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Effectiveness of individual- and household-level protective actions in reducing symptoms associated with hydrogen sulfide chronic low-level exposure

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Effectiveness of individual- and household-level protective actions in reducing symptoms associated with hydrogen sulfide chronic low-level exposure

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Content EFFECTIVENESS OF INDIVIDUAL- AND HOUSEHOLDLEVEL PROTECTIVE ACTIONS IN REDUCING SYMPTOMS
ASSOCIATED WITH HYDROGEN SULFIDE CHRONIC
LOW-LEVEL EXPOSURE
by
Jennifer Ahumada
A Thesis Presented to the
FACULTY OF THE USC KECK SCHOOL OF MEDICINE
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE
(APPLIED BIOSTATISTICS AND EPIDEMIOLOGY)
August 2024
Copyright 2024 Jennifer Ahumada

ii
Table of Contents
List of Tables .................................................................................................................................iii
Abstract.......................................................................................................................................... iv
Chapter One: Introduction .............................................................................................................. 1
Chapter Two: Methods ................................................................................................................... 6
Study Design and Inclusion Criteria ........................................................................................... 6
Questionnaire .............................................................................................................................. 6
Exposure Modeling ..................................................................................................................... 6
Statistical Analysis...................................................................................................................... 7
Chapter Three: Results.................................................................................................................... 9
Descriptive Statistics................................................................................................................... 9
Association Between Health Symptoms and H2S Exposure..................................................... 10
Impact of Adding Protective Actions to the Health Symptoms and H2S Exposure Models..... 10
Interactions Between H2S Exposure and Protective Actions.................................................... 11
Chapter Four: Discussion.............................................................................................................. 14
Summary of Findings................................................................................................................ 14
Implications of Results.............................................................................................................. 16
Strengths and Limitations.......................................................................................................... 16
Chapter Five: Conclusion ............................................................................................................. 19
References..................................................................................................................................... 20
Appendix A................................................................................................................................... 25

iii
List of Tables
Table 1. Characteristics of Participants ........................................................................................ 25
Table 2. Effect of 0.1 ppb Increase in H2S Concentrations on Health Symptoms Adjusted
for Age, Sex, and Current Smoking Status................................................................................... 26
Table 3. Effect of 0.1 ppb Increase in H2S Concentrations on Health Symptoms Adjusted
for Window Closure, Age, Sex, and Current Smoking Status...................................................... 29
Table 4. Effect of 0.1 ppb Increase in H2S Concentrations on Health Symptoms Adjusted
for Air Purifier Use, Age, Sex, and Current Smoking Status....................................................... 30
Table 5. Effect of 0.1 ppb Increase in H2S Concentrations on Health Symptoms Adjusted
for Outdoor Avoidance, Age, Sex, and Current Smoking Status ................................................. 31
Table 6. Effect of 0.1 ppb Increase in H2S Concentrations on Health Symptoms Adjusted
for Outdoor Exercise Avoidance, Age, Sex, and Current Smoking Status................................... 32
Table 7. Statistical Significance of Interaction Terms Between H2S Concentration and
Each Protective Action ................................................................................................................. 33

iv
Abstract
Oil refineries and wastewater treatment facilities expose residents of Carson, California,
and surrounding communities to chronic low levels of hydrogen sulfide (H2S). We conducted
community-based questionnaires and modeled H2S exposure to assess the health effects of low
H2S concentrations and the effectiveness of personal- and household-level protective actions.
The median estimated H2S concentration of participants during the month of survey completion
was 0.29 parts per billion (ppb) (IQR: 0.15 ppb). After adjusting for age, sex, and smoking
status, every 0.1 ppb increase in H2S exposure is associated with 1.41 times higher odds of
nosebleeds (95% CI:1.03 - 1.93; p = 0.03), 1.50 times higher odds of a runny nose (95% CI: 1.03
- 1.71; p = 0.03), 1.50 times higher odds of a sore throat (95% CI: 1.17 - 1.96; p < 0.01), and
1.34 times higher odds of difficulty concentrating (95% CI: 1.05 - 1.72; p = 0.02). The effect of
H2S concentration on the likelihood of reporting chest tightness (p = 0.01), difficulty breathing (p
< 0.01), loss of balance (p = 0.01), burning eyes (p = 0.01), and increased tearing (p = 0.03)
differed depending on whether participants closed their windows or used air purifiers to protect
themselves from outdoor odors in the previous month. No protective action significantly
decreased the odds of experiencing health symptoms once stratified. The results of this study
suggest that there may be health effects at lower concentrations of H2S than previously studied.
The absence of significant symptom reductions when taking protective actions suggests that
individual- and household-level may not be effective at very low concentrations, emphasizing
the need for more regulatory and community-level solutions.

1
Chapter One: Introduction
Hydrogen sulfide (H2S) is a colorless gas with a strong rotten-egg-like odor. H2S is
emitted naturally from geothermal and volcanic sources and through human activities. Industrial
practices such as oil and gas processing, coal gasification, and pulp and paper manufacturing
release it as a byproduct (Bhomick & Rao, 2014; Habeeb et al., 2017; Malone Rubright et al.,
2017). Elevated levels of H2S can be found in neighborhoods near industrial facilities,
wastewater plants, landfills, and animal feeding operations (Batterman et al., 2023; Bhomick &
Rao, 2014; Malone Rubright et al., 2017). Most people can smell H2S at around 0.5 to 300 parts
per billion (ppb) concentration in the air (ATSDR, 2016). Ambient air concentrations from
natural sources range between 0.11 and 0.33 ppb (ATSDR, 2016). In urban areas, concentrations
of H2S are generally below one ppb, but levels exceeding 90 ppb have been detected in
communities living near natural or industrial sources (ATSDR, 2016).
Acute exposure to H2S concentrations over 20,000 ppb, which may result from being
very proximal to sources or from a larger number of sources or emissions, has been well studied
and is known to have health effects such as fatigue, headaches, and dizziness (ATSDR, 2016).
Acute exposure to concentrations over 500,000 ppb can cause severe health effects, including
death (ATSDR, 2016). Observational community studies on the impact of chronic low-level
exposure to H2S have found that residents living near those industrial sources experience
neurological, respiratory, and ocular symptoms at higher rates. Residents living near H2S
emitting facilities reported neurological symptoms such as headaches, memory loss, fatigue, loss
of balance, and loss of concentration (Kilburn & Warshaw, 1995; Kilburn, 2012; Legator et al.,
2001; Partti-Pellinen et al., 1996). They experienced respiratory symptoms such as cough,
breathlessness, wheezing, and nose and throat irritation (Bates et al., 2013; Finnbjornsdottir et

