Wikipedia:Reference desk/Archives/Science/2015 September 22

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

September 22

How many people have died due to Volkswagen's defeat devices?

Based on [1][2], I'd like to come up with a figure for how many people have been killed by the software that allowed Volkswagens to sense when they are being tested for emissions and producing lower levels only at that time. This involves:

A) What are the total number of air pollution deaths caused by nitrogen oxides? (as I understand it, some are caused by particulates, ozone, etc. - so I see figures for overall mortality like 55,000 in the U.S. and 30,000 in Britain (which don't seem very reconcilable to start) but so far I've only seen partial answers for NOx e.g. [3].

B) What portion of the total nitrogen oxide production can be attributed to the cheating software? (I am seeing figures like 10 times too much for each car, but I don't know how much is emitted per car and how much that is for X million cars, versus the total emission) Note that the calculation has to be bottom-up rather than assumed from a market share where the others are all honest, because there are already reports of other brands possibly doing the same thing.

Of course, if someone can simply cite a direct analysis, that would be even better! Wnt (talk) 13:18, 22 September 2015 (UTC)

I tried estimating this earlier. I got that the 480,000 US cars emitted roughly 17 kilotons more NOx than allowed by regulations (assuming emissions 40-fold above regulations and US average miles travelled), which is a drop in the bucket given that US annual emissions are 11100 kilotons (EPA for 2013). For the US, mortality is dominated by particulate matter (90%) and most of the remainder is due to ozone. NOx itself is probably a very small factor in mortality, though NOx does react to promote ozone and particulate formation, and it could be difficult to figure out that indirect effect. Though, given that it is only a 0.1% increase in total emissions and it is only a minor player in mortality, the net effect is likely much less than 0.1% increase in air pollution mortality. The only likely exception to this is if these cars happen to be geographically concentrated in a way that is not proportional to other NOx sources, and for that I don't really know. Dragons flight (talk) 13:56, 22 September 2015 (UTC)

Correction FWIW, the cars mask the emissions with urea when being tested; they do not suddenly produce lower emissions.DrChrissy ^(talk) 13:24, 22 September 2015 (UTC)

Urea reacts with NOx emissions to convert it to harmless substances. See selective catalytic reduction. That's real reduction in tail pipe emissions, which is what we ultimately care about, and not just masking. Of course it does no good if the car turns off the urea system, as VW was apparently doing. Dragons flight (talk) 13:56, 22 September 2015 (UTC)

Ah, I see. Thanks for correcting my correction.DrChrissy ^(talk) 14:59, 22 September 2015 (UTC)

It's a tough calculation. It's clear that the very large numbers for the emissions are only happening in certain driving patterns - so the numbers being kicked around are likely the peak emission rate. The average (which is what we really care about) is probably much lower. But I don't think sufficient study has been done on this to really know the full effects of this deception over a range of different cars and a range of different driving patterns.

There an argument that diesel engined cars are more fuel-efficient than gasoline engines - which results in lower overall emissions - you might argue that if Volkswagen had not done this, more people would have bought gasoline-powered cars and that would have made things worse overall...or you might argue that more people would have bought hybrids had there not been fuel-efficient diesels and that would have made things better overall. That's an almost impossible question to answer.

More complication comes from the fact that this trick was done to improve fuel economy...which it undoubtedly did - and with huge success. So what we have here is a car that produces less CO2 than it would have done if it followed the EPA rules and burned more fuel - but simultaneously produces more NOx than it should have done. So your calculation of lives lost to excess NOx should also include lives saved due to reduction in CO2, sulfur and other pollutants typically generated by diesel engines. That's a much tougher calculation because the vast majority of deaths attributable to CO2 emissions probably won't happen for a few more decades as the effects of global climate change kick in - we simply don't know how many will die as a result.

Suffice to say that whatever calculations you might come up with from total deaths due to NOx (etc) divided by the percentage of excess NOx caused by Volkswagen - you will miss those two important factors, and that renders your results meaningless.

