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Josh Apte

@joshapte.bsky.social

205 followers 153 following 13 posts

Professor of Environmental Engineering + Environmental Health Sciences, UC Berkeley. Research: air pollution, health, climate, EJ.

Posts Replies Media

Josh Apte @joshapte.bsky.social · 27/04/2025

I took advantage of the spring weather to sneak in a little hike in the Viennese Alps this morning before the start of #EGU25. Awesome to see this old smokestack being repurposed for solar energy. A nice metaphor for the change we need!

An old brick building with a smokestack. The smokestack is now covered with PV panels.

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Josh Apte @joshapte.bsky.social · 16/04/2025

Postscript: the 40-year old diesel locomotives are now retired, but they are not at the end of the line quite yet. Many will be exported to Peru soon to start a new commuter service.

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Josh Apte @joshapte.bsky.social · 16/04/2025

Bottom line: electrification can bring huge air quality benefits to rail systems and the communities they run through. We have dozens of other commuter rail systems that still use mostly older diesel locomotives. We should electrify them ASAP.

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Josh Apte @joshapte.bsky.social · 16/04/2025

The reduction in black carbon at the SF station was so large that we saw the same drop in BC as what California cities achieved from *30 years* of clean air regulation!

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Josh Apte @joshapte.bsky.social · 16/04/2025

Over the 6 weeks of the electric transition, there was a clear correlation between days with fewer diesel locomotives idling and days with better air quality near the SF station. Once the diesel locomotives were retired, we found almost no detectable increment in diesel smoke near the station.

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Josh Apte @joshapte.bsky.social · 16/04/2025

So, we equipped the SF Caltrain station with instrumentation to detect how much diesel smoke was coming from the locomotives.

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Josh Apte @joshapte.bsky.social · 16/04/2025

Before electrification, the SF Caltrain station was noisy and smoky at nearly any hour of day. Why? An arcane safety regulation requires that locomotives have a careful safety inspection if they are shut down for too long. So, they usually were just left running.

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Josh Apte @joshapte.bsky.social · 16/04/2025

On diesel trains, smoke would blow straight into the passenger cars. Concentrations of black carbon were nearly as high as what I have measured in New Delhi traffic. Electric trains were almost 90% cleaner on board! This brings a meaningful reduction in cancer risk for staff & regular riders.

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Josh Apte @joshapte.bsky.social · 16/04/2025

We tracked concentrations of black carbon (BC) on-board dozens of diesel and electric trains. BC is an excellent marker for diesel particulate matter, which is the #1 airborne carcinogen in California.

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Josh Apte @joshapte.bsky.social · 16/04/2025

Caltrain used to operate a fleet of 40-year old diesel-powered trains. Over 6 weeks last summer, these locomotives were swapped for sleek new electric trains. The rapid transition made it easy for us to quantify the big air quality benefits.

Diesel and electric Caltrain, side-by-side.

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