Occupational Exposure to Polycyclic Aromatic ... - ACS Publications

May 12, 2017 - ... to prescribed fires and were highest for firefighters during job tasks that involve ... Related Content ... Environmental Science &...
0 downloads 4 Views 936KB Size
Subscriber access provided by CORNELL UNIVERSITY LIBRARY

Article

Occupational Exposure to Polycyclic Aromatic Hydrocarbon of Wildland Firefighters at Prescribed and Wildland Fires Kathleen Navarro, Ricardo Cisneros, Elizabeth Noth, John R. Balmes, and S. Katharine Hammond Environ. Sci. Technol., Just Accepted Manuscript • Publication Date (Web): 12 May 2017 Downloaded from http://pubs.acs.org on May 13, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 25

Environmental Science & Technology

1

Occupational Exposure to Polycyclic Aromatic

2

Hydrocarbon of Wildland Firefighters at Prescribed

3

and Wildland Fires

4

5

Kathleen M. Navarro1,*, Ricardo Cisneros2, Elizabeth M. Noth1, John R. Balmes1, S. Katharine

6

Hammond1

7 8

1. Division of Environmental Health Sciences, School of Public Health, University of California,

9

Berkeley, Berkeley, CA

10

2. School of Social Sciences, Humanities and Arts, University of California, Merced, Merced,

11

CA

12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

Corresponding Author: Kathleen Navarro School of Social Sciences, Humanities & Arts 5200 N. Lake Road SSM 361A Merced, CA 95343 E-mail: [email protected] Phone: 408-644-0186

TOC Abstract Art

1

ACS Paragon Plus Environment

Environmental Science & Technology

28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64

Abstract

2

ACS Paragon Plus Environment

Page 2 of 25

Page 3 of 25

Environmental Science & Technology

65

Wildland firefighters suppressing wildland fires or conducting prescribed fires work long shifts

66

during which they are exposed to high levels of wood smoke with no respiratory protection.

67

Polycyclic aromatic hydrocarbons (PAHs) are hazardous air pollutants formed during incomplete

68

combustion. Exposure to PAHs was measured for 21 wildland firefighters suppressing two

69

wildland fires and 4 wildland firefighters conducting prescribed burns in California. Personal air

70

samples were actively collected using XAD4-coated quartz fiber filters and XAD2 sorbent tubes.

71

Samples were analyzed for 17 individual PAHs through extraction with dichloromethane and gas

72

chromatograph-mass spectrometer analysis. Naphthalene, retene, and phenanthrene were

73

consistently the highest measured PAHs. PAH concentrations were higher at wildland fires

74

compared to prescribed fires and were highest for firefighters during job tasks that involve the

75

most direct contact with smoke near an actively burning wildland fire. Although concentrations

76

did not exceed current occupational exposure limits, wildland firefighters are exposed to PAHs

77

not only on the fire line at wildland fires, but also while working prescribed burns and while off-

78

duty. Characterization of occupational exposures from wildland firefighting is important to

79

understand better any potential long-term health effects.

80 81 82 83 84 85 86 87 88 89 90 91 92 93 94

Introduction

3

ACS Paragon Plus Environment

Environmental Science & Technology

95

Over the past 10 years approximately 63 million hectares in the United States have been burned

96

by wildland fires. In 2015 27,000 wildland firefighters employed by the federal government

97

worked to suppress wildland fires over 4 million hectares, the highest amount of forested land

98

burned in the last decade.1,2 Prescribed fires are intentionally ignited, low-intensity fires used for

99

land management and ecological benefit and can reduce risks of future wildland fires.3 Annually

100

in the United States, roughly 900,000 hectares are treated with prescribed fire.1 Wildland

101

firefighters suppressing wildland fires or conducting prescribed burns often work long hours, are

102

exposed to high levels of wood smoke. 4,5

103 104

Wildland fires emit large amounts of air pollutants known to cause adverse health effects.

