiratory complaints and should be considered when making associations between
health effects and risk factors. Furthermore, other features of community structure (e.g.
socioeconomic status, ethnicity, employment, quality of home environment) which may
impact on respiratory health have not been assessed and the absence of this information
means that conclusions about risk factors must be made with caution.
Table T1. Demographics and prevalence of smokers in the Eldon and Burly survey
populations (% of total population, to the nearest whole numbera)
Age group
(years):
Residents
Gender
Current smokers
Males
Females
E
B
E
B
E
B
E
0-14
22
18
12
10
10
12
nd
15-24
16
14
7
7
9
7
7
25-34
17
19
8
9
8
10
6
35-44
15
18
7
10
8
8
5
45-54
11
15
5
6
6
6
3
55-64
9
6
5
3
4
3
2
65-74
7
4
3
2
4
1
2
> 74
3
6
1
2
2
3
1
Total:
100
100
48
49
51
50
33b
a
The sum of a column and the total in that column may differ due to rounding.
B
nd
5
5
3
3
2
2
2
27b
b
The percentage of smokers in the population not including individuals in the 0-14 years
age group.
A2.2
The proportion of individuals over 14 years who smoke in Eldon (33%) is marginally
greater than the proportion of individuals over 14 years who smoke in Burly (27%),
due to the higher prevalence of smokers in Eldon between 14 and 45 years (Table T1).
Information on the prevalence of smoking in your region might be published by the
Regional Health Commission.
Example: Pilotto et al (1999).
Other potentially relevant data would be the number of smokers, ex-smokers, passive
and non-smokers per household, the total period over which individuals have smoked,
the tar strength of the tobacco used and the prevalence of smokers within each gender.
A2.3
Some students may choose to express the prevalence of long-term health conditions as
a percentage of the total sample population as shown in Table T2.
However, it should be noted that the data in Table T2 does not allow easy comparison
of the prevalence of a health condition in a given age group in Eldon with its
counterpart in Burly because, when the prevalence is expressed as a percentage of the
total sample population, the number of individuals in each age group (with and
without a health condition) is ignored. The data in Table T2 does, however, allow for
easy estimation of the contribution of each age group to the total prevalence of each
condition. For example, it can be seen that no single age group in Eldon and Burly
makes a notably larger or smaller contribution of bronchitis/emphysema, cough/sore
throat, headache or arthritis and that individuals under 25 years old represent about
half of all asthma sufferers in Eldon. The data also allows easy comparison of the
prevalence of each condition between Eldon and Burly. For example, the percentage
prevalence of bronchitis/emphysema and asthma is about 2.5 times higher and 1.5
times higher, respectively, than the percentage prevalence of these conditions in Burly.
Table T2. Symptom prevalence in the Eldon and Burly survey populations (% of total
population rounded to second decimal placea).
Age
Long-term health condition
grouping
bronchitis/
asthma
cough or sore
headacheb
arthritis
(years)
emphysema
throat
E
B
E
B
E
B
E
B
E
B
0-14
0.77
0
4.62
2.45
0.38
0
0
0.35
0
0
15-24
0.77
0.35
3.08
1.75
0
0
0.38
0
0.38
0
25-34
0.77
0
1.92
1.75
0
0.35
0
0
0.38
0.35
35-44
1.15
0.70
1.54
0.35
0.38
0
0
0
1.15
1.40
45-54
0.77
0.70
1.54
1.75
0.38
0.35
0.38
0.70
1.92
2.80
55-64
1.15
0.35
1.15
1.05
0
0
0.38
0.35
2.31
1.40
65-74
1.15
0.35
1.15
0.35
0.38
0.35
0
0.35
2.69
1.75
> 74
0.77
0.35
0.38
0.35
0
0
0.38
0.35
1.54
1.75
Total:
7.30
2.80 15.38
9.80
1.52
1.05
1.52
2.10 10.37
9.45
a
The sum of a column and the total may differ due to rounding.
