ENVIRONMENT

How Wildfire Smoke in San Francisco Made People Sick: A Data Detective Story

San Francisco County, California, USATue Jul 15 2025

The Challenge

Wildfires are a significant threat, causing widespread destruction and poor air quality. In 2018, a major wildfire in California sent smoke to San Francisco. Scientists sought to understand the health impacts of this smoke, but conducting direct experiments was unethical and unsafe.

The Solution

Researchers employed a clever method to study the effects:

  • Data Analysis: They examined hospital records before and after the smoke arrived.
  • Time Machine Analogy: This approach is akin to using a time machine to predict what would have happened without the smoke.
  • Computer Programs: Special algorithms were used to estimate hospital visits under clean air conditions.
  • Comparison: The estimates were compared to actual hospital visits during the smoke event.

Key Findings

  • Best Performing Model: The Prophet-XGBoost program provided the most accurate predictions.
  • Estimated Impact: The smoke likely caused approximately 92 additional hospital visits for breathing problems.
  • Range of Uncertainty: The actual number could range from 24 to 125.

Broader Applications

This method isn't limited to wildfires. It can be applied to study the health effects of other environmental events, such as:

  • Severe weather conditions
  • Major environmental incidents

Limitations

While this approach is valuable, it has its limitations:

  • Not Perfect: It's akin to a detective solving a mystery with incomplete clues.
  • Careful Use: The method should be used judiciously and supplemented with additional research.

questions

    What are the limitations of using Interrupted Time Series (ITS) analysis in assessing the health effects of extreme weather events?
    How reliable are the data sources used to estimate the health impacts of the wildfire smoke?
    Is it possible that the wildfire smoke was just a clever marketing ploy by the hospital industry?

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