105

Previous studies of wildland firefighters have shown that wood smoke exposure is associated

106

with increases in airway responsiveness, decreases in lung function, and a significant cross-shift

107

difference in circulating cytokine levels.5,6 Gaughan et al. reported that some wildland

108

firefighters had acute lung function decline after exposure to fine smoke particles.7 Past exposure

109

assessments of wildland fires have measured levels of fine and respirable particulate matter

110

(PM2.5, PM4), acrolein, benzene, carbon dioxide, carbon monoxide, formaldehyde, crystalline

111

silica, total particulates, and polycyclic aromatic hydrocarbons (PAHs).4,8 Currently in the United

112

States, wildland firefighters do not wear respiratory protection, as is not currently practical given

113

the physically demanding nature of wildland firefighting.4,5 De Vos et al. 2009, evaluated the

114

use of the negative pressure half face air purifying respirators with organic vapor and

115

formaldehyde filters and reported that they were effective in reducing exposures and provided

116

protection for firefighter’s airway. However, these firefighters only wore respiratory protection

4

ACS Paragon Plus Environment

Page 4 of 25

Page 5 of 25

Environmental Science & Technology

117

for 2 hours, not representative of a full shift (12-16 hours), did not perform any firefighting tasks,

118

and were not protected against carbon monoxide exposure.9

119 120

PAHs are a class of compounds consisting of two or more fused benzene rings.10 They are

121

hazardous air pollutants formed during incomplete combustion and are known mutagens and

122

carcinogens. The International Agency for Research on Cancer has listed benzo[a]pyrene as a

123

human carcinogen, benz[a]anthracene and dibenzo[a,h]anthracene as probable human

124

carcinogens and benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, chrysene,

125

and naphthalene as possible human carcinogens.11–13 Exposure to PAHs has also been associated

126

with cardiopulmonary mortality and decreased immune function.14,15 Past occupational health

127

studies found that exposure to PAHs was associated with a higher risk of lung and bladder cancer

128

and skin cancer from dermal exposure to PAHs.16,17

129 130

Lower molecular weight PAHs exist in the environment in the gas phase or partitioned between

131

the gas and particle phases, while higher molecular weight PAHs exist in the particle phase.8 Past

132

studies have demonstrated that open-air burning of wood generates more gas-phase than particle-

133

phase PAHs.18–20 Only a few studies have characterized personal exposures to PAHs during

134

wildland fires. Materna et al. measured PAH concentrations in northern California during three

135

wildfire seasons (1986-1989) and reported highest mean concentrations for pyrene, phenanthrene

136

and fluoranthene. A National Institute for Occupational Safety and Health (NIOSH) Health

137

Hazard Evaluation Report completed in 1994, detected acenaphthene, anthracene, and

138

naphthalene in the gaseous phase and acenaphthene, anthracene, benzo[b]fluoranthene, and

139

fluoranthene in the particulate phase in the breathing zone of wildland firefighters in Yosemite

5

ACS Paragon Plus Environment

Environmental Science & Technology

140

National Park.21 During prescribed burning of wood piles, Robinson et al. detected only gas-

141

phase naphthalene, phenanthrene, and fluorene in personal air samples.22

142 143

The objective of our study was to characterize exposures to PAHs of wildland firefighters

144

suppressing wildland fires and conducting prescribed fires.

145 146

Methods

147

Study Participants and Location. The study population consisted of members of an

148

Interagency Hotshot Crew (IHC), a Wildland Fire Engine Crew, and participants of a prescribed

149

fire training event. Prescribed fire samples were collected in October 2014 and 2015 at two

150

annual trainings hosted by the Mid-Klamath Watershed Council and The Nature Conservancy in

151

the Klamath River region of northern California. All prescribed burns conducted were broadcast

152

burns, where fire was applied directly to a predetermined area and is confined to that space.

153

Wildland fire samples were collected at two fires, during day shifts of the Willow Fire from July

154

26, 2015 - August 1, 2015 and during night shifts at the Rough Fire from September 1 - 5, 2015.

