RE-CALIBRATING HEALTH RISK ASSESSMENT IN BUSH FIRE … · 2019. 12. 13. · BUSH FIRE FIGHTING Zach Bentley Occupational Hygiene Advisor Rio Tinto Overview of study Accurate characterisation

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RE-CALIBRATING HEALTH RISK ASSESSMENT

IN

BUSH FIRE FIGHTING

Zach Bentley

Occupational Hygiene Advisor

Rio Tinto

Overview of study

Accurate characterisation of compounds liberated during vegetation burns is essential to ensure that the controls implemented are sufficient to protect worker and community health.

The aim of this study was to investigate if a broader suite of compounds potentially present in the combustion of vegetation material may pose a credible health risk to workers. This work was framed specifically in the context of bush fire fighting however is relevant to broader vegetation burn activities.

The steps taken to date are as follows:1. Review of literature assessing exposure to broader suite of compounds for vegetation fires

around the world2. Identifying commonalities in detections for compounds in the review of this limited literature.3. Design a sample plan based on these commonalities4. Characterise vegetation in burn area5. Complete exposure assessment during burn6. Result interpretation and reporting

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Introduction

The hypothesis of this study is that that analytes including Volatile Organic Compounds (VOC), Hydrogen Cyanide (HCN) and Aldehydes could be present in the by-products of bushfire smoke and that the prevalence of these compounds may be affected by parameters including:

– Type of vegetation

– Age of vegetation

– The intensity at which the vegetation is burnt

– Prevailing weather conditions at the time of combustion

– Phase of fire/ burn

– Worker and or community interface with the products of combustion during vegetation burns

Review of literature – Study 1

Respiratory Irritants in Australian Bushfire Smoke: Air Toxics Sampling in a Smoke Chamber and During Prescribed Burns (De Vos et al., 2008)

Fuel Source: Australian Native Banksia and Coastal Heath.

Location: Australia, WA

Contaminants observed: CO, Benzene, Formaldehyde, Acetaldehyde, Acrolein, Toluene, Xylenes and Phenol.

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Review of literature – Study 2

BTEX EMISSIONS DURING PRESCRIBED BURNING IN FUNCTION OF COMBUSTION STAGE AND DISTANCE FROM FLAME FRONT (Barboni and Chiaramonti, 2010)

• Fuel Source: Forrest fire (non-specific) also considers accelerant used in drip torches.

• Location: France.

• Contaminants observed: VOC including: Benzene, Toluene, Ethylbenzene and Xylene (BTEX).

The most significant finding in the study was the results for Benzene emissions during the smouldering phase of the fire at a distance of between 1-10 meters from the fire front. Benzene concentrations for these workers ranged between 0.093-18mg/m3, this exceeded the local short term exposure limit (STEL) used in France of 16mg/m3.

Review of literature – Study 3

Australian firefighters' exposure to air toxins during bushfire burns of autumn 2005 and 2006

• Fuel Source: Eucalypt, Grassland, Mallee Heath.

• Location: Australia – Various states.

• Contaminants observed: Formaldehyde (significant), CO (significant), VOC.

Relevant findings of the study:

•Benzene and Toluene were detected in 100% of samples taken

•40 firefighters across various states in Australia

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Methodology – Suite and Equipment

The review of literature informed a suite of analytes for assessment as follows:

– Volatile Organic Compounds (VOC)

– Hydrogen Cyanide (HCN)

– Aldehyde and Ketones

Monitoring was completed via a combination of real time and passive sampling.

Real time equipment:

• UltraRae 3000 PGM-7360 with a 9.8eV lamp

• MultiRAE Lite PGM-6208 with a HCN sensor

Passive badges used:

• SKC 575-002: VOC Monitoring

• SKC 590-400: Hydrogen Cyanide Monitoring

• SKC 500-100: Aldehyde and Ketone Monitoring

Methodology – Controlled burn

Approximately 8m3 of vegetation was burnt in controlled setting in the southwest of Western Australia. The vegetation was sourced locally and included:

• Western Australian Peppermint Trees (Agonis flexuosa)

• Tuart Tree (Eucalyptus gomphocephala)