2
al., 2016; Jaakkola et al., 1990; Kilburn & Warshaw, 1995; Legator et al., 2001; Marttila et al.,
1995; Nuvolone et al., 2019; Partti-Pellinen et al., 1996). Nearby residents have also reported eye
irritation, depression, and hopelessness (Jaakkola et al., 1990; Kilburn, 2012; Legator et al.,
2001; Marttila et al., 1995; Saadat et al., 2006; Villeneuve et al., 2009). However, there have
been similar studies that found mixed results, and many have reported null findings regarding the
effects of chronic low-level exposure to H2S on neurological, respiratory, and ocular symptoms
(Bates et al., 2002; Bates et al., 2013; Inserra et al., 2004; Legator et al., 2001; Nuvolone et al.,
2019; Partti-Pellinen et al., 1996).
Carson, CA, is a diverse urban city in the South Bay of Los Angeles County. Based on
2020 summary statistics from the U.S. Census Bureau, 40.3% of the Carson population identified
as Hispanic/Latino, 25.5% as Asian, 22.5% as Black, and 6.3% as non-Hispanic/Latino White.
Oil refineries, highways, ports, and other industrial facilities overburden Carson and the
surrounding communities. The proximity of residential areas to these industrial activities
potentially exposes residents to elevated levels of H2S, other air pollutants, and various
environmental hazards. In Southern California, communities of color often experience a
disproportionate burden of environmental contaminants (Morello-Frosch et al., 2002). The
California Communities Environmental Health Screening Tool (CalEnviroScreen) designates
disadvantaged communities by assessing pollution burden and population characteristics such as
sensitive populations, education, linguistic isolation, poverty, unemployment, and housing
burden (California OEHHA, 2023). All the communities in the study area ranked in the top 50th
percentile in pollution burden statewide, and many of these communities ranked in the top 90th
percentile (California OEHHA, 2023).

3
On October 3rd, 2021, the South Coast Air Quality Management District (South Coast
AQMD) started receiving odor complaints from residents near Carson (South Coast AQMD,
2022). H2S reached 230 times California's nuisance standard, peaking at 7,000 parts per billion
(South Coast AQMD, 2022). Ambient concentrations fluctuated but remained elevated along the
Dominguez Channel in Carson for over a month (South Coast AQMD, 2022). In early
December, officials determined that runoff from a warehouse fire on September 30th caused the
H2S spike (City News Service, 2021; Chung, 2021; Sahagún, 2022). The ethanol-based products
stored in the warehouse accelerated the anaerobic decay of organic materials in the Dominguez
Channel (City News Service, 2021; Chung, 2021; Sahagún, 2022).
Officials recommended that residents keep their windows closed, use HVAC systems
with HEPA or activated carbon filters, use carbon-activated portable purifiers, relocate if
experiencing persistent symptoms, and seek immediate medical care if symptoms worsened (Los
Angeles County Department of Public Health, 2021). On October 12th, Los Angeles County
started a reimbursement program for purchasing HVAC air filters, portable HEPA air filters, and
temporary relocation (Los Angeles County Department of Public Health, 2021; Los Angeles
County Supervisor's Office, 2024). Throughout the event, the county provided about 40,000 air
purifiers and paid for 3,400 households to stay in hotel rooms (Chung, 2021).
During the four weeks of the event, residents in the Carson area experienced a 24 %
increase in emergency department visits for all respiratory system diseases, a 38% increase for
asthma, a 26% increase for acute upper respiratory infections, a 21% increase for dizziness, and a
25% increase for migraines and headaches (Quist & Johnston, 2023a). A rapid survey revealed
that during the first week of the odor event, 75% of respondents experienced headaches, 72%
experienced dizziness, 66% reported burning eyes, 66% reported fatigue, 65% reported nausea,

4
and 63% had difficulty sleeping (Quist & Johnston, 2023b). About half of the respondents
experienced anxiety, difficulty concentrating, and difficulty breathing (Quist & Johnston,
2023b). 70% reported that their physical health worsened, and 58% reported that their mental
health worsened during the event (Quist & Johnston, 2023b). At the time of the survey, only
13% felt that the odor issue had been completely resolved (Quist & Johnston, 2023b). In late
January 2022, the South Coast AQMD removed a temporary H2S monitor near the channel,
marking the end of the odor event (South Coast AQMD, 2022). About a year after the odor
event, some residents reported feeling fearful and anxious about the possibility of future odor
events (Quist et al., 2024). Since the Carson area has refineries and other industrial facilities
emitting H2S and other malodorous pollutants, residents are still susceptible to odors and their
health effects.
Odors from industrial sources can disrupt the daily activities of nearby residents, leading
them to close windows, limit outdoor activities, and avoid outdoor exercise (Brancher et al.,
2017; Heaney et al., 2011; Ulutaş et al., 2021; Wing et al., 2008). However, there is very limited
literature on what personal- and household-level protective actions people living near industrial
sites can take to protect themselves from H2S and other odors. Most of the literature focuses on
community-level engineering solutions for odor mitigation (Chen et al., 2012; Hernandez et al.,
2012; Lewkowska et al., 2016; Tomar & Abdullah, 2003; Wani et al., 1999).
By evaluating which personal- and household-level protective actions reduce symptoms
associated with H2S exposure, agencies can develop more effective guidelines to mitigate
elevated levels of H2S. The study aims to contribute to the existing literature on chronic lowlevel exposure in communities living near industrial sites and determine whether engaging in
protective actions against H2S exposure is associated with reduced odds of experiencing health

5
symptoms. Since most of the literature focuses on rural communities, adding data on the health
effects in an urban community adds valuable insight. Additionally, most of the literature focuses
on animal feeding operations, paper mills, and geothermal fields. Hence, data on exposure from
oil refineries also expands on the literature because there are multiple oil refineries in the South
Bay communities. In this study, we focus on the chronic low levels of H2S that continued to
burden the South Bay communities after the odor event. Specifically, we evaluated the
effectiveness of personal- and household-level protective actions by analyzing self-reported
survey data and estimates of individual H2S exposure.

