How many people did VW’s NOx defeat device kill? Over the weekend I did a rough estimate and figured that over the past six years VW’s excess NOx emissions probably killed about a dozen people in Southern California. Since then I’ve slightly revised my spreadsheet to account for an error, which increases my estimate to about 17 people killed. My figuring was based on:
- 50,000 cars sold in Southern California between 2009-2014
- 3,800 excess tons of NOx over six years
- 0.0044 deaths per ton of NOx
VW sold 500,000 altered cars in the US and 11 million cars worldwide, so this extrapolates to about 170 deaths in the United States and about 3,700 deaths worldwide.
The number of cars sold is a solid figure, and as near as I can tell the estimate of 0.0044 deaths per ton of NOx is reasonable (this paper estimates a range of .0019 to .0095). But others have come up with higher mortality estimates than mine based on a much higher estimate of excess NOx emissions. So here are my calculations:
- The ICCT, which discovered the violation, says VW cars “exceeded the US-EPA Tier2-Bin5 (at full useful life) standard” by 10-35 times depending on model.
- The Tier2-Bin5 standard is 0.07 grams per mile.
- If VW cars averaged 30x the standard, that’s 2.1 grams per mile.
- Based on (a) increasing sales year over year and (b) the fact that older cars have driven more miles, I figure that the affected cars have been driven about 1.6 billion total miles over six years.
- That comes to 3.5 billion grams of NOx, or about 3,800 tons.
This extrapolates to 38,000 tons for the United States. That’s over six years. But using the same excess emission rate of 30x that I did, the Guardian figures about 31,000 tons per year. That’s five times my estimate.
My full spreadsheet is here. I invite comments.