6
OCCUPATIONAL HYGIENE & ERGONOMICS
Physical and Chemical Hazards Exercises
Five questions.
Required: Maximum of 1000 words, excluding the original question, figures, tables. There is no need for references, but you can provide 1-3 if you like.
Question 1 (HEAT STRESS):
(3 marks)
He
icide spraying is taking place with a hand-held spray. The sprayers ca
y a container of weedkiller on their backs and the spraying covers a large area which they are covering on foot.
The sprayers have just come back from annual leave, this being their first week back.
To protect themselves against the he
icide, they are wearing cotton coveralls and gloves.
On the day when spraying is to take place, the temperatures are measured at 11am.
They are:
Globe temperature XXXXXXXXXX43.00C
Air temperature (dry bulb)
32.00C
Natural wet bulb temperature
20.00C
(i) Calculate the WBGT
(ii) If you were the supervisor of the sprayers, what work-rest program would you recommend, based on the WBGT above?
(iii) What work-rest program would you recommend for workers who had been back for two weeks?
Hints: Refer to pages 5- 7 of the Heat Stress notes
Is this light, moderate, heavy or very heavy work? What is the clothing co
ection?
(Image from sciencephoto.com)
Question 2 (HEAT STRESS):
(3 marks)
A young worker died of heat stroke when installing insulation in a roof space in Sydney in November 2009.
What factors might have contributed to the death?
Hint: think about “work, worker, workplace” issues.
(Image from http:
www.daviddarling.info/encyclopedia/I/AE_insulation.html)
Question 3 (NOISE):
(3 marks)
Preliminary remarks: Noise monitoring may be undertaken to assess health risk but it may also be undertaken to choose the right type of personal hearing protection. This question asks you to interpret noise exposure data, and suggest suitable protectors, in the context of the work actually being done. Note that, depending on the tasks, some workers might require different kinds of protection for the same overall noise level.
You are the health and safety adviser for a manufacturing company.
Suppose you have recently attended a noise training workshop. You become enthusiastic and decide to hire personal sound exposure meters to monitor workers for a 8 hr shift, so that there is a rational basis for the selection of personal hearing protectors.
You attach the meters to two workers, and they wear the meters for a full shift.
When the data from the meters are downloaded you obtain the average noise level and also the (highest) peak noise level.
Having done that, here are the results for the two workers:
Personal Sound Exposure Measurements:
LAeq, 8hr (dB)
Lpeak (dB C)
(average level)
(peak level)
Worker 1 (Fred)
89
107
Fred works in an area where the noise can be described as continuous low frequency noise. Most of the work just involves observation, and occasional adjustment of machinery.
89 dB(A) average and 107 dB(C) peak
Worker 2 (Joe)
91
130
Joe works in the assembly area where the noise can be described as intermittent “
oad band” noise. The work involves the use of adhesives, spray lu
icants, power tools and the occasional hammering.
91 dB(A) average and 130 dB (C) peak
What personal hearing protection would you recommend for each worker?
Justify your recommendations.
Hint: see NOISE NOTES PART3 page 15-16
Question 4 (LIGHTING):
(6 marks)
Preliminary remarks:
This is an exercise for you to do. You should try to analyse your own lighting environment, and then make recommendations for improvement.
It is important that you use a sketch or photo in your response.
Have a look at the lighting conditions in your work area (or if you are not working, your home study area).
Describe the type, state and orientation of the luminaires, the orientation of computer screens, the state of reflecting surfaces and the overall level of illumination. Is there natural as well as artificial light? Are there sources of glare? Briefly describe the a
angement, with a sketch or photos.
You might want to download a light meter (or lux meter) app for your smartphone and take some lux readings on your desk or “working plane”.
How you would improve the present circumstances?
Question 5 (CHEMICALS)
(5 marks)
Preliminary remarks:
This question assesses your understanding of health effects, labelling and exposure standards for ai
orne chemicals.
Background:
You are a health and safety consultant to a company manufacturing fi
eglass (fi
e-reinforced plastic) shower cubicles for the mining industry. The process involves a number of steps. A chemical called styrene is present in the resin, which is applied with a
ush.
The following YouTube video gives you some idea of the process, if done manually. https:
www.youtube.com/watch?v=BOo8gxp3K3w
(especially the section at 3 minutes onwards)
A group of employees is required to work in a workshop area where the average air concentration of styrene vapour has been measured to be 50 parts per million (ppm), with some variability during the day.