Personally, I don't condone what Volkswagen did - but don't think it's at all clear that Volkswagen will have caused any deaths at all - especially if you look sufficient years into the future so that the effects of CO2 emissions can be included into the calculations. I've always believed that the EPA restrictions on diesel engines (and especially on diesel FUEL) are ill-conceived because they principally relate to large trucks - and their emissions patterns are totally different. The world would undoubtedly be better if more people could be persuaded to drive small diesel engined cars. Those cars are extremely popular in Europe - but much less so in the USA because of inappropriate EPA restrictions for small diesel engines.

SteveBaker (talk) 13:43, 22 September 2015 (UTC)

Are you sure the trick was done primarily to improve fuel economy? When I research the slightly related question on RDC, I saw various other suggestions like it being done to increase power (which may or may not improve fuel economy) or simply that it was done to reduce the need for maintenance. The sources I provided on RDC discusses this a bit. Nil Einne (talk) 14:44, 22 September 2015 (UTC)

From what I've been reading, the trick definitely improves both power and fuel economy. Whether it was intended to do just one of those things - and the other was just a fortuitous side-effect - is anyone's guess. In retrospect, people should perhaps have wondered how the car was getting so much better MPG in practical day-to-day driving than they were getting when the EPA measured their MPG on the test track. We don't know whether Volkswagen management made their software guys do this and then swore them to secrecy - or whether the software team - or maybe just one programmer - did it without telling anyone. We don't know whether that software was written in-house or by some outside contractor (I happen to know that the engine management software for the MINI Cooper wasn't written by either MINI or their parent BMW company - so it could easily have been out-sourced). Assigning either motive or blame is difficult at this point. What's clear is that TDI Diesel owners are going to be mightily pissed when they have to have their software replaced and suddenly get less acceleration and worse gas mileage out of cars they've owned for a year or three! If they refuse to go for the recall in sufficient numbers then the EPA are going to have a hard time knowing how to handle emissions inspections in the future. SteveBaker (talk) 19:40, 22 September 2015 (UTC)

@Wnt:, @SteveBaker:, @Dragons flight: don't know if you've heard of this but I was reading [4] which mentioned something about an AP analysis. Looking, I came across two different recent analysis, the AP one [5] and a seperate NY one [6] (actually both appear to include more than one). Also found some briefer older estimates [7] [8].

I didn't look that well yet but the estimates seem to be in the tens to 100+ deaths in the US in the past seven years. These are ball park estimates (they don't seem to have considered things likes power and efficiency that SB and others mentioned), but guess may be useful if you're still interested. Most of what I've read suggest that the numbers would be higher in Europe given there are more cars with affected VW diesel engines there. (I suspect much of the developing world is an interesting thing given that standards tend to be laxer. And this sort of cheating may have made VW a more attractive option compared to cheaper cars which may not comply with stricter regulations elsewhere. Or allowed VW to sell their products in those markets rather than cheaper alternatives with perhaps even worse emissions. And emissions are only one aspect, the alternatives may also have differing, probably worse safety standards.)

Interestingly, so far all I can find so far about these estimates from Volkswagen seems to be that the EPA has said their cars aren't safety hazards and "General allegations regarding links between NOX emissions from these affected vehicles and specific health effects are unverified. We have received no confirmed reports that the emissions from such vehicles caused any actual health problem". (mentioned in AP source and [9]) which seems to be basically saying that they can't find any flaw in the estimates, but you won't be able to link our cars with any specific deaths or health effects in specific people.

Nil Einne (talk) 11:58, 4 October 2015 (UTC)

@Nil Einne: THANKS for reminding me! I have updated Volkswagen emissions violations accordingly. Wnt (talk) 13:05, 4 October 2015 (UTC)

Concentration of odorant in natural gas

Natural gas§Safety§§Use says: "In order to assist in detecting leaks, a minute amount of odorant is added to the otherwise colorless and almost odorless gas used by consumers." How much is "a minute amount"? In other words, what is the typical concentration of odorant in the final mix piped to consumers?