155

The Willow Fire burned 2,307 ha (5,702 ac) in the Sierra National Forest.23 The Rough Fire

156

burned over 61,000 ha (151,623 ac) in Kings Canyon National Park, Sequoia National Forest,

157

Sierra National Forest, and adjoining state and private lands.24

158 159

Wildland firefighters perform a variety of job tasks to suppress fires; these include operating a

160

fire engine, fire line construction, holding, patrol, staging, mop-up, and firing operations. Engine

161

operators work as a part of an engine crew and operate the diesel pumps that provide water to

162

crews working near the fire. Fire line construction involves clearing vegetation and digging or

6

ACS Paragon Plus Environment

Page 6 of 25

Page 7 of 25

Environmental Science & Technology

163

scrapping down to mineral soil with hand tools to create a break in fuels to stop the spread of a

164

fire. Crew members engaged in holding walk along the active fire and check that it has not

165

crossed the fire line; if it has, suppression tactics are used to control the fire, while patrol

166

involves inspecting an inactive fire perimeter. Often crews will wait at a location near the fire to

167

hear where they have been assigned (staging). After the fire has been controlled, crews will

168

extinguish any burning material by digging out the burning material or applying water to stop

169

any smoldering material that may re-ignite a fire (mop-up). Ignition of fuels with torches filled

170

with a 3:2 diesel/unleaded gasoline mixture is used at prescribed fires, and often in wildland fire

171

suppression (firing). Additionally, when working on a large wildland fire, firefighters will sleep

172

and eat at a base camp that provides logistical support (incident command base) and is situated

173

close to the fire. Firefighters working at the Willow Fire performed the following job tasks:

174

engine operator, fire line construction, holding, mop-up and firing. At the Rough Fire,

175

firefighters performed the following job tasks: engine operator, holding, patrol, and staging.

176 177

The study protocol was approved by the UC Berkeley Committee for Protection of Human

178

Subjects and informed consent was obtained from each study participant.

179 180

Exposure Assessment. Gas-phase and particle-bound PAH samples were collected using a

181

XAD2 sorbent tube and a 37mm closed face cassette (SKC, Inc. Eighty Four, PA) with two

182

quartz fiber filters (PallFlex Tissuquartz) in series impregnated with XAD4, respectively.25–27 Air

183

was drawn through the cassettes using SKC Airchek 52 sampling pumps (SKC, Inc. Eighty Four,

184

PA) at 1.5 – 2 L/min and the XAD2 sorbent tubes using PAS-500 Micro Air Samplers (Spectrex,

185

Redwood City, Ca) sampled at 0.2 L/min. To verify flow rates, pumps were calibrated before

7

ACS Paragon Plus Environment

Environmental Science & Technology

186

and after each sampling event with representative sampling media using a Defender 510 DryCal

187

(Mesa Labs, Inc. Butler, NJ).

188 189

Sampling pumps were placed inside the pack and cassettes and XAD2 sorbent tubes were placed

190

as close to the breathing zone as possible, on the shoulder straps of each firefighter’s gear pack,

191

to prevent interference with work tasks. These packs contain emergency fire shelters, food, and

192

water and are required to be worn while firefighters are working on an active fire. Depending on

193

work schedule and location, pumps were started when crews left the incident command base

194

(ICB) or when they arrived to their work location for the day on the wildland or prescribed fire.

195 196

At the end of each shift, participants self-reported the job duty they performed during the

197

majority of their work shift and rated the smoke conditions they experienced (none, mild,

198

moderate, severe).7 Participants were also asked if they used a chainsaw during the work shift,

199

which could potentially add to their PAH exposure.

