According to a new study published in Geophysical Research Letters, cows may be as much to blame for L.A.’s notorious smog problem as cars.

Researchers from the University of Colorado teamed up with the National Oceanic and Atmospheric Association to study the composition of and contributors to L.A.’s smog. The study team found that a large portion of the city’s smog is comprised of ammonium nitrate. Ammonia reacts with nitrogen oxides (Nox) in the atmosphere to form smog.

It comes as no surprise that Los Angeles’ 9.9 million automobiles generate an estimated 62 metric tons of ammonia each day. But manure from the city’s 298,000 dairy cows  generates somewhere between 33 and 176 metric tons of ammonia per day!

The California Dairy Industry says the study over-estimated the number of cows in the L.A. basin (although USDA data supports the study’s estimate), and questions their calculations. Still, that’s a lot of cows, a lot of manure, and a lot of ammonia. And it’s certainly not helping the city’s smog problem.

All this to produce milk, cheese and other dairy products that may cause cancer, are NOT beneficial for bone health, and are not even among the best sources of calcium.

Image Credit: BugMan50/Flickr