The disappearing Salton Sea: A critical reflection on the emerging environmental threat of disappearing saline lakes and potential impacts on children's health

Cohort profile: The Assessing Imperial Valley Respiratory Health and the Environment (AIRE) study

BACKGROUND

The Children's Assessing Imperial Valley Respiratory Health and the Environment (AIRE) study is a prospective cohort study of environmental influences on respiratory health in a rural, southeastern region of California (CA), which aims to longitudinally examine the contribution of a drying saline lake to adverse health impacts in children.

OBJECTIVES

This cohort was established through a community-academic partnership with the goal of assessing the health effects of childhood exposures to wind-blown particulate matter (PM) and inform public health action. We hypothesize that local PM sources are related to poorer children's respiratory health.

POPULATION

Elementary school children in Imperial Valley, CA.

DESIGN

Prospective cohort study.

METHODS

Between 2017 and 2019, we collected baseline information on 731 children, then follow-up assessments yearly or twice-yearly since 2019. Data have been collected on children's respiratory health, demographics, household characteristics, physical activity and lifestyle, via questionnaires completed by parents or primary caregivers. In-person measurements, conducted since 2019, repeatedly assessed lung function, height, weight and blood pressure. Exposure to air pollutants has been assessed by multiple methods and individually assigned to participants using residential and school addresses. Health data will be linked to ambient and local sources of PM, during and preceding the study period to understand how spatiotemporal trends in these environmental exposures may relate to respiratory health.

PRELIMINARY RESULTS

Analyses of respiratory symptoms indicate a high prevalence of allergies, bronchitic symptoms and wheezing. Asthma diagnosis was reported in 24% of children at enrolment, which exceeds both CA state and US national prevalence estimates for children.

CONCLUSIONS

The Children's AIRE cohort, while focused on the health impacts of the drying Salton Sea and air quality in Imperial Valley, is poised to elucidate the growing threat of drying saline lakes and wind-blown dust sources to respiratory health worldwide, as sources of wind-blown dust emerge in our changing climate.

Seeking care across the US-Mexico border: The experiences of Latinx and Indigenous Mexican caregivers of children with asthma or respiratory distress

BACKGROUND

Many Latinx and Indigenous Mexican populations in the United States Southwest live in unincorporated communities in the US-Mexico borderlands called colonias. These environmental justice communities often lack basic infrastructure, including healthcare services, prompting many to seek services across the border. However, due to geopolitical factors more vulnerable caregivers are limited to utilize healthcare services in the US. This paper reports the experiences and healthcare decision-making of caregivers living in colonias in the US-Mexico border region who care for children with respiratory health conditions.

METHODS

This study was carried out from September to December 2020. Focus groups and interviews were conducted with Latinx and Indigenous Mexican caregivers of children with asthma or respiratory distress. Qualitative interviews elicited caregivers' perspectives on the environmental factors affecting children's chronic health conditions and use of healthcare services. The analysis employed the concept of structure vulnerability to theorize geography as a structural determinant of health for caregivers faced with making healthcare decisions for their suffering from respiratory health conditions. A survey was administered to collect basic sociodemographic information.

RESULTS

A total of 36 caregivers participated in the study. Structural factors including unincorporated community status and government inaction intersected with social determinants of health to prompt caregivers to cross the US-Mexico border to access healthcare services in Mexico for their children. Yet, more vulnerable caregivers (i.e., those without documentation status in the US) and their children, accessing healthcare services in the US was not an option limiting caregivers' ability to meet their children's healthcare needs. In such cases, geography acts as a structural determinant of health.

CONCLUSION

This study shows the importance of geography in health. Rural unincorporated colonias located in the borderlands are precariously located and lack basic critical infrastructure including healthcare access. Within such places, historically and socially marginalized populations become invisible, are subject to the health effects of environmental hazards, and are limited depending on their positionality and thus vulnerability to healthcare services.

Short-term and repeated exposure to particulate matter sizes from Imperial Valley, California to induce inflammation and asthmatic-like symptoms in mice

Imperial Valley, California has become increasingly hot, dry, and polluted over the past decade. Particulate matter (PM) levels are amongst the highest in this State, associated with significantly higher asthma prevalence among children in the region compared to national and state averages. The present study was performed to test the hypothesis that Imperial Valley PM by size and chemical composition might possess allergenic properties following introduction into murine lungs without prior sensitization to a known allergen with size fraction as a determining factor. In acute exposure experiments, BALB/c male mice were administered a single 50-μl oropharyngeal aspiration of nanopure water (H2O; control) or a stock 1 μg/μl PM solution. In sub-acute exposure experiments, male and female mice were treated with a total of six 16.6-μl intranasal instillations of H2O or stock PM solution over the course of 14 days. In all experiments, pulmonary function tests were performed 24 hr after the final instillation followed by necropsies for the collection of biological samples. Inflammatory responses measured via cellularity in histopathological tissue sections as well as significant, marked influxes of eosinophils and lymphocytes were noted in the bronchoalveolar lavage fluid in mice administered PM compared to control. Allergic responses, including airway hyperresponsiveness and significantly increased expression of IL-1ß, were found in male mice exposed to either PM2.5 or ultrafine (PMUF). A combination of all three size fractions of PM from Imperial Valley initiated atopic and asthmatic-like symptoms in the lungs of mice in the absence of additional allergen or preexisting condition.