200 201

Laboratory Analysis and Quality Control. Prior to coating with XAD4, filters were baked at

202

800 °C for three hours to remove contaminants. Coated filters were stored in baked amber jars

203

until sampling. Filters were extracted by sonication in dichloromethane followed by filtration

204

under vacuum. XAD2 sorbent tubes were extracted by shaking in dichloromethane (2 mL) for

205

one hour. All analyses were performed on a gas chromatograph (Hewlett Packard model 6890)

206

equipped with a 30 m (50%-Phenyl) methylpolysiloxane-fused silica capillary column and a

207

5972 Mass Selective Detector operated in selected ion-monitoring mode. XAD2 sorbent tubes

208

were analyzed for naphthalene (NAP). Filters were analyzed for 17 PAHs: acenaphthylene

8

ACS Paragon Plus Environment

Page 8 of 25

Page 9 of 25

Environmental Science & Technology

209

(ACY), acenaphthene (ACE), fluorene (FLU), phenanthrene (PHE), anthracene (ANT),

210

fluoranthene (FLT), pyrene (PYR), and retene (RET), benz[a]anthracene (BAA), chrysene

211

(CHR), benzo[b]fluoranthene (BBF), benzo[k]fluoranthene (BKF), benzo[a]pyrene (BAP),

212

indeno[1,2,3-cd]pyrene (ICP), dibenz[a,h]anthracene (DBA), and benzo[ghi]perylene (BGP).

213

Sorbent tubes and filters were tested for adequate recoveries with spiked samples for the full

214

extraction and analysis procedure. The spiked recovery of naphthalene on sorbent tube was

215

114%. The mean spiked recovery for the 17 PAH measured by filter was 96%, with individual

216

PAH recoveries ranging from 78% to 127%. PAH concentrations of individual PAHs measured

217

by sorbent tubes and filters were summed for statistical analysis. However, some personal

218

samples consisted of only a filter sample and were not paired with a sorbent tube, so NAP

219

concentrations were not measured.

220 221

During the first analyses of a set of samples, selected XAD sorbent tubes and filters were

222

checked for breakthrough. If there was evidence of breakthrough, the front and back sections of

223

all filters or tubes from that sampling event were analyzed separately and the amount of

224

breakthrough was quantified. We determined breakthrough by whether the amount of each

225

analyte in the back filter or tube was greater than 25% of the total amount of analyte detected in

226

both the front and back filters or sections of sorbent tubes. Field blanks for filter cassettes (n=2-

227

4) and XAD sorbent tubes (n=2-4) were collected at each sampling event to examine

228

contamination of sampling media in the field or during transport. All samples were adjusted for

229

blank concentrations by media type and event. Blank correction for the 16 PAHs on the filters

230

was generally low with all blank mass less than 16 ng, except for fluorene at the Rough Fire. The

231

blank correction for fluorene on filters at the Rough Fire was high – 37 ng – but the

9

ACS Paragon Plus Environment

Environmental Science & Technology

232

concentrations at the Rough Fire were, on average, a magnitude higher. The blank correction

233

for naphthalene collected by sorbent tubes was 7 to 18 ng. The LQ was determined for each PAH

234

and day of laboratory analysis. The average LQ was 2.6 ng (typically 3.7 ng m-3) with a range of

235

1.0 – 5.3 ng (1.71 – 7.14 ng m3). To perform statistical analyses, samples that were less than the

236

LQ were assigned the LQ divided by 2.

237 238

Statistical Methods. Characteristics of participants and samples collected from participants are

239

presented in Table 1. PAHs were summed to create summary measures by the number of fused

240

benzene rings. We created summary metrics for low molecular weight PAHs (Σ3 ring PAH),

241

medium molecular weight PAHs (Σ4 ring PAH), high molecular weight PAHs (Σ5-6 ring PAH),

242

and a total PAH metric of 3 through six ring PAHs, composed of 15 PAHs (Σ15 PAH). These

243

summary measures did not include naphthalene or retene. The geometric mean (GM) and

244

geometric standard distribution (GSD) were calculated for each PAH analyte and summary PAH

245

metrics. We used SAS 9.4 (SAS Institute Inc. Cary, NC) and R v. 3.1.0 (R Foundation, Vienna,

246

Austria) for all data cleaning, calculations, and graphical processing.