6
Chapter Two: Methods
Study Design and Inclusion Criteria
We partnered up with community organizations and attended community events to recruit
participants. To be eligible to participate, participants needed to be 18 years old and older, fluent
in Spanish or English, and live in Carson, CA, or surrounding neighborhoods. We administered
questionnaires in person between December 6th, 2022, and November 14th, 2023. This study
was approved by the University of Southern California Institutional Review Board, and informed
consent was obtained from each participant prior to participation.
Questionnaire
Participants indicated in the questionnaire how often they experienced the following 22
symptoms in the last month: eye irritation, nose irritation, nosebleeds, dizziness, fatigue,
headaches, vomiting, diarrhea, rash, ringing in the ears, seizures, chest tightness, runny nose,
sore throat, muscle ache, burning eyes, nausea, difficulty sleeping, difficulty breathing, increased
tearing, loss of balance, and difficulty concentrating. The responses were recategorized into
binary variables indicating whether participants experienced each symptom during the last
month. Participants were also asked if they took any of the following actions in the previous
month due to outdoor odors: closed windows, used air purifiers, avoided spending time outside,
and avoided walking, running, exercising, or playing sports outside.
Exposure Modeling
For each participant, we averaged the estimated daily H2S concentrations for the month
the participant completed the survey using their home address. H2S concentrations were
estimated using an Extreme Gradient Boosting (XGBoost) model integrating data from 12
monitors measuring H2S across Los Angeles County. XGBoost leverages machine learning

7
algorithms to improve testing performance. Important variables that contributed to the model
included wind speed, humidity, distance to the channel, distance to the nearest oil refinery,
monthly oil production within 2 kilometers, number of odor complaints, distance to a wastewater
treatment facility, and enhanced vegetation index.
Statistical Analysis
We conducted three sets of analyses to evaluate the relationship between reported
symptoms and H2S, as well as how protective actions affect those associations. For the first set of
analyses, we conducted binary logistic regressions for the 22 symptoms to assess the associations
between H2S exposure and health symptoms after adjusting for sex, age, and current smoking
status. In the second set of analyses, we added each protective action to the model independently
to evaluate the impact of H2S exposure on health symptoms when adjusted for the protective
actions, sex, age, and current smoking status. Lastly, to assess the interaction between H2S
exposure and each protective action, we conducted binary logistic regressions for each of the 22
symptoms and included interaction terms between average H2S and protective action. We also
adjusted for sex, age, and current smoking status for the models with interaction terms and
repeated these analyses for each of the four protective actions. We conducted binary logistic
regression using the binomial generalized linear model (GLM) with the logit link function for all
regressions.
We visually assessed log-linearity by plotting residuals versus continuous variables, and
to evaluate multicollinearity, we calculated variance inflation factors (VIFs). We determined that
there were no violations of the logistic regression assumptions. We evaluated model fit and
identified potential influential points using Cook’s Distance. We also examined standardized
residuals and leverage values. After revising any potential influential points, we kept outliers in

8
the model as there were no signs of erroneous observations. The analyses were performed in
RStudio version 2023.12.1+402.

9
Chapter Three: Results
Descriptive Statistics
In the study, 288 participants completed most or all of the questionnaire. Eight
participants did not respond to the question about their current smoking status (Table 1). For
each of the 22 symptoms, four to eight participants did not respond (Table 2). 18 participants
were excluded from the regression analyses due to either missing or incomplete address
information, which prevented H2S estimation, or because they were determined to be outside the
study area. If participants had missing data for any of the variables in a given model, they were
excluded from that model. Every participant responded to the sex, age, and protective action
questions.
The median estimated H2S concentration of participants during the month of survey
completion was 0.29 ppb (IQR: 0.15 ppb). 79.2% of respondents identified as female and 20.8%
identified as male. Only 2.8% of respondents were current smokers. The median age of
respondents was 49 years (IQR: 22). 74.3% of respondents identified as Latino/Hispanic, 14.9%
as White, 5.9% as Black, 2.1% as Asian, 1.0% as American Indian, 0.3% as Native Hawaiian or
Pacific Islander, and 0.3% as Middle Eastern or North African. As shown in Table 1, 80.9% of
participants reported closing their windows in the last month due to outdoor odors. 58.0%
avoided spending time outside, 47.2% avoided outdoor exercise, and 41.3% used an air purifier
to protect themselves from outdoor odors.
As shown in Table 2, more than half of participants reported experiencing eye irritation
(63.5%), headaches (64.9%), nose irritation (54.5%), runny nose (51.0%), fatigue (57.6%),
muscle aches (58.3%), difficulty sleeping (58.0%) during the month prior to their participation.

10
Slightly less than half reported nose bleeds (42.7%), burning eyes (42.4%), dizziness (42.7%),
sore throat (46.5%), and difficulty concentrating (40.3%).
Association Between Health Symptoms and H2S Exposure
When adjusted for age, sex, and current smoking status, the adjusted odds of
experiencing nosebleeds increase by 1.41 for every 0.1 ppb increase in H2S exposure (95% CI:
1.03 - 1.93; p = 0.03). For every 0.1 ppb increase in H2S exposure, the adjusted odds of
experiencing a runny nose increase by 1.32 times (95% CI: 1.03 - 1.71; p = 0.03), the odds of
experiencing a sore throat increase by 1.50 times (95% CI: 1.17 - 1.96; p < 0.01), and the odds of
having difficulty concentrating increases by 1.34 times (95% CI: 1.05 - 1.72; p = 0.02).
However, the adjusted odds of reporting ringing in the ears decrease by 25% for every 0.1 ppb
increase in H2S exposure (95% CI: 0.58 - 0.97; p = 0.03). As detailed in Table 2, all other
symptoms did not have a statistically significant association with H2S exposure when adjusted
for age, sex, and current smoking status.
Impact of Adding Protective Actions to the Health Symptoms and H2S Exposure Models
As shown in Table 3, adding whether participants closed their windows as a covariate did
not substantially affect the associations between H2S exposure and the health symptoms. Adding
air purifier use to the model reduced the adjusted odds ratio for the association between H2S
exposure and experiencing a runny nose by 3.79% (from 1.32 to 1.27). However, this adjustment
also made the association between H2S exposure and runny nose no longer statistically
significant. The addition of the air purifier variable did not substantially affect any other
associations (Table 4). Tables 5 and 6 show that adding whether participants avoided outside or
avoided exercise outside as a covariate did not considerably affect the associations between H2S
exposure and the health symptoms.

