Figure 1:

Title: AQI Scores for the Top 5 Cities in California
Subtitle: A dashboard for PHW251B students
Data source: top5_cities.rds

Background:
This dataset presents Air Quality Index (AQI) scores for five major cities in California: Bakersfield, Bishop, Fresno, Los Angeles, and Riverside. The data were extracted from top5_cities.rds and reflect AQI measurements over a defined time period, capturing both typical pollution levels and extreme outlier events. The study population includes urban centers with diverse geographic and industrial profiles, offering a comparative lens on regional air quality. The research question guiding this dashboard is: How does air pollution vary across California’s top cities, and which locations exhibit the most severe or volatile AQI patterns? This analysis is important for public health students and policymakers because it highlights environmental disparities, identifies pollution hotspots, and supports targeted interventions to improve air quality and reduce exposure-related health risks.

Results:
The boxplot visualization reveals substantial variation in AQI scores across the top five Californian cities, underscoring both chronic and episodic pollution risks. Bishop stands out with extreme outliers reaching AQI values near 1000, suggesting rare but severe pollution events that may be tied to wildfires, industrial activity, or geographic vulnerability. In contrast, Los Angeles and Riverside exhibit tighter distributions with elevated median AQI values, indicating more consistent exposure to moderate-to-high pollution levels. Bakersfield and Fresno show wider interquartile ranges, reflecting fluctuating air quality likely influenced by agricultural emissions and seasonal factors. These patterns suggest that while urban centers like Los Angeles face persistent air quality challenges, smaller cities such as Bishop may experience acute environmental stressors that are less predictable but potentially more hazardous. The take-home message is that AQI variability across regions demands tailored public health responses: chronic exposure mitigation in urban hubs, and emergency preparedness in areas prone to extreme events.

Figure 2:

Title: Time trends of AQI values for the top 5 cities in California
Subtitle: A dashboard for PHW251B students
Data source: top5_cities.rds

Background:
This dashboard presents annual Air Quality Index (AQI) trends from 1980 to 2020 for five California cities—Bakersfield, Bishop, Fresno, Los Angeles, and Riverside—using population-weighted data to reflect exposure-adjusted averages. The dataset, sourced from top5_cities.rds, captures long-term shifts in urban air quality, highlighting both progress and persistent disparities across regions. Our goal is to help viewers assess how environmental policies have shaped public health outcomes over time, identify cities with ongoing pollution challenges, and use this evidence to inform advocacy, planning, and intervention. By visualizing these patterns, we aim to support data-driven decisions that promote cleaner air and healthier communities.

Results:
The results of this analysis show that annual AQI values across Bakersfield, Bishop, Fresno, Los Angeles, and Riverside declined steadily from 1980 to 2020, reflecting significant improvements in air quality over time. Bishop consistently maintained the lowest AQI levels, while Los Angeles and Riverside, once among the most polluted, demonstrated sharp reductions, suggesting the impact of regulatory measures and cleaner technologies. Bakersfield and Fresno also improved, though their AQI values remain relatively higher compared to Bishop. Notably, there was a stark decrease in AQI values in 2020, coinciding with the COVID‑19 pandemic, when widespread lockdowns and reduced economic activity temporarily lowered emissions. The take‑home message is that California’s urban centers have made substantial progress in reducing air pollution, but disparities persist, underscoring the need for continued monitoring and targeted interventions to ensure all communities benefit equally from cleaner air