247 248

Results

249 250

Twenty-five wildland firefighters participated in personal air sampling; 15 were members of an

251

IHC, 6 were members of an engine crew and 4 were members of a prescribed burn crew (Table

252

1). Participants working at wildland fires were primarily males (85%) and worked the day shift

253

(71%), while approximately half of the participants working at prescribed fires were male. Only

254

three participants (10%) at wildland fires used a chainsaw while working. All participants were

10

ACS Paragon Plus Environment

Page 10 of 25

Page 11 of 25

Environmental Science & Technology

255

non-smokers. When asked to rate their smoke exposure, participants at wildland fire and

256

prescribed fires mostly rated their smoke exposure during their work shift as mild and moderate.

257

A small subset of wildland fire participants (14%) rated their smoke exposure as severe.

258 259

The summary metrics of the PAH concentrations are reported in Table 2. Arithmetic mean and

260

standard deviation for each sampling event can be found in the Supplemental Information (Table

261

S.2). Table S.1 presents the sampling time and number of samples collected for each of personal

262

exposure sampling events. Distribution of each PAH analyte and Σ15 PAH exposures by job

263

tasks performed at prescribed fire and wildland fires are presented in Figures 1 and 2,

264

respectively

265 266

Prescribed Fire. Participants at prescribed fires reported performing firing, holding, and mop-up

267

tasks (N=3 for each task) and also twice performing a combination firing and holding tasks.

268

Personal job task samples had mean sampling times that ranged from 340 to 439 minutes (Table

269

S.2).

270 271

The PAH analyses of samples collected at prescribed fires revealed that lower molecular weight

272

PAHs were detected more frequently and at higher concentrations compared to higher molecular

273

weight PAHs. With the exception of anthracene, all 2 and 3-ring PAHs were detected in at least

274

73% of all the samples. Detection of 4, 5, and 6-ring PAHs ranged from 33% to 73% of all

275

samples collected. The GM for Σ3 ring PAH was 135 ng m-3 and contributed the most to the Σ15

276

PAH GM of 265 ng m-3 compared to the GM for Σ4 ring PAH (54 ng m-3) and Σ5-6 ring PAH

277

(25 ng m-3). The GMs of the highest concentration of PAHs measured were 669 ng m-3, 76 ng m-

11

ACS Paragon Plus Environment

Environmental Science & Technology

278

3

, and 50 ng m-3 for NAP, RET, and PHE, respectively. NAP concentrations ranged from less

279

than 4 ng m-3 to 5073 ng m-3 and NAP was consistently was the highest measured PAH. NAP

280

GM concentration was 2.5 times higher than the Σ15 PAH GM.

281 282

PAH exposures measured at prescribed fires were found to vary by job task (Figure 1).

283

Firefighters performing firing and holding during the same shift at prescribed fires were

284

consistently exposed to significantly higher levels of PAHs compared to those doing a single task

285

-- firing, holding, or mop-up. Firing had higher concentrations of ACY, ACE, and FLT

286

compared to holding or mop-up. Firefighters performing mop-up had higher distributions of

287

PHE, FLU, and RET concentrations. Across all job categories, naphthalene was the highest

288

measured PAH with a median ranging from 304 ng m-3 for holding to 2918 ng m-3 for

289

firing/holding. When comparing Σ15 PAH across job task, firing/holding had the highest

290

median, followed by firing, holding, and mop-up.

291 292

Wildland Fire. A total of 28 XAD4-coated filters and 21 XAD-2 sorbent tubes were collected as

293

personal samples at wildland fires. Participants sampled at wildland fires mostly constructed fire

294

line (8) and performed mop-up (8) and holding (5). Personal job task samples had mean

295

sampling times that ranged from 186 to 778 minutes (Table S.1). PAHs with 2, 3 or 4 fused

296

benzene rings were consistently detected above the LQ, with the percent detected ranging from

297

75% to 100%. PAHs with 5 or 6 fused benzene rings were detected in only 29% to 75% of

298

samples collected. Breakthrough on filters was detected for ACY, ACE, FLU, PHE, ANT, FLT,

299

(all 3-ring PAHs) and PYR (a 4-ring PAH), which indicates that those samples could have been

300

an underestimate of the true concentration.