(i) What do the pictograms for styrene signify?
(ii) Outline the short and long term health effects that might arise from styrene exposure
(iii) What is the relevant Australian exposure standard for styrene? Is there a problem in this workplace?
Hints:
Exposure standards：
Some source I will send you.
Health effects
https:
www.atsdr.cdc.gov/PHS/PHS.asp?id=419&tid=74
© D. Pisaniello XXXXXXXXXXAdelaide University XXXXXXXXXXpage 1
An Introduction to Occupational Noise
Part 3: Noise Control
D. Pisaniello
INTRODUCTION
The Australian Standard on Occupational Noise Management (AS/NZS 1269)
constitutes the basis of much of the material presented in this lecture. You are
encouraged to
owse the Standard, which comprises 5 parts:
XXXXXXXXXXPart 0: Overview.
XXXXXXXXXXPart 1: Measurement and assessment of noise immission and exposure.
XXXXXXXXXXPart 2: Noise control management.
XXXXXXXXXXPart 3: Hearing protection program.
XXXXXXXXXXPart 4: Auditory assessment.
Parts 2 and 3 are the most relevant here, although part 4 may be considered
complementary. Strictly speaking, auditory assessment is not a form of noise control,
ut it is a related area of noise management, mainly for health promotion and
compensation purposes. Auditory assessment as a noise control performance indicator
is a flawed concept.
The management aspects of noise control are well covered in the Standard.
However, there are a number of useful resources relating to the technical aspects of
engineering noise control, including active noise control.
In addition, various video products are helpful in this area, as well as in the area of
personal hearing protection.
As the topic of noise control is so large, it will be divided into three sections:
(i) management issues and administrative controls
(ii) engineering noise control
(iii) personal hearing protection
DEFINITIONS
Administrative noise control —a control measure (not including the use of a personal
hearing protector) that reduces the noise to which a person is exposed by means of work
a
angements, including—
(a) the scheduling of work;
(b) job rotation;
(c) limiting the entry of people to areas with excessive noise; and
(d) the observance of quiet work practices.
Engineering noise control —a control measure (not including the use of a personal hearing
protector) that reduces the noise to which a person is exposed by the design or modification of
equipment or the physical working environment, including—
© D. Pisaniello XXXXXXXXXXAdelaide University XXXXXXXXXXpage 2
(a) eliminating noisy equipment;
(b) replacing noisy equipment by quieter equipment;
(c) reducing noise emission;
(d) isolating or enclosing noisy equipment; or
(e) the acoustical treatment of the workplace.
Personal hearing protection —
Interestingly, AS1269 doesn’t give a definition of personal hearing protection, but it
presumably refers to the use of devices that are attached to the heads of individual workers to
educe the transmission of external sounds to the ear drum or skull.
PASSIVE NOISE CONTROL refers to attenuation of noise signals by absorption into
materials (e.g. noise insulation foam), or the reduction of noise transmission by ba
iers etc.
For example, a normal ear plug reduces the transmission of sound along the ear canal.
Acoustic ceiling tiles and carpets abso
some of the sound produced in a room and reduce
eve
eration (i.e. reflected sound).
ACTIVE NOISE CONTROL
means the creation of a destructive
interference between acoustic waves
(see Figure). It requires a
microphone to sense the original
sound, a speaker to pump out “equal
and opposite” sound, a second
microphone to tell whether the
cancellation has been effective, and
an electronic feedback circuit to
continuously control the output of the
speaker, minimizing overall noise.
Active control is effective mainly in the
medium-low frequency range, that is in
the range where the normal noise-
eduction actions lose their effectiveness.
Practical noise reductions in this
frequency range can reach 20 to 30 dB for
periodic phenomena, and 10 to 15 dB for
andom ones, depending on the
application.
FIGURE: LIMIT OF APPLICATION
Possible industrial applications of active control are as follows:
Significant noise reduction can be obtained in closed or restricted spaces (zonal silencing),
mainly in connection with repetitive phenomena. Also the noise emitted at inlets from
exhausts and ducts, e.g. in ventilation systems, can be successfully reduced.
NOISE CONTROL MANANGEMENT ISSUES
Here is an extract from the South Australian WHS Regulations relating to noise:
© D. Pisaniello XXXXXXXXXXAdelaide University XXXXXXXXXXpage 3
57—Managing risk of hearing loss from noise
(1) A person conducting a business or undertaking at a