Students should be made aware that calculating the percentage of individuals with a
health condition in each age group is an appropriate comparison of the prevalence of
age-specific health conditions in Eldon with those in Burly (Table T3).
Table T3. Symptom prevalence in the Eldon and Burly survey populations (% of total in
each age group)
Age
grouping
(years)
0-14
15-24
25-34
35-44
45-54
55-64
65-74
> 74
Mean %
bronchitis/
emphysema
E
B
3.5
0.0
4.8
2.4
4.7
0.0
7.7
3.9
7.1
4.8
13.0
5.6
15.8
9.1
22.2
6.3
9.9
4.0
asthma
E
21.1
19.1
11.6
10.3
14.3
13.0
15.8
11.1
14.5
B
13.4
12.2
9.1
2.0
11.9
16.7
9.1
6.3
10.1
cough or sore
throat
E
B
1.8
0.0
0.0
0.0
0.0
1.8
2.6
0.0
3.6
2.4
0.0
0.0
5.3
9.1
0.0
0.0
1.7
1.7
headache
E
0.0
2.4
0.0
0.0
3.6
4.4
0.0
11.1
2.7
B
1.9
0.0
0.0
0.0
4.8
5.6
9.1
6.3
3.5
arthritis
E
0.0
2.4
2.3
7.7
17.9
26.1
36.8
44.4
17.2
B
0.0
0.0
1.8
7.8
19.0
22.2
45.4
31.3
15.9
Higher levels of bronchitis/emphysema and asthma were reported in Eldon than in
Burly within all age groups except that Burly has a higher prevalence of asthma
sufferers in the 55-64 age group. There are no notable differences between the
prevalence of cough/sore throat, headache or arthritis in Eldon and Burly. Arthritis
serves as a useful indicator for comparing the non-respiratory health of the Eldon and
Burly populations. Arthritis, a non-respiratory disease unlikely to be influenced by air
quality, is present essentially equally in Eldon and Burly and supports the assertion that
elevated levels of respiratory complaints in Eldon are due to local determinants.
Headache, although it also is a non-respiratory complaint, can be expected to be
aggravated by poor air quality. However, the prevalence of both headache and
cough/sore throat are low and the measured differences between their levels in Eldon
and Burly must be treated cautiously. Large changes in the percent prevalence of these
conditions in Eldon are dependent on only small changes in the absolute number of
individuals (as low as one person) who have these conditions. For example, only one
Eldon resident over 74 years old complained of recurring headache but, because the
total number of people in the survey who were over 74 years is small (nine, see Table
1), headache is reported to be experienced by over 11 % of people in this age group.
Note also that the levels of health conditions in Eldon will vary as individuals move into
and out of the area. If individuals with respiratory problems had left Eldon prior to the
health survey then the prevalence of some respiratory conditions may have been higher
in the past.
Thus, there is an unaccountable difference in the prevalence of some respiratory
conditions between the two communities and it is tempting to conclude that the poorer
state of respiratory health in Eldon is due to local risk factors such as industrial air
pollution. However, it would be useful to put the various health conditions in Eldon and
Burly into better perspective by examining their prevalence in the wider community.
This approach addresses the question: Are respiratory diseases more prevalent in Eldon
because there exist in Eldon risk determinants not present in Burly or because there
exist in Burly health “promoters” not present in Eldon? National health surveys provide
such useful comparative data (Table T4).
Table T4. National Australian age-specific prevalence of long-term health conditions in 1989-90
(%)
Age grouping
(years):
0-14
15-24
25-34
35-44
45-54
55-64
65-74
> 74
Mean percent
bronchitis/
emphysema
1.7
2.4
2.4
2.2
2.6
5.4
6.9
6.1
3.7
Long-term health condition
asthma
cough or sore
headache
throat
13.2
<1.0
<1.0
10.0
<1.0
<1.0
6.3
<1.0
<1.0
5.4
<1.0
<1.0
5.5
<1.0
<1.0
5.1
<1.0
<1.0
6.2
<1.0
<1.0
3.7
<1.0
<1.0
6.9
<1.0
<1.0
arthritis
<1a
1.64
3.91
7.77
16.09
28.49
37.58
41.72
17.15
a
Rounded to zero to calculate mean percent.
