The Price of Liberty is Eternal Vigilance
How much air pollution do cruise ships really create?
Not nearly as much as cruise ship opponents allege!Warwick Jones
Facts never seem to get in the way of cruise ships opponents. The letter to the Post and Courier on July 23 by Ms. Carrie Agnew of Charleston Communities for Cruise Control suggests that all the citizens on the peninsula should be dropping with respiratory diseases. We arenít. But if we were, the cause would lie more with vehicular traffic rather than cruise ship emissions. Here are some facts!
Cruise ship visits average two a week and the ships are in port for about 9 hours during each visit. This amounts to 18 hours of the 164 hours in a week i.e. about 11% of the available time.
The cruise ship terminal is on the most easterly edge of the peninsula. For winds to spread emissions over the peninsula, they would need to blow in a direction between NNW to SSW. Checking the hourly wind pattern when the ships are generally docked, from 7.30 a.m. to 4.30 p.m. the wind blows within this defined direction about 25% of the time. This percentage has been estimated from daily data over the last 4 years, available on Weatherunderground.com. Most of the time it seems, emissions from cruise ships are blown up or over the Cooper River or out to sea.
So the probability of emissions being blown across the Peninsula in any hour is 11% times 25%, which amounts to less than 3%. If the measurement included only winds with a pure Westerly direction, taking them over Ansonborough where Ms. Agnew complains about soot and particulates, the probability would be less than 2%, I calculate.
These donít seem life-threatening exposures. And they certainly donít seem life threatening considering that most of the engines of cruise ships are turned off in port. Those or that running is at a level a fraction of full throttle and sufficient only to generate electricity for the ship.