Agricultural burning in Imperial Valley, California and respiratory symptoms in children: A cross-sectional, repeated measures analysis

Burning of agricultural fields is an understudied source of air pollution in rural communities in the United States. Smoke from agricultural burning contains air toxics that adversely impact respiratory health. Imperial County in southeastern California is a highly productive agricultural valley that heavily employs agricultural burning to clear post-harvest crop remnants. We related individual-level exposure to agricultural burns to parent-reported respiratory symptoms in children. We leveraged the Children's Assessing Imperial Valley Respiratory Health and the Environment (AIRE) cohort of 735 predominantly Hispanic low-income elementary school students in Imperial County. Parents reported children's respiratory health symptoms and family demographic characteristics in questionnaires collected at enrollment and in annual follow-up assessments from 2017 to 2019. Permitted agricultural burns in Imperial County from 2016 to 2019 were spatially linked to children's geocoded residential addresses. We used generalized estimating equations to evaluate prevalence differences (PDs) in respiratory symptoms with increasing exposure to agricultural burning within 3 km in the 12 months prior to each assessment. Nearly half of children (346, 49 %) lived within 3 km of at least one agricultural burn in the year prior to study enrollment. In adjusted models, each additional day of agricultural burning in the prior year was associated with a one percentage point higher prevalence of wheezing (PD 1.1 %; 95 % CI 0.2 %, 2.0 %) and higher bronchitic symptoms (PD 1.0 %; 95 % CI -0.2 %, 2.1 %). Children exposed to four or more days of burning had an absolute increased prevalence of wheezing and bronchitic symptoms of 5.9 % (95 % CI -0.3 %, 12 %) and 5.6 % (95 % CI -1.8 %, 13 %), respectively, compared to no burn exposure. Associations with wheezing were stronger among children with asthma (PD 14 %; 95 % CI -1.4 %, 29 %). To our knowledge, this is the first U.S. study of agricultural burning and children's respiratory health. This work suggests that reducing agricultural burning could improve children's respiratory health.

Latinx and Indigenous Mexican Caregivers' Perspectives of the Salton Sea Environment on Children's Asthma, Respiratory Health, and Co-Presenting Health Conditions

This research investigated Latinx and Indigenous Mexican caregivers' perspectives of the Salton Sea's environment (e.g., dust concentrations and other toxins) on child health conditions. The Salton Sea is a highly saline drying lakebed located in the Inland Southern California desert borderland region and is surrounded by agricultural fields. Children of Latinx and Indigenous Mexican immigrant families are especially vulnerable to the Salton Sea's environmental impact on chronic health conditions due to their proximity to the Salton Sea and structural vulnerability. From September 2020 to February 2021, we conducted semi-structured interviews and focus groups with a total of 36 Latinx and Indigenous Mexican caregivers of children with asthma or respiratory distress living along the Salton Sea. A community investigator trained in qualitative research conducted interviews in Spanish or Purépecha, an indigenous language spoken by immigrants from Michoacán, Mexico. Template and matrix analysis was used to identify themes and patterns across interviews and focus groups. Participants characterized the Salton Sea's environment as toxic, marked by exposure to sulfuric smells, dust storms, chemicals, and fires, all of which contribute to children's chronic health conditions (e.g., respiratory illnesses such as asthma, bronchitis, and pneumonia, co-presenting with allergies and nosebleeds). The findings have important environmental public health significance for structurally vulnerable child populations in the United States and globally.

The Intersection of Workplace and Environmental Exposure on Health in Latinx Farm Working Communities in Rural Inland Southern California

Workplace and environmental exposures pose health risks for racial/ethnic minorities in rural agricultural communities, placing them at a disadvantage in accessing needed health care. Over three fourths (76%) of the 2.4 million farmworkers in the United States are immigrants, mostly from Mexico. However, little is known of the community health concerns and barriers to care of Latinx farmworkers in inland southern California. This qualitative study used a community-based participatory research approach, conducting nine in-home meetings to obtain meaningful community input on health concerns and barriers to access healthcare services among rural residents of the Eastern Coachella Valley, who are also located near the desert-bound Salton Sea of inland southern California. All interviews were audio-recorded and analyzed via listening to the audio recordings and summarizing data in templates and matrices. Participants discussed health concerns related to agricultural labor, including heat-related illness, musculoskeletal ailments and injuries, skin disorders, respiratory illness, and trauma. Participants raised concerns about environmental exposures related to agriculture and the nearby Salton Sea, a highly saline lakebed, and proposed solutions to improve the health of their communities. The findings from this study suggest farmworkers are aware of the health risks posed by living and working in rural farmlands but lack resources and information to act upon and advocate for improved public health.