Source: ABS 1989-1990 National Health Survey
Although the prevalence of asthma is slightly higher in Burly than nationally the
prevalence of each of the other reported symptoms in Burly is about par with their
prevalence at the national level, further indicating that the Burly population is a valid
control for the Eldon population. The reported levels of bronchitis/emphysema and
asthma in Eldon are more than twice the national levels. In the over 74 age group the
prevalence of these conditions is almost four times the national levels.
In summary, the prevalence of bronchitis/emphysema and asthma in Eldon are higher
than in the nearby suburb of Burly and nationally. The data suggests that risk factors of
these diseases in Eldon be investigated further.
A2.4 The prevalence of respiratory disorders in Eldon is unexpectedly high but as yet this is
not evidence that air pollution from industries is responsible. It must be made clear to
students that, while there is an association between the presence of industries in Eldon
and the health of the populace, the data does not prove that industry is in any way
affecting public health other than causing the anxiety described in the introduction. An
excellent example of an epidemiological study which illustrates this point is provided by
Hocking et al. (1996) who report an association between health and proximity to TV
towers. The study is complemented by an editorial (Cartwright 1996) which further
clarifies the important differences between association and causation. We recommend
that students read these or similarly directed articles.
Further questions, the answers to which might permit a better assessment of the
determinants of respiratory health in Eldon, are:
1. How many of the reported health conditions were verified by medical
examination?
2. What is the prevalence of ex-smokers and passive smokers in Eldon?
3. What is the prevalence of respiratory conditions amongst smokers and exsmokers?
4. How many residents have conditions listed in Table 2 which pre-date their
residency in Eldon?
5. How does the prevalence of respiratory conditions relate to the residency time of
complainants in Eldon?
6. What are the recognised risk factors of asthma, bronchitis and emphysema? Are
these factors evident in Eldon?
7. Does the population of Eldon include disproportionately high fraction of
individuals who are genetically prone to health conditions listed in Table 2 (e.g.
race-related predisposition)?
A2.5
It is suggested that students investigate the work practices and chemical processes
used by local industries of the types shown in Figure 1. It is not possible to state the
specific chemicals used in, and which might be emitted by, these industries due to the
existence of alternative work practices and processes. However, it is probable that:
(a) the dry cleaner uses tetrachloroethylene;
(b) the paint manufacturer and spray painter use a variety of organic solvents
and polymers
(c) the electroplater uses acids, alkalis, fluxes and heavy metals
(d) the woodyard may use varnishes and stains dissolved in organic solvents.
Scenario Part 3
The Air Quality Branch of the EPA has an air pollution monitoring station in Eldon located
0.5km north of the joinery. The prevailing wind directions in Eldon are north, north-ease and
east. The monitor determines the atmospheric concentration of suspended particles, ozone,
nitrogen dioxide (NO2) and particulate lead. A summary of data recorded over the last ten
years is shown in Figure 2.
The EEAG measured noise levels in Gumdrop Avenue and Wattle Street. Residents in these
streets had complained of excessive noise generated by band saws and other wood-cutting
machines in the timber yard before 7:30am, and sometimes as early as 6:30am, on week-days.
Background noise levels (i.e. noise levels recorded when machinery in the timber yard was
not operating) were between 15 and 39 dB(A), expressed as the mean noise level over a 15
minute period. Noise levels recorded while cutting equipment was operating were between 29
and 52 dB(A). Over a one month period noise levels recorded before 7am were usually below
20 dB(A) but were as high as 42dB(A) on two occasions when cutting equipment in the
timber yard was used.
