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I recall this claim being published in a newspaper a while back but time has buried it in the Interwebs, though it does come up from time to time as e.g.

Driving a jet ski for one hour will produce the equivalent amount of pollution as driving a new car 100,000 km.

My recollection was that the comparison was to a Honda Civic from the early 2000's, but I suppose the claim could be validated by a comparison to any small, new model of car.

Is there any merit to this claim?


EDIT The original claim appears to come from the California Air Resources Board, per Environmental Science: Problems, Connections and Solutions By G. Miller, Scott Spoolman, p. 357. It appears to be widely cited as such on the Internet, though I have yet to find the source material.

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Driving a jet ski for one hour will produce the equivalent amount of pollution as driving a new car 100,000 km.

This claim seems to be INCORRECT.

First, the claim appears to be credited to Stienstra (1998):

The state Air Resources Board is also considering taking statewide action against personal watercraft, after a staff report said that two hours of exhaust emissions from a Jet Ski is equivalent to the emissions created by driving a 1998 automobile 130,000 miles.

In addition, the amount of hydrocarbons and nitrogen oxides released in the air by Jet Skis and outboard motors totaled 312 tons per day.

"Jet Skis produce nine times the hydrocarbon emissions as outboard motors," said Russell Long of the Bluewater Network in San Francisco, which has led the national opposition to personal watercraft.

But, after digging deeper, I was able to find the staff report:

Here is an extract from the report published by Air Resources Board has been reviewed by the staff of the California Air Resources Board and approved for publication:

Applicability. The proposed exhaust emission standards are applicable to outboard marine and personal watercraft engines, including jet boats.

Emissions Impact. Emissions of hydrocarbons (HC) and oxides of nitrogen (NOx) from outboard and personal watercraft in 1997 totaled 312 tons per day. This compares to 1,374 tons per day statewide for passenger cars. While reductions from gasoline SI marine engines are not included in California’s SIP as a planned measure for meeting attainment goals, the impact of outboard and personal watercraft engines on the state’s total emissions inventory makes control of this category of emissions necessary. Table 1 lists the relative contribution of outboard and personal watercraft exhaust emissions in California in tons per day. As a comparison to other sources, the exhaust emissions from two hours of personal watercraft operation is equivalent to the emissions from a 1998 passenger car operated over 100,000 miles.

This regulation is also driven in part by concerns over discharge of unburned fuel into lakes, reservoirs and waterways. According to studies cited in the U.S. EPA gasoline SI marine engine rulemaking, conventional two-stroke engines discharge 25 to 30 percent of fuel unburned into the water. Recent attention focused on detection of methyl-tertiary-butyl-ether (MTBE) in drinking water supplies has caused a number of water quality agencies to consider restriction of two-stroke watercraft on particular waterways. Other gasoline constituents emitted into the water, including carcinogenic benzene and toluene, have also been of significant concern.

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If you look closer, it seems that Stienstra (1998) misinterpreted and/or misunderstood the english behind the report. With the help of our friends from english.stackexchange.com, it can be concluded that:

The official report by Air Resources Board official said that:

As a comparison to other sources, the exhaust emissions from two hours of personal watercraft operation is equivalent to the emissions from a 1998 passenger car operated over 100,000 miles.

But it was paraphrased incorrectly by Stienstra (1998):

After a staff report said that two hours of exhaust emissions from a Jet Ski is equivalent to the emissions created by driving a 1998 automobile 130,000 miles.

The correct interpretation (suggested by @Senex) is:

All the watercrafts operating in California together produce in 2 hours the same pollution as one car driven 100,000 km

Explanation:

Prior to what was quoted from the scientific report:

Emissions of hydrocarbons (HC) and oxides of nitrogen (NOx) from outboard and personal watercraft in 1997 totaled 312 tons per day.

That number of tons per day equals 26 tons per 2 hours, which is close to the approximately 26 tons of CO₂E an average car emits while traveling 100,000km.

This figure arises as follows: From the EPA's refs.html, section Miles driven by the average passenger vehicle per year, average car emissions are 4.20 x 10⁻⁴ metric tons CO₂E per mile. For 100,000 miles, that's a total of 42 metric tons CO₂E (CO₂ equivalent, which encompasses “carbon dioxide, methane, and nitrous oxide, all expressed as carbon dioxide equivalents”). Emissions per 100,000 km is about 5/8 as much, or about 26 tons. (More precisely, 26.098 tons = 42 tons * 100000 miles/160934 km, but even two significant digits is too many.)


Stienstra, T. (1998, Jul 08). U.S. park service seeks ban on jet skis 950 square miles of bay area waters would be affected. San Francisco Examiner. Retrieved from http://search.proquest.com/docview/270486538?accountid=8555

The claim:
2 hours of Jet Ski driving are equivalent to 130,000 miles.
2 hours of Jet Ski driving are equivalent 209,215 kilometers.
1 hour of Jet Ski driving is equivalent to 104,607.5 kilometers.
1 hour of Jet Ski driving almost equivalent to 100,000 kilometers.

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    That's repeating the claim, or a source of the claim. Does it tell us whether the claim is true? Or does it only say that the claim was contained in a staff report? – ChrisW Aug 29 '14 at 23:50
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    Thanks for finding the text of the claim! It doesn't say where it gets its numbers from but, oh well: I can assume they come from somewhere plausible. When it says, "the exhaust emissions from two hours of personal watercraft operation is equivalent to the emissions from a 1998 passenger car operated over 100,000 miles", I wonder what kind of emissions is it talking about? I guess it's either "HC+NOx" as shown in Table 2, or, "HC+NOx" and "CO" as well (but ignoring CO2) as show in Table 1. My last question is, what were the corresponding exhaust emissions numbers from a 1998 passenger car? – ChrisW Aug 30 '14 at 7:23
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    @georgechalhoub Another more likely possibility just occurred to me: that the report means that all the watercraft operating in California together produce in 2 hours the same pollution as one car driven 100,000 km. Then Stienstra's mistake could be to interpret that as meaning that one jetski operated for 2 hours produces that amount of pollution. I think this is a better fit both with the logic of the situation and the language of the report. (I also posted this comment on your english.SE question.) – Senex Sep 4 '14 at 14:31
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    @georgechalhoub Glad to help in a small way. Thank you for the excellent answer -- it summarizes and clarifies everything very well. – Senex Sep 4 '14 at 21:06
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    Great work. The one improvement that just add a little clarity is to have the per-hour pollution of a jet-ski and compare it to the same for a 1998 car. – Brian M. Hunt Sep 4 '14 at 21:32

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