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Interactions Between H2S Exposure and Protective Actions
For the model evaluating chest tightness, the interaction between H2S concentration and
closing windows was statistically significant (OR = 0.41; 95% CI: 0.19 - 0.81; p = 0.01),
indicating that the effect of H2S concentration on the likelihood of reporting chest tightness
slightly differed depending on whether participants closed their windows to protect themselves
from outdoor odors in the previous month. When participants did not close their windows due to
odors outside, the adjusted odds of reporting chest tightness increased 1.75 times for every 0.1
ppb increase in H2S concentration (95% CI: 0.94 - 3.25; p = 0.08). When participants closed their
windows, the adjusted odds of reporting chest tightness decreased by 29% for every 0.1 ppb
increase in H2S concentration (95% CI: 0.28 - 1.82; p = 0.48). However, the association between
chest tightness and H2S adjusted by sex, age, and current smoking status is not statistically
significant when stratified by whether participants close their windows to avoid outdoor odors.
As shown in Table 7, a similar statistically significant interaction was observed in the
model assessing difficulty breathing (OR = 0.31; 95% CI: 0.14 - 0.61; p < 0.01) and loss of
balance model (OR = 0.41; 95% CI: 0.19 - 0.81; p = 0.01). When participants reported that they
did not close their windows to avoid outdoor odors in the previous month, the adjusted odds of
reporting difficulty breathing increased by 2.41 times for every 0.1 ppb increase in H2S
concentration (95% CI: 1.24 - 4.68; p < 0.01). When they report closing their windows, there is
no statistically significant relationship between H2S concentration and difficulty breathing (OR =
0.73; 95% CI: 0.27 - 1.99; p = 0.54). Likewise, when participants report closing their windows
due to outdoor odors, the association between H2S concentration and loss of balance is not
statistically significant (OR = 0.90; 95% CI: 0.34 - 2.35; p = 0.83). In contrast, there is a
statistically significant relationship between H2S concentration and loss of balance when

12
participants report not closing their windows due to the odors during the previous month (p =
0.02). The adjusted odds of reporting a loss of balance increase by 2.21 times for every 0.1 ppb
increase in H2S concentration (95% CI: 1.16 - 4.19). The rest of the interaction terms between
H2S concentration and closing windows due to outdoor odors in the previous months were not
statistically significant (Table 7).
Using air purifiers in response to outdoor odors significantly modified the association
between H2S concentration and reporting burning eyes (OR = 2.03; 95% CI: 1.19 - 3.55; p =
0.01). When stratified, the association between H2S concentration and burning eyes is not
statistically significant among those who used air purifiers in the previous month (OR = 1.35;
95% CI: 0.69 - 2.63; p = 0.37). For those who did not use air purifiers, the adjusted odds of
reporting burning eyes decreased by 0.67 times for every 0.1 ppb increase in H2S concentration
(95% CI: 0.45- 0.98, p = 0.04). The interaction between using air purifiers in response to outdoor
odors and H2S concentration was also statistically significant for the model evaluating increased
tearing (OR = 1.78; 95% CI: 1.06-3.06; p = 0.01). After stratifying by air purifier use, there was
no statistically significant association between H2S concentration and increased tearing in either
air purifier users (OR = 1.59, 95% CI: 0.84 - 3.01, p = 0.15) or non-users (OR = 0.89, 95% CI:
0.62 – 1.28, p = 0.55).
The effect of H2S concentration was significantly modified by whether air purifiers were
used for the model assessing muscle aches (OR = 1.79; 95% CI: 1.04 - 3.18; p = 0.04). When
stratified for the use of air purifiers during the previous month, there is not a statistically
significant association between H2S concentration and muscle aches for either those who report
using air purifiers (OR = 1.46; 95% CI: 0.76 - 2.80; p = 0.26) or those who do not (OR= 0.82;

13
95% CI: 0.58 - 1.14; p = 0.24). The other interaction terms between H2S concentration and using
air purifiers to address outdoor odors during the previous month were not statistically significant.
The analysis revealed no significant interactions between H2S concentration and outdoor
avoidance in any of the models. Similarly, none of the interaction terms between avoiding
outdoor exercise and H2S were statistically significant in any models. This suggests that avoiding
being outside and avoiding outdoor exercise because of odor does not significantly modify the
association between H2S concentration and the reported health symptoms studies.

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Chapter Four: Discussion
Summary of Findings
When adjusted for sex, age, and smoking status, we observed a statistically significant
positive association between average monthly estimated ambient H2S concentrations and nose
bleeds, runny nose, sore throat, and difficulty concentrating. However, we observed a
statistically significant negative association between H2S concentrations and ringing in the ears.
The effect of H2S concentration on the likelihood of reporting chest tightness, difficulty
breathing, or loss of balance differed depending on whether participants closed their windows to
protect themselves from outdoor odors in the previous month. Similarly, the effect of the
likelihood of reporting burning eyes, increased tearing, and muscle aches differed based on
whether participants used an air purifier in response to outdoor odors. When participants did not
close their windows due to outdoor odors in the last month, for every 0.1 ppb increase in H2S
concentration, the odds of reporting difficulty breathing and loss of balance increased.
Unexpectedly, there was a decrease in the odds of experiencing burning eyes for every 0.1 ppb
increase in H2S concentration for those who reported not using air purifiers when there were
outdoor odors. Overall, there was no protective action that significantly decreased the odds of
experiencing health symptoms.
Comparison with Other Studies
The average monthly estimated ambient H2S concentrations near our participants’ homes
were considerably lower than in other studies looking at the health effects of chronic low-level
exposure to H2S in community settings. However, the observed positive associations between
H2S concentrations and health symptoms are consistent with the literature. A study looking at the
health effects of chronic low-level exposure to H2S found that exposed communities have higher

15
odds of experiencing loss of balance and shortness of breath than non-exposed communities
(Legator et al., 2001). Another community-based study found that residential areas near
industrial hog farms had higher rates of sinus problems, breathing difficulty, runny nose, and
scratchy throat than unexposed areas (Bullers, 2005). Similarly, people who live near H2Semitting manure lagoons and hog confinement buildings were found to have significantly higher
levels of reporting loss of balance and loss of concentration than people living in unexposed
areas (Kilburn, 2012).
A Finnish study assessing acute health effects of H2S emissions from a pulp mill found a
significantly higher probability of nasal symptoms and breathlessness when daily average
emissions ranged from 24–30 ppb, compared to a low exposure in another two-day reference
period with the daily average of 0.07–2.4 ppb (Haahtela et al., 1995). Although the
concentrations in our study were lower than the average concentrations during the reference
period, our study also suggests that there is a significant association between nasal symptoms
and difficulty breathing and H2S exposure, suggesting the manifestation of these symptoms at
lower concentrations.
In contrast to our findings, previous studies have reported either a positive association
between H2S exposure and burning eyes or no significant association at all (Buller, 2005;
Haahtela et al., 1995; Schinasi et al., 2011). While no studies assessing low-level H2S exposure
have found an association with ringing in the ears, one study did report higher rates of plugged or
popping ears for exposed participants (Buller, 2005). However, no previous studies have found a
negative association like we did, suggesting that other unaccounted factors may have led to a
false negative association. Although previous studies assessed areas with higher H2S
concentrations than we did, the results are overall consistent with their findings. Multiple other