Total suspended particulates
(ug/m3)
100
90
80
70
60
50
40
30
20
10
0
10
9
8
7
6
5
4
3
Year (retrospectively)
2
1
Figure 2a. Ambient concentration (annual geometric mean) of total suspended particulates in Eldon.
0.16
0.14
Ozone (ppm)
0.12
0.1
0.08
0.06
0.04
0.02
0
82
83
84
85
86
87
Year
88
89
90
91
Figure 2b. Ambient concentration (one hour annual maximum) of ozone in Eldon
Nitrogen dioxide
(ppm)
0.2
0.18
0.16
0.14
0.12
82
83
84
85
86
87
Year
88
89
90
91
Figure 2c. Ambient concentration (one hour annual maxima) of nitrogen dioxide in Eldon
total suspended particulate
lead (ug/m3)
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1
82
83
84
85
86
87
Year
88
89
90
91
Figure 2d. Ambient concentration (annual geometric mean) of total suspended particulate lead in
Eldon.
Tasks
3.1
What are the national goals for ambient concentrations of particulates, ozone, nitrogen
dioxide (NO2) and particulate lead? If an Australian national goal has not been set, what is
the US ambient air quality standard?
3.2
Comment on the air quality in Eldon. What pollutants are present at levels of concern?
What are urban and industrial sources of suspended particulates, ozone, nitrogen dioxide
(NO2) and particulate lead?
3.3
List the respiratory disorders known to be caused or aggravated by each of the air
pollutants monitored in Eldon.
3.4
List other commonly occurring air pollutants associated with respiratory disease which
were not monitored in Eldon.
3.5
Comment on the likelihood that poor air quality in Eldon is due to emissions from local
industries and is responsible for respiratory problems.
3.6
What are the maximum permitted noise levels in urban residential areas? Do the noise
levels emitted by the timber yard exceed these maxima?
3.7
What would you advise be done about the noise problem in Eldon?
Tutor Guide
A3.1
There are currently (2002) no national Australian goal for ambient air concentrations of total
suspended particulates. The US ambient air quality standard for total suspended particulates
was 75 ug/m3 (annual geometric mean concentration). The NHMRC goal for total
suspended particulate lead was 1.5 g/m3 and for ozone was 0.12 ppm (one hour average).
The ANZECC goal for nitrogen dioxide was 0.16 ppm (one hour average).
A3.2
Sources of these air pollutants include transportation (primarily automobiles), coal- and oilfired electric power plants, industry, fossil fuel- and wood-based domestic heating, refuse
burning and to a lesser extent volcanoes, forest fires, dust storms and soil microbiota.
Particulate matter includes pollen, dust, soot and smoke. Particulate matter smaller than 10
micrometers in diameter is, upon inspiration, able to travel to the alveoli of the lungs where
it irritates alveolar tissue. Ozone, NO2, sulphur dioxide and carbon monoxide are also
respiratory irritants. Urban NO2 is formed predominantly by internal combustion engines
and power plants. Ozone is formed by reaction between NO2 and atmospheric hydrocarbons
(eg. unburnt petrol). Lead is present in the exhaust of motor vehicles that burn leaded petrol.
A3.3
Particulate matter smaller than 10 micrometers in diameter is, upon inspiration, able to
travel to the alveoli of the lungs where it irritates alveolar tissue. Ozone and NO2 are also
respiratory irritants.
A3.4
Sulphur dioxide and carbon monoxide.
A3.5 Eldon has, in recent years, shown relatively high concentrations of suspended particulates and
ozone. These pollutants may have caused the prevalence of respiratory problems to increase.
They are probably derived principally from road and rail transport, especially as there are at
least 3 major arterial roads and a railway line in Eldon. The timber yard, which burns saw dust
and wood, may also be a source of suspended particulates. However, respiratory irritants may
also have been released by the other industries in Eldon. These include organic solvents from
the dry cleaning company, the paint manufacturer and the spray painter. Organic solvents,
upon reaction with NO2, may constitute a local source of atmospheric ozone. Monitoring for
elevated levels of organics near the industries in Eldon is warranted.