Chapter IV Leak Detection^PDF of the Texas Railroad Commission's simplified description of federal pipeline safety regulations says: "Gas is intentionally odorized so that the average person can perceive it at a concentration well below the explosive range. That odorant concentration is generally between 0.5 to 1.0 percent by volume or as local applicable codes dictate." which is much less "minute" that I would have expected, and I wonder if whoever worked up the simplified description was confused by a requirement that the odor be detectable when a leak yields a natural gas concentration of 0.5 to 1.0 percent by volume. (See 49 CFR 192.625 - Odorization of gas (a): "A combustible gas in a distribution line must contain a natural odorant or be odorized so that at a concentration in air of one-fifth of the lower explosive limit, the gas is readily detectable by a person with a normal sense of smell.") -- ToE 13:24, 22 September 2015 (UTC)

Methyl mercaptan, the odorant usually used, has an odor threshold of 0.002 ppm (parts per million) or 2 ppb (parts per billio (see here That means that 2 mL of methyl mercaptan distributed in a volume of 1,000,000 liters is detectable. If gas was doped with 1 percent methyl mercaptan, that's one part per hundred, so the gas leak would be detectable at 200 ppb, or 0.2 ppm, or 2 mL of gas per 10,000 liters. --Jayron32 14:12, 22 September 2015 (UTC)

Smelly stuff indeed. The last time a factory in France had a leak, Brits 200 miles away called the police complaining of noxious odour. Ssscienccce (talk) 14:36, 22 September 2015 (UTC)

The kind used in America, at least, is strong but a lot less noxious than cigarette smoke, for example. — Preceding unsigned comment added by Baseball Bugs (talk • contribs) 05:01, 23 September 2015 (UTC)

North and south pole

Why is the North Magnetic Pole a south pole and vice versa? GeoffreyT2000 (talk) 14:02, 22 September 2015 (UTC)

If by "why" you mean why the names are opposite their magnetic nature, see Magnet#Pole_naming conventions. If you mean why the poles at these locations actually have the magnetic nature they do, Earth's magnetic field talks about the origin of the effect and that it does change over time. DMacks (talk) 14:12, 22 September 2015 (UTC)

André-Marie Ampère, inspired by Oersted's discovery published 1820 that electric current visibly affected magnet needles, established rigourously in 1822 that magnetism is produced by "electricity in motion". In his words: if an observer has a current flowing from his feet to his head then a needle placed in front of him would have its north-seeking pole deflected to his left. Today we express this in Ampère's right hand screw rule and consider that all magnetism, even that of permanent magnets, is due to circulating currents, see Magnetization. Such currents produce a directed magnetic field (an isolated north or south pole cannot be realized). The Earth itself is a big electromagnet where the so-called North magnetic pole is by electrodynamics a south pole - the apparent paradox arises because of the convention to identify the north-seeking pole of every magnet as "North" regardless of whether it might actually be useful as a compass needle. These days we celebrate Monsieur Ampère in our unit of current which he first defined together with electric tension (voltage) some years before Ohm's law was published 1826-27. 84.209.89.214 (talk) 18:22, 22 September 2015 (UTC)

1) The direction of "north" developed, at least in the Indo-European languages, from the name given to where your left arm points when you hold out your arms to the side facing the dawn. The word north comes from the PIE root *ner-.

2) It was eventually discovered that the earth rotates about an axis, and we now call the points where the axis intersects the surface the North and South Poles. It was discovered well before Columbus that a permanently magnetized free-floating bar would tend to align north-south. Mariners realized that if they marked the ends of the bar, they could use it to identify north versus the south, even during cloudy weather or under strange stars.

3) Eventually it was realized that the north and south magnetic poles did not exactly correspond to the axial poles. It was further realized how magnetism works, and the "north" end of a magnet or magnetic field is attracted to the south end of another magnet or magnetic field.

4)In the 1800's it was finally fully realized that the earth was generating a magnetic field with its poles close to the axial poles, and that hence the earth itself is analogous to a giant magnetic bar with its south pole near the north axial pole, and vice versa.