16
community studies found significant associations between H2S exposure and health symptoms
such as headaches, nausea, fatigue, difficulty sleeping, dizziness, loss of balance, and cough—for
which we did not find a significant association (Jaakkola et al. 1990; Kilburn, 2012; Legator et
al., 2001; Schinasi et al., 2011). This suggests that many health symptoms may only manifest at
higher concentrations of H2S than present in our study area.
Implications of Results
The results of this study suggest that there may be health effects at lower concentrations
than previously studied. The absence of significant reductions in experiencing health symptoms
when taking protective actions suggests that individual- and household-level may not be
effective at very low concentrations. There are no studies evaluating how taking personal
protective actions can reduce H2S-associated symptoms, making it harder for people to find
information on how to protect themselves. During the H2S emergency in Carson, residents
reported struggling to receive information from the local governments and felt like the lack of
clear guidelines made them susceptible to misinformation (Quist et al., 2024). The lack of
information and guidance made residents feel powerless, stressed, and fearful (Quist et al.,
2024). The study did not produce results that can suggest guidelines, but it does highlight areas
for potential future research.
Strengths and Limitations
The study's strengths include the assessment of various health symptoms and protective
actions, as well as the modeled H2S concentrations supported by Los Angeles’ extensive network
of 12 H2S monitors. However, the demographic composition of the participants does not
accurately represent Carson, CA, and the surrounding communities. There was an
overrepresentation of Latino participants, and an underrepresentation of Asian and Black

17
participants compared to the U.S. Census data on Carson. Additionally, 79.2% of our participants
were women, which is very disproportionate to the gender distribution in those communities
(U.S. Census Bureau, n.d.). We were able to address the gender distribution disparity by
adjusting for sex.
Since all analyses relied on self-reported questionnaire data, the results are susceptible to
information bias. The participants were asked to recall symptoms from the last month, which
may minimize recall bias compared to asking about more distant events. However, some
participants may have reported protective action they took during the 2021 odor rather than
within the last month, as the instructions stating the time frame were separated from the question,
potentially leading to confusion. Additionally, participants who reported taking protective
actions because of odors may have also been more sensitive and aware of the odors. Studies have
found that increased annoyance and perception of odors are associated with higher reporting of
health symptoms (Luginaah et al., 2002; Radon et al., 2007; Schinasi et al., 2011). If participants
had an especially unpleasant experience during the 2021 odor event, it may have biased how they
answered these questions. In these analyses, we did not consider the frequency or the severity of
the health symptoms. A deeper analysis of the protective actions, looking at the frequency and
the type of air purifier used, may be beneficial. Additionally, the small sample size may have
limited analyses involving variables with categories that had low response rates.
Using the XGBoost method to estimate participants' H2S exposure has some limitations.
We only used participants' home addresses to evaluate their potential exposure, which may not
be accurate for people who work outside in a different area or spend a substantial amount of time
outdoors away from their homes. It will also not be accurate for participants who are exposed to
high levels of H2S through their occupation. We averaged the estimated daily H2S concentrations

18
for the month the participant completed the survey, which may differ from the maximum H2S
concentrations. There was also very little variation in the individual H2S concentrations
estimates, which may indicate limitations with our modeling or recruitment methods. Although
there are limitations to our method of estimating participants' H2S exposure, it is still a more
robust method than using the distance to an emission source, especially in communities with
multiple H2S pollution sources.

19
Chapter Five: Conclusion
The results of this study suggest that there may be health effects at lower concentrations
of H2S than previously studied. The lack of significant health symptom reductions when taking
protective actions suggests that individual- and household-level may not be effective at very low
concentrations. This emphasizes the importance of strengthening the regulations on the
emissions of H2S. The effectiveness of individual- and household-level protective actions against
H2S exposure needs further study to create guidelines for emergency events and chronic lowlevel exposure. However, the responsibility should not be solely on community members to
protect themselves from polluting sources.

20
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25
Appendix A
Table 1
Characteristics of Participants
Characteristic Number of Respondents (Percent)
Sex (Female) 228 (79.2)
Race/Ethnicity
American Indian 3 (1.0)
Asian 6 (2.1)
Black/African American 17 (5.9)
Latino/Hispanic 214 (74.3)
Middle Eastern or North African 1 (0.3)
White/Caucasian 43 (14.9)
Native Hawaiian or Pacific Islander 1 (0.3)
Race/Ethnicity Not Listed 1 (0.3)
Not reported 2 (0.7)
Employment
Employed full time 60 (20.8)
Employed part-time 55 (19.1)
Unemployed – seeking work 39 (13.5)
Unemployed – retired 40 (13.9)
Unemployed – homemaker 69 (24.0)
Unemployed – disabled 3 (1.0)
Unemployed – student 12 (4.2)
Not reported 10 (3.5)
Current smoker a 8 (2.8)
Closed windows 233 (80.9%)
Used air purifier 119 (41.3%)
Avoided spending time outside 167 (58.0%)
Avoided exercise outdoors 136 (47.2%)
Age (median, IQR)a 49 (22)
Average H2S concentration in parts per billion (ppb) (median, IQR) 0.29 (0.15)
Total Participants 288
a 8 non-responses