A3.6 The Environment Protection (Industrial Noise) Policy 1994 has set the following noise
maxima:
Area in which noise source is situated
Maximum noise levels (dB[A])
7 am - 10 pm
10 pm - 7 am
Urban residential
52
45
Urban residential with some commerce, or with a 55
45
school, hospital or the like
Urban residential with some manufacturing industry 58
50
Noise emitted from non-domestic premises is excessive if the noise level at the measurement place
for a period during which noise is emitted from the premises (a) exceeds by more than 5dB(A) the background noise level at the measurement place; and
(b) exceeds the maximum noise level for that time of day and the area in which the premises
are situated.
Eldon is urban residential with some industry. Thus, the noise levels emitted by the timber yard do
not contravene the maximum levels dictated by the time of day and the area in which it is situated.
However, the timber yard is emitting excessive noise since it raises the noise level by more than 5
dB(A) above the background level. It would be useful to know the nature of the noise complaints
e.g. volume, tone, duration, time of occurrence (night, early morning).
A3.7
The operators of the timber yard need to be made aware of the excessive noise levels
emitted from the work place. Installing noise suppression equipment on the saws might
rectify the problem. The operators should be encouraged to defer operation of the saws until
at least after 7 am and as late as possible. The noise problem in Gumdrop Avenue is
probably compounded by traffic noise from the nearby Main North Arterial Road.
Scenario Part 4
Air at 10 roadside sites within the area depicted in Figure 1 was monitored for tetrachloroethylene,
petroleum ether and isocyanate (isocyanates contain the isocyanate -N=C=O functional group).
These compounds were collected onto absorbent filters from air samples which were taken at
ground level at a rate of 1 m3/sec for a period of one hour, twice a day for five days. The lowest
limit of detection for each compound was not more than 0.1 g. Only isocyanate was detected. The
mean concentration within all air samples was 2 g NCO/m3.
The EPA have not had prior cause to investigate any of the industries in the Eldon area. They have
received no complaints of poor work practices or of accidents involving hazardous chemicals. A
recent investigation of plant and equipment used by the dry cleaner, spray painter, electroplater and
paint manufacturer revealed no faults other than a leaky filter in the exhaust duct which ventilates a
spray painting cabinet.
Tasks
4.1 Which industries in Eldon might use tetrachloroethylene, petroleum ether and/or isocyanate?
4.2 What health hazards are associated with each of these chemicals?
4.3 Comment on the likelihood that isocyanate is a cause of respiratory conditions in Eldon.
Tutor Notes
A4.1 The dry cleaner may use tetrachloroethylene as a cleaning fluid. The spray painter and paint
manufacturer may use petroleum ether as a paint solvent and isocyanate as a component of
two-part polyurethane paints.
A4.2 The health hazards associated with these compounds are numerous and varied. They are
adequately described in most texts of the hazards of industrial chemicals.
A4.3
Organic isocyanates are irritants to skin, lungs, conjunctiva and gastrointestinal tract.
Respiratory sensitisation and asthma are caused by exposure to isocyanate. Symptoms in
sensitised individuals may become more severe with continued exposure over days to
months (Bruckner et al. 1968; Bolognesi et al. 2001). Since the mean atmospheric
concentration of isocyanate was 2 g NCO/m3 it is probable that peak levels of NCO and
levels of NCO recorded at some air sampling sites were significantly higher than 2 g
NCO/m3. The occupational exposure standards for isocyanates set by Worksafe Australia
are:
TWA (time weighted average): 20 g NCO/m3
STEL (short term exposure limit): 70 g NCO/m3
From the information given it is possible that atmospheric levels of isocyanates are causing
and aggravating respiratory conditions. The spray painting shop is a likely source of
atmospheric isocyanate.
Optional Assignment: Assessing the Risk
You should consider how you might assess the risk to public health from exposure to air in Eldon.