• Apple of Sodum (Solanum linnaeanum)

Exposure monitoring was completed for a duration of 5 hours once the burn was self sustaining. Efforts were made to correlate the real time readings for VOC and HCN against the following parameters:

• Type of vegetation

• Age of vegetation

• Intensity of fire

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Fig 1: VOC graph Fig 2: HCN measurements

Summary of results

Summary of real time VOC detections >1.0ppm

Data Point VOC (ppm)

4 1.12

22 7.97

48 6.63

54 6.43

55 1.59

77 8.5

78 6.04

88 19.58

89 2.3

107 1

119 6.21

121 2.5

122 7.23

161 1.6

162 4.24

174 2.82

175 1.52

176 2

185 1.88

Summary of real time detections of HCN >1.0ppm

Data Point HCN (ppm)

54 1

87 5

88 1.5

89 4

90 1

94 1

118 1.5

120 2

121 3.5

122 1

160 1

161 1.5

205 1

Summary of Benzene detectionsData point Benzene (ppm)

1 0.12

2 0.13

3 0.12

4 0.12

5 0.12

Summary of results – by detection

Relevant exposure standards (TWA): Safe Work Australia

Benzene 1.0 ppm

HCN 10 ppm (peak limitation)

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Summary of results

• Five (5) grab samples collected for Benzene all produced detections with results ≥0.12ppm.

• Real time VOC and HCN readings varied throughout the burn and were most significant when fresh vegetation was added to the fully developed fire.

• VOC measurements ranged from being below the limit of detection to >19.0ppm.

• HCN results ranged from being below the limit of detection to 5.0ppm.

• Although passive sampling badges were deployed for the duration of the burn, these badges were voided due to water ingress.

Limitations • Inclement weather on the day of monitoring resulted in all passive badges having

significant rainwater ingress. It was advised by the laboratory that this may have compromised the analysis of these badges. It was noted that there was significant disparity between the real time monitoring and the passive sampling completed on this study.

• The presence of the above mentioned rain also significantly limited the intensity of the burn.

• The type and age of vegetation was limited to the three predominate varieties available on the property.

• A small amount of diesel (200mL) and newspaper was used in the ignition phase of the fire with a view to develop the burn to a point where it would be self-sustaining. In an effort to avoid false detections, no analysis was completed until this material had combusted and the fire was self-sustaining.

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Conclusion

• The presence of HCN and VOCs including Benzene were observed during this study.

• Notable measurements produced readings for Benzene and HCN equivalent to 13% and 50% of the permissible exposure standard respectively

• These limited findings underscore the need for further investigation to assess the credibility of these compounds in a health context

• Further investigation into potential correlations between vegetation type, age and their subsequent risk to worker and/or community health would be beneficial.

*Caution should be exercised when comparing real time results to permissible exposure standards.

References • Cook, A. (2018). [online] Bushfirecrc.com. Available at:

http://www.bushfirecrc.com/sites/default/files/managed/resource/health_risks_of_airtoxics_in_bu shfire_smoke_-_ac.pdf [Accessed 10 Oct. 2018].

• Barboni, T. and Chiaramonti, N. (2010). BTEX Emissions During Prescribed Burning in Function of Combustion Stage and Distance From Flame Front. Combustion Science and Technology, 182(9), pp.1193-1200.

• Miranda, A., Martins, V., Cascão, P., Amorim, J., Valente, J., & Tavares, R. et al. (2010). Monitoring of firefighters exposure to smoke during fire experiments in Portugal. Environment International, 36(7), 736-745. doi: 10.1016/j.envint.2010.05.009

• De Vos, A., Reisen, F., Cook, A., Devine, B. and Weinstein, P. (2008). Respiratory Irritants in Australian Bushfire Smoke: Air Toxics Sampling in a Smoke Chamber and During Prescribed Burns. Archives of Environmental Contamination and Toxicology, 56(3), pp.380-388.

• (2019). Retrieved 14 October 2019, from https://www.safeworkaustralia.gov.au/system/files/documents/1804/workplace-exposure-standards-airborne-contaminants-2018_0.pdf