26
Table 2
Effect of 0.1 ppb Increase in H2S Concentrations on Health Symptoms Adjusted for Age, Sex, and
Current Smoking Status
Symptoms Number of participants
(Percent)
OR (95 CI%) P
Neurological Dizziness
No
Yes
Not reported
161 (55.9)
123 (42.7)
4 (1.4)
0.89 (0.7 - 1.14) 0.36
Headaches
No
Yes
Not reported
96 (33.3)
187 (64.9)
5 (1.7)
1.18 (0.9 - 1.56) 0.24
Seizure
No
Yes
Not reported
272 (94.4)
8 (2.8)
8 (2.8)
0.92 (0.38 - 1.92) 0.83
Nausea
No
Yes
Not reported
201 (69.8)
80 (27.8)
7 (2.4)
0.95 (0.72 - 1.23) 0.70
Loss of balance
No
Yes
Not reported
196 (68.1)
84 (29.2)
8 (2.8)
1.07 (0.82 - 1.4) 0.60
Difficulty concentrating
No
Yes
Not reported
167 (58.0)
116 (40.3)
5 (1.7)
1.34 (1.05 - 1.72) 0.02*
Ringing in the ears
No
Yes
Not reported
173 (60.1)
110 (38.2)
5 (1.7)
0.75 (0.58 - 0.97) 0.03*

27
Symptoms Number of participants
(Percent)
OR (95 CI%) P
Ocular Eye irritation
No
Yes
Not reported
98 (34.0)
183 (63.5)
7 (2.4)
1.23 (0.95 - 1.62) 0.13
Burning eyes
No
Yes
Not reported
159 (55.2)
122 (42.4)
7 (2.4)
1.00 (0.78 - 1.28) 1.00
Increased tearing
No
Yes
Not reported
254 (88.2)
28 (9.7)
6 (2.1)
1.22 (0.96 - 1.56) 0.11
Respiratory Nose irritation
No
Yes
Not reported
125 (43.4)
157 (54.5)
6 (2.1)
1.25 (0.98 - 1.62) 0.08
Nosebleeds
No
Yes
Not reported
161 (55.9)
123 (42.7)
4 (1.4)
1.41 (1.03 - 1.93) 0.03*
Runny nose
No
Yes
Not reported
134 (46.5)
147 (51.0)
7 (2.4)
1.32 (1.03 - 1.71) 0.03*
Chest tightness
No
Yes
Not reported
211 (73.3)
70 (24.3)
7 (2.4)
0.87 (0.65 - 1.15) 0.34
Sore throat
No
Yes
Not reported
148 (51.4)
134 (46.5)
6 (2.1)
1.50 (1.17 - 1.96) <0.01*
Difficulty breathing
No
Yes
Not reported
202 (70.1)
78 (27.1)
8 (2.8)
0.95 (0.72 - 1.24) 0.71

28
Symptoms Number of participants
(Percent)
OR (95 CI%) P
Well-being Fatigue
No
Yes
Not reported
115 (39.9)
166 (57.6)
7 (2.4)
1.19 (0.92 - 1.54) 0.19
Difficulty sleeping
No
Yes
Not reported
116 (40.3)
167 (58.0)
5 (1.7)
1.13 (0.89 - 1.46) 0.32
Gastrointestina
l
Vomiting
No
Yes
Not reported
254 (88.2)
28 (9.7)
6 (2.1)
0.85 (0.54 - 1.27) 0.44
Diarrhea
No
Yes
Not reported
224 (77.8)
58 (20.1)
6 (2.1)
1.02 (0.76 - 1.36) 0.89
Muscular Muscle ache
No
Yes
Not reported
224 (77.8)
58 (20.1)
6 (2.1)
1.07 (0.83 - 1.38) 0.61
Dermatologica
l
Rash
No
Yes
Not reported
238 (82.6)
42 (14.6)
8 (2.8)
1.02 (0.72 - 1.4) 0.93
* Indicates statistical significance at the alpha level of 0.05 (p<0.05)

29
Table 3
Effect of 0.1 ppb Increase in H2S Concentrations on Health Symptoms Adjusted for Window
Closure, Age, Sex, and Current Smoking Status
Symptoms OR (95 CI%) P
Neurological Dizziness 0.89 (0.7 - 1.14) 0.36
Headaches 1.17 (0.89 - 1.54) 0.27
Seizure 0.96 (0.4 - 1.98) 0.91
Nausea 0.93 (0.7 - 1.21) 0.59
Loss of balance 1.08 (0.82 - 1.41) 0.38
Difficulty concentrating 1.32 (1.04 - 1.7) 0.03*
Ringing in the ears 0.75 (0.57 - 0.96) 0.03*
Ocular Eye irritation 1.22 (0.94 - 1.6) 0.15
Burning eyes 0.97 (0.75 - 1.24) 0.82
Increased tearing 1.20 (0.94 - 1.54) 0.15
Respiratory Nose irritation 1.23 (0.96 - 1.59) 0.11
Nosebleeds 1.40 (1.02 - 1.93) 0.04*
Runny nose 1.30 (1.02 - 1.69) 0.04*
Chest tightness 0.87 (0.65 - 1.14) 0.33
Sore throat 1.50 (1.16 - 1.95) <0.01*
Difficulty breathing 0.95 (0.72 - 1.23) 0.07
Well-being Fatigue 1.19 (0.92 - 1.55) 0.18
Difficulty sleeping 1.12 (0.87 - 1.44) 0.38
Gastrointestinal Vomiting 0.84 (0.53 - 1.26) 0.42
Diarrhea 0.96 (0.7 - 1.29) 0.93
Muscular Muscle ache 1.01 (0.75 - 1.35) 0.65
Dermatological Rash 0.98 (0.68 - 1.37) 0.90
* Indicates statistical significance at the alpha level of 0.05 (p<0.05)

30
Table 4
Effect of 0.1 ppb Increase in H2S Concentrations on Health Symptoms Adjusted for Air Purifier
Use, Age, Sex, and Current Smoking Status
Symptoms OR (95 CI%) P
Neurological Dizziness 0.87 (0.68 - 1.11) 0.26
Headaches 1.12 (0.85 - 1.49) 0.43
Seizure 0.88 (0.36 - 1.88) 0.77
Nausea 0.88 (0.66 - 1.15) 0.36
Loss of balance 1.07 (0.82 - 1.4) 0.61
Difficulty concentrating 1.30 (1.01 - 1.67) 0.04*
Ringing in the ears 0.73 (0.55 - 0.94) 0.02*
Ocular Eye irritation 1.18 (0.9 - 1.55) 0.24
Burning eyes 0.95 (0.74 - 1.22) 0.69
Increased tearing 1.17 (0.91 - 1.51) 0.21
Respiratory Nose irritation 1.18 (0.91 - 1.54) 0.21
Nosebleeds 1.40 (1.02 - 1.92) 0.04*
Runny nose 1.27 (0.99 - 1.65) 0.06
Chest tightness 0.85 (0.63 - 1.12) 0.26
Sore throat 1.46 (1.13 - 1.91) <0.01*
Difficulty breathing 0.92 (0.7 - 1.2) 0.55
Well-being Fatigue 1.13 (0.87 - 1.47) 0.38
Difficulty sleeping 1.02 (0.79 - 1.33) 0.86
Gastrointestinal Vomiting 0.84 (0.53 - 1.26) 0.41
Diarrhea 0.96 (0.7 - 1.29) 0.78
Muscular Muscle ache 1.02 (0.79 - 1.33) 0.86
Dermatological Rash 0.97 (0.68 - 1.35) 0.85
* Indicates statistical significance at the alpha level of 0.05 (p<0.05)