This process of risk assessment is typically divided into four discrete components:
1. Hazard identification: The process of determining whether an agent can cause an adverse health
condition.
2. Dose-response relationship: The relationship between the dose (amount and/or duration) of an
agent and the risk and severity of an adverse health condition.
3. Exposure assessment: The process of measuring or estimating the intensity, frequency and
duration of exposure to a hazardous agent.
4. Risk characterisation: The process of predicting the incidence of a health effect resulting from
exposure to a hazardous agent by combining the dose-response relationship with the exposure
assessment.
Conduct an assessment of the risk that Eldon residents will experience respiratory disorders as a
result of exposure to ozone, suspended particulates or isocyanates at the levels reported earlier.
Report all uncertainties in the data and the assumptions which you have made in order to
characterise the risk.
Tutor Notes
Risk assessment has been designated an optional topic because it is the primary focus of the other
case studies of this set. However, it is recommended that risk assessment be discussed here with
reference to the Eldon scenario to introduce to students the concept of estimating health risks.
The following questions may guide your discussion:
Hazard Identification
Does exposure to the agent affect human health?
Where is the agent found in the environment?
What types of adverse health effects have been reported?
What types of evidence exist that the agent is hazardous? e.g. human, animal or other studies.
Are any of the effects age-dependent or condition-dependent?
Does the agent exist in more than one form and, if so, is each form equally hazardous?
Exposure assessment
What exposure routes and levels are involved?
How is exposure measured?
How does the exposure relate to existing standards?
What are the occupational exposure standards defined by Worksafe Australia?
Estimate the daily uptake of the agent by the average adult and average child.
Are some groups exposed to higher levels of the agent than others?
Are there any other environmental, occupational and behavioural factors that may contribute to the
same adverse health effects?
Dose-response relationship
Has a dose-response relationship between exposure to the agent and the incidence of health effects
been determined? If so, what is this relationship?
Risk characterisation
What is the aggregate risk to public health within the Eldon population?
How does this health risk compare with others accepted by the community?
How much anxiety is the exposure causing?
Are there any categories of persons at particularly high risk because of their environmental
exposure circumstances or due to some inherent characteristics?
Scenario Part 5
Risk Management and Communication
You will need to decide if any reasonable action can be taken to improve the air quality in Eldon
with a view to reducing the risk of respiratory diseases. What strategies would you suggest and who
will need to be involved in your plans?
Furthermore, now that your investigation is complete, what will you tell the EEAG? Were the
residents correct in blaming local industries for their health problems? Do they have unexplained
poor health? Who and what else might be to blame for the resident’s problems?
Tutor Notes
The prevalence of respiratory problems in Eldon is unexpectedly high. There are a number of
risk factors which probably contribute to this situation:
(a) Suspended particulates released by the wood yard and vehicles;
(b) Isocyanates released by the spray painter and possibly the paint manufacturer;
(c) Ozone produced from vehicle exhaust.
(d) The number of people who smoke in Eldon.
Note that the level of each of the air pollutants that monitored in Eldon, when considered in
isolation of the other pollutants, is unlikely to account for all cases of respiratory disease.
Students should consider the possibility that synergy or potentiation exists between some
pollutants such that the risk of respiratory disease is magnified as a result of exposure to low
levels of more than one pollutant. There may also be other, as yet unknown, risk factors
operating in Eldon. The identity of these factors is a good topic for discussion. Students should
question the design of Eldon homes, the materials used for their construction and other domestic
factors which impact on the quality of indoor air (e.g. the type of heating appliances and floor
coverings used).
Students should recommend that the filtration devices which are used to prevent vapours and
particulates from escaping from spray painting booths be more vigorously maintained and more
frequently tested. The high volume of traffic in Eldon is cause for concern and residents might
lobby to have some traffic routes diverted around Eldon. Noise produced by the woodyard ought
to be easily managed. The saws could be operated later in the day and fitted with noise
suppression devices.