12

ACS Paragon Plus Environment

Page 12 of 25

Page 13 of 25

Environmental Science & Technology

301 302

During wildland firefighting, Σ15 PAH mean concentration was 586 ng m-3 and ranged from 88

303

ng m-3 to 7925 ng m-3. When comparing GM concentration by molecular weight, NAP was

304

highest 3189 ng m-3 followed by Σ3 ring PAHs (429 ng m-3), Σ4 ring PAH (90 ng m-3) and Σ5-6

305

ring PAH (38 ng m-3) molecular weight PAHs. NAP and RET had the highest GM concentration

306

of all PAHs detected, 3189 ng m-3 and 3,641 ng m-3, respectively. RET was the highest single

307

measured PAH (24,562 ng m-3). PHE was also detected at elevated concentrations (GM = 210 ng

308

m-3) followed by FLU (GM = 77 ng m-3) and ACY (GM = 72 ng m-3).

309 310

Firefighters were exposed to different concentrations of PAHs based on their job task (Figure 2).

311

Firefighters performing holding, patrol, and staging tasks often had higher measured

312

concentrations of PAHs compared to firefighters performing fire line construction, firing, and

313

mop-up tasks. NAP was consistently the highest measured PAH across all job tasks, and had a

314

median concentration of 8358 ng m-3 and 3946 ng m-3 for holding and patrol tasks respectively

315

and a measured concentration of 6258 ng m-3 staging. Firefighters performing holding and patrol

316

tasks were exposed to elevated levels of benzo[a]pyrene compared to other job tasks. When

317

compared by job task, holding had the highest median for Σ15 PAH of 322 ng m-3, ranging from

318

182 to 7935 ng m-3 . Not including NAP and RET concentrations, firefighters performing engine

319

operator, holding, mop-up, patrol, and staging duties were predominantly exposed to PHE.

320

Firefighters performing firing operations were predominately exposed to FLU when compared to

321

the other 15 PAHs. Across all job tasks, the 3-ring PAHs had higher concentrations compared to

322

the 4-ring and 5-6 ring PAHs.

323

13

ACS Paragon Plus Environment

Environmental Science & Technology

324

Discussion

325 326

Our study objectives were to quantify personal exposures to PAHs of firefighters exposed to

327

smoke at wildland and prescribed fires as well as off-duty at base camps (“staging”). Generally,

328

firefighters working at both wildland and prescribed fires categorized their smoke exposure as

329

mild to moderate. We detected measurable concentrations of 17 PAHs in personal samples on

330

firefighters at prescribed and wildland fires. NAP, RET, and PHE were consistently the highest

331

measured PAHs at all sampling scenarios. Lower molecular weight PAHs (Σ3ring PAH) were

332

2.5 to 11 times higher compared to Σ4 and Σ5-6 ring PAHs and contributed the most mass to the

333

Σ15 PAH metric at wildland and prescribed fires.

334 335

Our measured concentrations of PAHs were consistent with those reported by Materna et al. for

336

12 particle-phase PAHs (4 – 257 ng m-3).18,28 However, the PAH concentrations measured by

337

Reh et al. in Yosemite National Park (range 600 – 35,900 ng m-3) were higher than our measured

338

GMs and were closer to our measured maximum concentrations. Participants in that study were

339

from two Type 1 crews (N=5) and performed firing, holding, and mop-up tasks. Robinson et al.

340

evaluated PAH exposure at prescribed burning of piles, where debris is piled together and

341

burned, and were able to detect only NAP, FLU, and PHE concentrations between