Effect of room air change rate and room
configuration on airborne and surface
concentration of pesticides released from
vaporisers devices
C J Saunders, P Johnson, J Wheeler,
M Coldwell
Health and Safety Laboratory
[email protected]
ISO 9001:2000
www.hsl.gov.uk
an agency of the Health & Safety Executive
Outline of presentation
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Background
Reasons for the study
Objective
Type of pesticide vaporiser devices
Measurements of ventilation rates in
hotel rooms
• Measurements of pesticide concentration
in a test room
• Emission rates and air concentration
prediction
• Conclusions
Background
• Malaria is present in over
100 countries
• Affects 100 million people
worldwide
• Resulting in approximately
2 million deaths each and
every year
• Consequently a lot of
effort has been put into
effective methods of killing
the mosquito
Why carry out the study?
• In the UK use of non-agricultural and amateur
pesticide products comes under the remit of
HSE Biocides Unit
• Approval by HSE leads to a ‘product license’
• To approve a license HSE needs to consider
efficacy, toxicological, environment and human
exposure
• For the plug in devices HSE had no exposure
data
• Data available based on models - no
experimental data in published literature
Main objective
• Investigate the effect of various
parameters on the airborne and
deposition concentrations of pesticide
typically generated from mosquito
devices
• Not the intention to look at the risk from
pesticides
Pesticides for indoor use
• Two types of electric plug in devices
– Impregnated mat
– Liquid system
• Both use pyrethroid insecticide
– Relatively low toxicity, when compared to
other pesticides
Types of pesticide devices
• Impregnated mat
(Bioallerathrin 40 mg
on each mat)
• Mat slots under grill
• 6 W heater
• Measured interface
temp ~ 130oC
• Lasts 8 –10 hours
Types of pesticide devices
• Liquid (Prallerthrin,
0.87 % pesticide in a
liquid suspension)
• Liquid is wicked by
capillary action
• 7 W heater
• Measured interface
temperature ~ 170oC
• Lasts up to 45 nights
• But use for only 12 hours
per day
Ventilation rates in Hotels rooms
• Two international
hotel chains
approached
• One hotel from each
chain selected
• 3 rooms selected in
each hotel
• Measured air change
rates using tracer gas
technique
Ventilation rates in Hotels rooms
Hotel
A
B
Test
room
Room dimensions
LxWxH (m)
Approximate
room volume
(m3)
Measured air
change rate
6.3 x 3.3 x 2.3
48
1.3
5.6 x 3.5 x 2.3
45
2.2
6.3 x 3.3 x 2.3
48
0.8
7.1 x 3.5 x 2.5
61
1.0
7.0 x 3.8 x 2.5
67
0.4
Complex
geometry
55
4 x 4 x 2.7
43.2
1.3
4.4*
0.05, 0.5, 3
* Window open
View of actual room
Device
Different furniture configurations
Table
Bed
Chair
Supply
Supply
Extract
Chair
Extract
Bed
Room configuration 2
Device
Table
Device
Table
Room configuration 1
Room configuration 3
Chair
Bed
Supply
Device
Extract
Test programme
Test
1
Room
configuration
1
Air change
rate
0.05
2
2
0.05
3
3
0.05
4
1
0.5
5
2
0.5
6
3
0.5
7
1
3
8
2
3
9
3
3
Study design
Device
Effect of air change rate on
deposition (Liquid)
Prallethrin Surface Deposition
air change 0.05
air change 0.5
air change 3.0
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
Position
Average
Floor 4.1
Floor 3.1
Floor 2.1
Floor 1.1
Average
Table 3.1
Table 2.1
Table 1.1
Average
Bed 3.1
Bed 2.1
0.0
Bed 1.1
Ave Concentraion ng cm-2
4.5
Air concentration for different room
configuration (Liquid)
Prallethrin
Concentration ( µ g m-3)
8.0
6.0
1
2
4.0
3
2.0
0.0
Bed
Table
Static (seated) Static (Head)
Position
Air concentration at different
BZ heights (Liquid)
Prallerthrin
Concentration ( µ g m-3)
14
12
10
0.05 ach
8
0.5 ach
6
3 ach
4
2
0
0.84 (Bed)
1.15 (Seated)
Height (metres)
1.6 (Standing)
Prediction of airborne
concentration
• Airborne concentration independent
of room position
• This means that the pesticide over
the period of the test is uniformly
distributed
• To predict airborne concentration we
need emission rate measurements
Emission rate for the liquid device
Prallerthrin
Weight loss of pesticide (mg)
8
7
6
5
4
3
2
Emission rate 0.85 mg h-1
1
0
0
2
4
Time (hours)
6
8
Predicted concentrations for
liquid device
Prallerthrin
0.05 ach
0.5 ach
3 ach
-3
Concentration (µg m )
150
100
50
Emission rate 0.85 mg h-1
0
0
1
2
3
4
Time (hours)
5
6
7
8
Applying a correction factor
ach
Mean
Predicted
airborne conc. airborne conc.
(µg.m-3)
(µg.m-3)
35 ng.cm-2
74
157
0.5
4.1
29.7
Correction factor of 0.138
ach
Mean
Cor. Predicted
airborne
airborne conc.
conc.(µg.m-3)
(µg.m-3)
0.05
11
9.6
0.5
4.1
4.1
1
0.9
3
85
9.6
Device
Main conclusions
• Air change rate significantly affects the
concentration of pesticides, both in the air and
on surfaces
• No significant difference in airborne
concentration of pesticide with height - both
devices
• Surface conc. on the bed and table similar and
higher that floor – both devices
• Possible to use emission rate (with a
correction factor) to predict pesticide air
concentration for other air change rates – but
not room sizes
Thank you for listening