μηδείς (talk) 17:35, 24 September 2015 (UTC)

Ahem... William Gilbert. Alansplodge (talk) 18:44, 25 September 2015 (UTC)

Bless you. "His primary scientific work—much inspired by earlier works of Robert Norman[5][6]—was De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure (On the Magnet and Magnetic Bodies, and on the Great Magnet the Earth) published in 1600. In this work, he describes many of his experiments with his model Earth called the terrella. From these experiments, he concluded that the Earth was itself magnetic and that this was the reason compasses point north (previously, some believed that it was the pole star (Polaris) or a large magnetic island on the north pole that attracted the compass). He was the first to argue, correctly, that the centre of the Earth was iron, and he considered an important and related property of magnets was that they can be cut, each forming a new magnet with north and south poles." Sounds like Gilbert thought the earth was a permanent magnet, and he denied a connection between electricity and magnetism. See Electromagnetism#History_of_the_theory for why I said, "In the 1800's it was finally fully realized that the earth was generating a magnetic field." μηδείς (talk) 01:10, 26 September 2015 (UTC)

what exactly is the sense of this kind of a Tractor Road-rail vehicle?

Like this ? This kind of road-rail vehicle is so popular you can buy it in H0 scale for your model train... I don´t understand what does a Tractor have to do on the rails... It would use more fuel than a simple Train.. --Hijodetenerife (talk) 18:40, 22 September 2015 (UTC)

It may be used as a rail car mover, which is cheaper and easier than a switcher locomotive. It may be used for construction.

The thing about rail transport is that there are tons of specialized equipment; and all this neat special-purpose gear exists because trains weigh tons. If you want to move a rail car thirty feet across the yard, you can hardly get out and push! You either need a full-blown locomotive - which means spending the time and money to get a locomotive, or else you need to use specialized gear. If you need to repair a piece of equipment out on the line, the only way to get there might be along the railway, so a hybrid road/rail vehicle might be the best way to get there.

The vehicle in the photograph linked above is a Fortschritt (East German) rail tractor. It has an article in the German Wikipedia, Zugtraktor ZT 300. "Einige Traktoren wurden zu Zweiwege-Traktoren umgerüstet und als Rangiergeräte vor allem in DDR-Kleinbetrieben mit Bahnanschluss eingesetzt. Neben den erforderlichen Signaleinrichtungen (Spitzen- und Zugschlusssignal) waren diese Traktoren mit hydraulisch absenkbaren Spurkränzen ausgestattet." (That is, they were modified for use in East Germany for rail yard switching at smaller depots by adding the rail wheels, suspension, and legally-required rail lighting beacons).

Nimur (talk) 19:42, 22 September 2015 (UTC)

But they need more fuel and a regular tractor is driving outside the streets for plants.. I don´t know why a tractor should be abused to drive freight car´s or wagons.. There are yet other Road-rail vehicle which can do this. --Hijodetenerife (talk) 04:01, 23 September 2015 (UTC)

I would translate "Kleinbetrieben mit Bahnanschluss" as "small businesses connected to the railway" rather than "smaller depots" (although it is a bit ambiguous), which helps answer your question. Yes, there are more efficient ways to move wagons... but East Germany was not a terrifically rich country, and its industries struggled to match the advances that West Germany made during the Wirtschaftswunder. You could buy your factory a dedicated freight tractor and a dedicated shunter locomotive, but you would need to pay for, maintain and train your staff on two totally different specialized vehicles. You can get almost the same benefit much cheaper by just sticking railway wheels on a mass-produced agricultural tractor. Smurrayinchester 10:59, 23 September 2015 (UTC)

My guess: Most tractor types can be fitted with a variety of implements and have levers or switches to raise and lower such attachments. So adding the flanged steel wheels only requires a rigid or hinged attachment, the mechanism to raise and lower them is already in place. Why buy an expensive rail car mover when you can adapt an old tractor to do the same job. Also, rail tracks don't usually have roads next to them, a tractor would have excellent off-rail performance on rough terrain, loose soil, etc..

The fuel efficiency is not a factor, they are only used to move railroad cars over limited distances. The advantage is that it can move off the track, so you don't need a network of tracks and switches to get it to the place where it's needed. A factory will typically have a range of freight cars on site, both loaded and empty cars used for raw materials and finished products, waiting to be loaded, unloaded or taken away. Even with loops and switches, using a ("track-bound") locomotive to move one freight car could require moving a lot of other cars just to get the locomotive to the right location. Ssscienccce (talk) 15:57, 23 September 2015 (UTC)