31
Table 5
Effect of 0.1 ppb Increase in H2S Concentrations on Health Symptoms Adjusted for Outdoor
Avoidance, Age, Sex, and Current Smoking Status
Symptoms OR (95 CI%) P
Neurological Dizziness 0.89 (0.70 - 1.13) 0.36
Headaches 1.18 (0.90 - 1.56) 0.24
Seizure 0.91 (0.4 - 1.87) 0.81
Nausea 0.95 (0.72 - 1.23) 0.69
Loss of balance 1.08 (0.82 - 1.41) 0.59
Difficulty concentrating 1.35 (1.05 - 1.74) 0.02*
Ringing in the ears 0.75 (0.57 - 0.96) 0.03*
Ocular Eye irritation 1.22 (0.94 - 1.61) 0.14
Burning eyes 1.00 (0.78 - 1.28) 0.99
Increased tearing 1.22 (0.95 - 1.56) 0.11
Respiratory Nose irritation 1.25 (0.98 - 1.62) 0.08
Nosebleeds 1.42 (1.03 - 1.96) 0.03*
Runny nose 1.33 (1.03 - 1.73) 0.03*
Chest tightness 0.87 (0.65 - 1.15) 0.34
Sore throat 1.51 (1.17 - 1.97) <0.01*
Difficulty breathing 0.95 (0.72 - 1.24) 0.71
Well-being Fatigue 1.18 (0.92 - 1.54) 0.20
Difficulty sleeping 1.13 (0.88 - 1.46) 0.34
Gastrointestinal Vomiting 0.85 (0.55 - 1.27) 0.45
Diarrhea 1.02 (0.76 - 1.36) 0.90
Muscular Muscle ache 1.07 (0.83 - 1.37) 0.62
Dermatological Rash 1.01 (0.71 - 1.42) 0.93
*Indicates statistical significance at the alpha level of 0.05 (p<0.05)

32
Table 6
Effect of 0.1 ppb Increase in H2S Concentrations on Health Symptoms Adjusted for Outdoor
Exercise Avoidance, Age, Sex, and Current Smoking Status
Symptoms OR (95 CI%) P
Neurological Dizziness 0.89 (0.70 - 1.13) 0.36
Headaches 1.18 (0.90 - 1.56) 0.24
Seizure 0.91 (0.4 - 1.87) 0.81
Nausea 0.95 (0.72 - 1.23) 0.69
Loss of balance 1.08 (0.82 - 1.41) 0.59
Difficulty concentrating 1.35 (1.05 - 1.74) 0.02*
Ringing in the ears 0.75 (0.57 - 0.96) 0.03*
Ocular Eye irritation 1.22 (0.94 - 1.61) 0.14
Burning eyes 1.00 (0.78 - 1.28) 0.99
Increased tearing 1.22 (0.95 - 1.56) 0.11
Respiratory Nose irritation 1.25 (0.98 - 1.62) 0.08
Nosebleeds 1.42 (1.03 - 1.96) 0.03*
Runny nose 1.33 (1.03 - 1.73) 0.03*
Chest tightness 0.87 (0.65 - 1.15) 0.34
Sore throat 1.51 (1.17 - 1.97) <0.01*
Difficulty breathing 0.95 (0.72 - 1.24) 0.71
Well-being Fatigue 1.18 (0.92 - 1.54) 0.20
Difficulty sleeping 1.13 (0.88 - 1.46) 0.34
Gastrointestinal Vomiting 0.85 (0.55 - 1.27) 0.45
Diarrhea 1.02 (0.76 - 1.36) 0.90
Muscular Muscle ache 1.07 (0.83 - 1.37) 0.62
Dermatological Rash 1.01 (0.71 - 1.42) 0.93
* Indicates statistical significance at the alpha level of 0.05 (p<0.05)

Table 7
Statistical Significance of Interaction Terms Between H2S Concentration and Each Protective Action
Closed Windows Air Purifier Avoided Outside Avoided Outdoor Exercise
Symptoms OR (95 CI%) P OR (95 CI%) P OR (95 CI%) P OR (95 CI%) P
Neurological Dizziness 0.66 (0.35 - 1.21) 0.18 0.95 (0.58 - 1.55) 0.83 1.21 (0.74 - 1.99) 0.45 1.08 (0.66, 1.78) 0.74
Headaches 0.48 (0.19 - 1.02) 0.08 1.34 (0.75 - 2.46) 0.34 0.91 (0.52 - 1.56) 0.73 0.64 (0.36, 1.11) 0.11
Seizure 0.71 (0.14 - 4.15) 0.68 1.38 (0.27 - 8.53) 0.71 0.11 (0.00 - 1.44) 0.18 0.07 (<0.1, 0.77) 0.08
Nausea 1.06 (0.5 - 2.64) 0.89 1.21 (0.68 - 2.21) 0.53 1.17 (0.68 - 2.07) 0.58 1.61 (0.94, 2.85) 0.09
Loss of balance 0.41 (0.19 - 0.81) 0.01* 1.33 (0.77 - 2.32) 0.31 1.15 (0.67 - 2.01) 0.62 0.96 (0.56, 1.65) 0.88
Difficulty
concentrating
0.66 (0.33 - 1.24) 0.21 1.42 (0.86 - 2.38) 0.18 1.30 (0.79 - 2.17) 0.31 1.05 (0.64, 1.74) 0.85
Ringing in the ears 0.56 (0.29 - 1.05) 0.07 1.48 (0.87 - 2.57) 0.16 1.24 (0.73 - 2.16) 0.43 1.16 (0.69, 1.97) 0.57
Ocular Eye irritation 0.68 (0.31 - 1.33) 0.29 1.21 (0.69 - 2.15) 0.51 1.04 (0.61 - 1.77) 0.89 0.90 (0.52, 1.56) 0.70
33