Evaluating health outcome metrics and their connections to air pollution and vulnerability in Southern California's Coachella Valley

The ongoing desiccation of California's Salton Sea has led to increasing concerns about air quality and health for its surrounding communities, including the nearby Coachella Valley - a region already experiencing severe air quality and health disparities. Here we explore spatial air pollution and human health disparities in the Coachella Valley with particular attention to disparities arising across population characteristics including both socioeconomic and demographic vulnerabilities. We use two different measures of respiratory and cardiovascular health outcomes at the individual and census tract levels - one measure based on a randomly sampled telephone survey and the other measure based on emergency room visitation data - to investigate the degree to which these health outcomes are connected to air pollution and socioeconomic metrics. We further investigate biases and differences between the health outcome metrics themselves and suggest opportunities to address them in future analyses and survey efforts. We find that more vulnerable communities are associated with higher levels of fine particulates, but lower levels of ozone. While emergency visit rates show a significant positive correlation with both pollutants, no such association is found when using surveyed health outcome data. The ratio of emergency visits versus survey rates shows a positive relationship with socioeconomic and demographic vulnerability, indicating that vulnerable communities are less likely to self-report diagnoses despite higher rates of respiratory or cardiovascular hospitalization. Additionally, survey respondents tend to show less vulnerability relative to their surrounding census-based demographics. These findings suggest the need for greater attention to health issues specifically within disadvantaged communities in the Coachella Valley, building upon and working within existing community networks and local resources, to better address current and projected health needs. Our findings also highlight disparities in air pollution exposure, health outcomes, and population characteristics in the Coachella Valley, providing context for crucial pollution reduction efforts in the face of increasing environmental threats.

Lung Inflammatory Response to Environmental Dust Exposure in Mice Suggests a Link to Regional Respiratory Disease Risk

PURPOSE

The Salton Sea, California's largest lake, is designated as an agricultural drainage reservoir. In recent years, the lake has experienced shrinkage due to reduced water sources, increasing levels of aerosolized dusts in surrounding regions. Communities surrounding the Salton Sea have increased asthma prevalence versus the rest of California; however, a connection between dust inhalation and lung health impacts has not been defined.

METHODS

We used an established intranasal dust exposure murine model to study the lung inflammatory response following single or repetitive (7-day) exposure to extracts of dusts collected in regions surrounding the Salton Sea (SSDE), complemented with in vitro investigations assessing SSDE impacts on the airway epithelium.

RESULTS

In these investigations, single or repetitive SSDE exposure induced significant lung inflammatory cytokine release concomitant with neutrophil influx. Repetitive SSDE exposure led to significant lung eosinophil recruitment and altered expression of genes associated with allergen-mediated immune response, including Clec4e. SSDE treatment of human bronchial epithelial cells (BEAS-2B) induced inflammatory cytokine production at 5- and 24-hours post-treatment. When BEAS-2B were exposed to protease activity-depleted SSDE (PDSSDE) or treated with SSDE in the context of protease-activated receptor-1 and -2 antagonism, inflammatory cytokine release was decreased. Furthermore, repetitive exposure to PDSSDE led to decreased neutrophil and eosinophilic influx and IL-6 release in mice compared to SSDE-challenged mice.

CONCLUSION

These investigations demonstrate potent lung inflammatory responses and tissue remodeling in response to SSDE, in part due to environmental proteases found within the dusts. These studies provide the first evidence supporting a link between environmental dust exposure, protease-mediated immune activation, and respiratory disease in the Salton Sea region.

Use of trajectory models to track air pollution from source to exposure: A methodological approach for identifying communities at risk

OBJECTIVE

Ongoing environmental changes increasingly require public health nurses to understand how environmental factors impact the health of populations. One approach to researching these impacts is incorporating environmental research methods to determine associations between harmful exposures and health. We use the Salton Sea in Southern California as a demonstration of how environmental exposure can be examined using air parcel trajectory analysis.

DESIGN

We demonstrate a methodology for public health nurses to better understand and apply data from the Hybrid Single-Particle Lagrangian Integrated Trajectory meteorological model to estimate the effect of airborne particulate matter from a single source.

MEASUREMENTS

We explain a method for tracking air parcel trajectories to populations: selection of meterological data to identify air parcels, geographic identification of population centers, generation of trajectories, classification of trajectory dispersions, adjusting for atmospheric stability, and merging environmental variables with health data.

