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Estimating the Exposure-Response Relationship between Fine Mineral Dust Concentration and Coccidioidomycosis
Amanda K Weaver1, Nicole Keeney1, Jennifer R Head1
1Division of Environmental Health Sciences, School of Public Health, University of California Berkeley, Berkeley, California, USA.
Background:
Coccidioidomycosis, caused by inhalation of Coccidioides spp. spores, is an emerging infectious disease that is increasing in incidence throughout the southwestern US. The pathogen is soil-dwelling, and spore dispersal and human exposure are thought to co-occur with airborne mineral dust exposures, yet fundamental exposure-response relationships have not been conclusively estimated.
Objectives:
We estimated associations between fine mineral dust concentration and coccidioidomycosis incidence in California from 2000 to 2017 at the census tract level, spatiotemporal heterogeneity in exposure-response, and effect modification by antecedent climate conditions.
Methods:
We acquired monthly census tract-level coccidioidomycosis incidence data and modeled fine mineral dust concentrations from 2000 to 2017. We fitted zero-inflated distributed-lag nonlinear models to estimate overall exposure-lag-response relationships and identified factors contributing to heterogeneity in exposure-responses. Using a random-effects meta-analysis approach, we estimated county-specific and pooled exposure-responses for cumulative exposures.
Results:
We found a positive exposure-response relationship between cumulative fine mineral dust exposure in the 1-3 months before estimated disease onset and coccidioidomycosis incidence across the study region [incidence rate ratio (IRR) for an increase from 0.1 to ; 95% CI: 1.46, 1.74]. Positive, supralinear associations were observed between incidence and modeled fine mineral dust exposures 1 [ (95% CI: 1.10, 1.17)], 2 [ (95% CI: 1.09, 1.20)] and 3 [ (95% CI: 1.04, 1.12)] months before estimated disease onset, with the highest exposures being particularly associated. The cumulative exposure-response relationship varied significantly by county [lowest IRR, western Tulare: 1.05 (95% CI: 0.54, 2.07); highest IRR, San Luis Obispo: 3.01 (95% CI: 2.05, 4.42)]. Season of exposure and prior wet winter were modest effect modifiers.
Discussion:
Lagged exposures to fine mineral dust were strongly associated with coccidioidomycosis incidence in the endemic regions of California from 2000 to 2017. https://doi.org/10.1289/EHP13875.
Insights
Fine mineral dust exposure is linked to increased coccidioidomycosis incidence in California. Higher dust levels, particularly 1-3 months prior, significantly raise the risk of this emerging infectious disease.
Area of Science:
- Environmental epidemiology
- Infectious disease ecology
Background:
- Coccidioidomycosis is an emerging infectious disease in the southwestern US.
- The soil-dwelling fungus Coccidioides spp. causes coccidioidomycosis via spore inhalation.
- Spore dispersal and human exposure are linked to airborne mineral dust.
Purpose of the Study:
- To estimate the relationship between fine mineral dust concentration and coccidioidomycosis incidence in California.
- To investigate spatiotemporal variations in exposure-response.
- To assess the modifying effects of antecedent climate conditions.
Main Methods:
- Utilized census tract-level coccidioidomycosis incidence data (2000-2017).
- Modeled fine mineral dust concentrations and fitted zero-inflated distributed-lag nonlinear models.
- Employed random-effects meta-analysis for county-specific and pooled exposure-responses.
Main Results:
- A positive exposure-response relationship was found between cumulative fine mineral dust exposure (1-3 months prior) and coccidioidomycosis incidence.
- Supralinear associations were observed for dust exposures 1, 2, and 3 months before disease onset.
- Significant county-level variation in exposure-response was noted, with some counties showing substantially higher risks.
Conclusions:
- Lagged exposure to fine mineral dust is strongly associated with coccidioidomycosis incidence in endemic California regions.
- Understanding these exposure-response relationships is crucial for public health interventions.
- Climate conditions may modestly modify the risk of coccidioidomycosis following dust exposure.
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