Closed Windows Air Purifier Avoided Outside Avoided Outdoor Exercise
Symptoms OR (95 CI%) P OR (95 CI%) P OR (95 CI%) P OR (95 CI%) P
Burning eyes 0.83 (0.43 - 1.65) 0.58 2.03 (1.19 - 3.55) 0.01* 1.23 (0.75 - 2.07) 0.41 1.09 (0.66, 1.81) 0.74
Increased tearing 0.79 (0.41 - 1.48) 0.46 1.78 (1.06 - 3.06) 0.03* 1.57 (0.95 - 2.65) 0.08 1.23 (0.75, 2.06) 0.42
Respiratory Nose irritation 0.49 (0.22 - 0.97) 0.06 1.07 (0.63 - 1.85) 0.80 1.15 (0.69 - 1.93) 0.59 0.87 (0.52, 1.46) 0.58
Nosebleeds 1.69 (0.6 - 7.37) 0.38 0.98 (0.52 - 1.86) 0.95 1.44 (0.75 - 2.9) 0.29 1.01 (0.53, 1.95) 0.98
Runny nose 0.5 (0.22 - 1.00) 0.07 1.19 (0.71 - 2.01) 0.51 0.91 (0.54 - 1.51) 0.71 0.76 (0.45, 1.28) 0.30
Chest tightness 0.41 (0.19 - 0.81) 0.01* 1.3 (0.73 - 2.37) 0.38 0.75 (0.42 - 1.32) 0.43 0.74 (0.41, 1.31) 0.30
Sore throat 0.68 (0.31 - 1.33) 0.29 1.52 (0.9 - 2.62) 0.12 0.95 (0.57 - 1.6) 0.43 0.95 (0.56, 1.61) 0.83
Difficulty
breathing
0.31 (0.14 - 0.61) <0.01
*
1.12 (0.65 - 1.95) 0.69 0.82 (0.48 - 1.39) 0.45 0.88 (0.51, 1.51) 0.65
Well-being Fatigue 0.83 (0.41 - 1.56) 0.57 1.29 (0.76 - 2.24) 0.35 1.21 (0.72 - 2.04) 0.47 1.01 (0.6, 1.71) 0.96
34

Closed Windows Air Purifier Avoided Outside Avoided Outdoor Exercise
Symptoms OR (95 CI%) P OR (95 CI%) P OR (95 CI%) P OR (95 CI%) P
Difficulty sleeping 0.66 (0.33 - 1.23) 0.21 1.3 (0.78 - 2.19) 0.32 1.37 (0.83 - 2.29) 0.23 1.58 (0.94, 2.73) 0.09
Gastrointestinal Vomiting 0.49 (0.18 - 1.37) 0.15 1.26 (0.54 - 3.06) 0.60 0.69 (0.29 - 1.60) 0.39 0.82 (0.34, 1.93) 0.66
Diarrhea 0.52 (0.24 - 1.07) 0.08 0.92 (0.5 - 1.73) 0.79 0.68 (0.37 - 1.22) 0.20 0.69 (0.37, 1.24) 0.22
Muscular Muscle ache 1.02 (0.54 - 1.89) 0.96 1.79 (1.04 - 3.18) 0.04* 1.62 (0.97 - 2.76) 0.07 1.14 (0.68, 1.93) 0.63
Dermatological Rash 1.04 (0.31 - 6.09) 0.95 1.94 (0.93 - 4.34) 0.09 0.75 (0.37 - 1.56) 0.43 1.13 (0.57, 2.31) 0.73
Note: All the models assessed the effect of H2S exposure on health symptoms adjusted for the protective action, age, sex, and current
smoking status. Each model included an interaction term between each protective action and hydrogen sulfide concentrations. The
odds ratios and p-values shown above are for the interaction terms. Results are presented as the change per 0.1 ppb increase in
hydrogen sulfide concentrations.
* Indicates statistical significance at the alpha level of 0.05 (p<0.05)
3
5

Abstract (if available)

Abstract Oil refineries and wastewater treatment facilities expose residents of Carson, California, and surrounding communities to chronic low levels of hydrogen sulfide (H2S). We conducted community-based questionnaires and modeled H2S exposure to assess the health effects of low H2S concentrations and the effectiveness of personal- and household-level protective actions. The median estimated H2S concentration of participants during the month of survey completion was 0.29 parts per billion (ppb) (IQR: 0.15 ppb). After adjusting for age, sex, and smoking status, every 0.1 ppb increase in H2S exposure is associated with 1.41 times higher odds of nosebleeds (95% CI:1.03 - 1.93; p = 0.03), 1.50 times higher odds of a runny nose (95% CI: 1.03 - 1.71; p = 0.03), 1.50 times higher odds of a sore throat (95% CI: 1.17 - 1.96; p < 0.01), and 1.34 times higher odds of difficulty concentrating (95% CI: 1.05 - 1.72; p = 0.02). The effect of H2S concentration on the likelihood of reporting chest tightness (p = 0.01), difficulty breathing (p < 0.01), loss of balance (p = 0.01), burning eyes (p = 0.01), and increased tearing (p = 0.03) differed depending on whether participants closed their windows or used air purifiers to protect themselves from outdoor odors in the previous month. No protective action significantly decreased the odds of experiencing health symptoms once stratified. The results of this study suggest that there may be health effects at lower concentrations of H2S than previously studied. The absence of significant symptom reductions when taking protective actions suggests that individual- and household-level may not be effective at very low concentrations, emphasizing the need for more regulatory and community-level solutions.

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Asset Metadata

Creator Ahumada, Jennifer (author)

Core Title Effectiveness of individual- and household-level protective actions in reducing symptoms associated with hydrogen sulfide chronic low-level exposure

School Keck School of Medicine

Degree Master of Science

Degree Program Applied Biostatistics and Epidemiology

Degree Conferral Date 2024-08

Publication Date 08/27/2024

Defense Date 08/25/2024

Publisher Los Angeles, California (original), University of Southern California (original), University of Southern California. Libraries (digital)

Tag air purifier,health symptoms,hydrogen sulfide,OAI-PMH Harvest,protective actions

Format theses (aat)

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Johnston, Jill (committee chair), Farzan, Shohreh (committee member), Habre, Rima (committee member)

Creator Email jahumada@usc.edu,jenniferaahumada@gmail.com

Permanent Link (DOI) https://doi.org/10.25549/usctheses-oUC113999U1R

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