CONCLUSIONS

Climate change-related environmental events are expected to become more commonplace and disproportionately affect those populations impacted by health disparities. Public health nurses can identify communities at risk so that public health nursing researchers can use these techniques in collaboration with environmental science to robustly examine health effects of proximal air pollution sources for communities at risk.

Differential inflammatory potential of particulate matter (PM) size fractions from Imperial Valley, CA

Particulate matter (PM) in Imperial Valley originates from a variety of sources such as agriculture, traffic at the border crossing, emissions from the cross-border city of Mexicali, and the drying lakebed of the Salton Sea. Dust storms in Imperial Valley, California regularly lead to exceedances of the federal air quality standards for PM10 (diameter less than 10 microns). To determine if there are differences in the composition and biological response to Imperial County PM by size, ambient PM samples were collected from a sampling unit stationed in the northern-most part of the valley, South of the Salton Sea. Ultrafine, fine, and coarse PM samples were collected and extracted separately. Chemical composition of each size fraction was obtained after extraction by using several analytical techniques, and biological response was measured by exposing a cell line of macrophages to particles and quantifying subsequent gene expression. Biological measurements demonstrated coarse PM induced an inflammatory response in macrophages measured in increases of inflammatory markers IL-1β, IL-6, IL-8 and CXCL2 expression, whereas ultrafine and fine PM only demonstrated significant increases in expression of CYP1a1. These differential responses were due not only to particle size, but to the distinct chemical profiles of each size faction as well. Community groups in Imperial Valley have already completed several projects to learn more about local air quality, giving residents access to data that provides real-time levels of PM2.5 and PM10 as well as recommendations on health-based practices dependent on the current AQI (air quality index). However, to date there is no information on the composition or toxicity of ambient PM from the region. The data presented here could provide more definitive information on the toxicity of PM by size, and further inform the community on local air quality.

The Disappearing Lake: A Historical Analysis of Drought and the Salton Sea in the Context of the GeoHealth Framework

The Imperial Valley region of Southeastern California has become one of the most productive agricultural regions in the state and has the highest rates of childhood asthma in California. Lack of precipitation in the Imperial Valley has caused the water level of the Salton Sea to recede to a record low since its formation in the early 1900s. Previous studies of wind and dust deposition conducted in other regions have shown how reduced precipitation, ground heating, and the diminishing water level in an arid climate pose a risk of exposing previously sequestered toxic chemicals to open air, adversely affecting lung health. The purpose of this study is to draw historical parallels between the Aral Sea and Salton Sea in the context of geomorphology, ecology, human health, economics, and human migration, to inform an assessment of environmentally related health impacts of those living in the Imperial Valley region. Future droughts and heatwaves are expected to rise in frequency and severity, disproportionately affecting those impacted by financial and health disparities. Future research must include the implications of population health in the context of GeoHealth as a result of the most recent drought and the receding water levels of the Salton Sea.

Shrinking lakes, air pollution, and human health: Evidence from California's Salton Sea

Due to increased water withdrawals and ongoing climate change, many inland lakes around the world are shrinking and dry lake beds can be significant sources of particulate matter air pollution. Using a natural experiment provided by the shrinking Salton Sea in California, this paper shows that each one-foot drop in lake elevation is associated with a 0.28 μg/m³ (2.6%) increase in PM2.5 concentrations. IV model results then show that Salton Sea-induced changes in PM2.5 over 1998-2014 led to increases in respiratory mortality of 1.4/yr.-15.6/yr. in the counties surrounding the lake, generating $13.2-$147.3 million in annual health costs.

Assessment of Respiratory Health Symptoms and Asthma in Children near a Drying Saline Lake

Residents of the Imperial Valley, a rural, agricultural border region in California, have raised concerns over high rates of pediatric asthma symptoms. There is an urgent need to understand the influences and predictors of children's respiratory health in Imperial Valley. We assessed the impacts of sociodemographic, lifestyle, and household factors on children's respiratory health and asthma prevalence by administering a survey to parents of elementary school children (n = 357) in northern Imperial Valley. We observed an overall asthma prevalence of 22.4% and respiratory symptoms and allergies were widely reported, including wheezing (35.3%), allergies (36.1%), bronchitic symptoms (28.6%), and dry cough (33.3%). Asthmatics were significantly more likely to report respiratory symptoms, but high rates of wheezing, allergies, and dry cough were observed among nonasthmatics, suggesting the possibility for underdiagnosis of respiratory impairment in our school-age population. Having an asthmatic mother and exposure to environmental tobacco smoke were also associated with greater odds of asthma. Our findings provide evidence to support community concerns about children's respiratory health, while also suggesting that household and demographic characteristics have limited explanatory power for assessing asthma in this population. This work provides critical baseline data with which to evaluate local environmental factors and their influence on asthma and respiratory symptoms.