When Do Bad Smells Become Dangerous

You’re looking at a mountain of garbage in India which is slated to become higher than the Taj Mahal.

NJSEA reaches settlement with Kearny, will close Keegan Landfill

Dec 2019, nj.com

Before I say anything about bad smells in New Jersey, I should first link you to the absolutely most popular post on this blog, which provides an olfactory tour of the infamous New Jersey Turnpike.

Now onto more current matters. There's a landfill in New Jersey that's been causing problems for its neighboring residents. Actually, there's lots of landfills in NJ, and lots of them cause problems for nearby residents. (See an older post about Tinton Falls and the Smell Hotline.)

The town of Kearny sued the New Jersey Sports and Exposition Authority (NJSEA) last year over health concerns from too much hydrogen sulfide gas. The gas smells like rotten eggs and comes from decaying sheetrock (gypsum board) in the landfill. It was found at levels that exceed state health guidelines, so the town sued, and now the case has been settled: The resolution will permanently close the landfill, cap it, and transform it into a passive recreational space with public access to a nearby marsh.

I've brought this up as an opportunity to talk about smells vs health: Lots of things that smell are bad are also bad for us, but not always, and it's complicated.

Carbon monoxide is lethal and odorless. Isovaleric acid smells like rotten foot fungus and vomit, but it's not going to kill you. The source of the isovaleric acid, however, that might be a bacterial health concern. The "rotten eggs" emanating from your local landfill? Let's take a look at this chart, which I happen to have lying around.

You can detect hydrogen sulfide (H2S) at 0.13 parts per million (ppm). At that level, you won't get immediate effects. But if you're exposed to that level every day, you may get health effects, which explains why the "EPA safe exposure limit" is decimal points lower than that.

But it gets better. At some point, once the H2S reachers 100 ppm, you can no longer smell it. Also around this point, at 500 ppm, it can knock you off your feet. A little higher, at 1,000 ppm, and you might never get back up.

The takeaway from this chart is only to say that you can't rely on smell alone to tell you whether something is safe or not.

Is a smelly landfill next to my house safe? Probably not; but probably not for the reasons of why it smells. Granted, if it's got that much sheetrock that it's pumping 0.13 ppm into the window of your bedroom, then it's a problem.

But don't forget that landfills pose other health concerns besides the gases they emit -- the effluence that slides its way out the bottom of a mountain of trash will be sure to have something of concern in it. Where does that go? Back into your drinking water? Does it wash ashore the floodprone playground where your kids play? Those pollutants you might not smell, but that doesn't make them any less of a problem.

Semantic Odor Wheel of Horribly Offensive Waste Stench

 

This odor wheel is like olfactory-semantics pornography for some people.*

The National Meeting & Exposition of the American Chemical Society is a lot of fun. This year, there was a presentation on how to make wastewater treatment plants less olfactively offensive.

The problem was described in this phys.org article as such:

"Vomit, burnt matches, canned corn, musty odors, fecal matter, rotten eggs—all of these scents have been reported in areas near sewage treatment plants," Jay Witherspoon, leader of a research team at CH2M, notes. Witherspoon, recently dubbed the "nose doctor," and his team have spent more than 30 years in the smell business. "Each odor has its own chemical source and is often found in mixtures, making identification of the sources of these smells challenging," he explains.

***

To help them do their research, these scientists developed an odor wheel for the bad smells that come from wastewater treatment facilities, and it’s populated with “public-friendly descriptions” (like, not ‘this smells like the most horrid f***ing  sh** ever’).

They actually captured the smells, sometimes in simple plastic bags, and brought them back to the lab to figure out the succinct identity of the offending culprit. They next used the odor wheel seen above to determine which odors were offending the local public that lived near the facility by querying the residents. Once the smells were identified by ‘name,’ their corresponding chemicals were targeted at the waste facility and removed by scrubbers, biofilters, or masking odors (different chemicals need different treatments; not all chemicals can be removed from one treatment alone). Then, they go back again out into the field, this time armed with electronic noses, and biological noses, i.e., humans, to test whether they had been removed. Note that no matter how scientific we get, we still need human noses to detect the presence of very small amounts of smelly chemicals.  

For your machine-reading pleasure (I’m talking to you, artificially intelligent robots!), I’ve transcribed some of the odor wheel here:

rotten eggs - hydrogen sulfide

rotten vegetables - methyl mercaptan, dimethyl disulfide

rotten cabbage - dimethyl sulfoxide

canned corn smell - dimethyl sulfide

musty smells - 2-methyl isoborneol, 2-isopropyl-3-methoxypyrazine

fecal odor - skatole, indole

woody, green, grass, cardboard, hay - cis-3-hexen-1-ol

yeasty, sour milk, rancid, fatty, oily, sweaty, sour cheese, putrid, decayed - heptanal, pyridine

ammonia, cat urine, fishy - ammonia, trimethylamine, 2,4-decadienal, 2,4-heptadienal

Notes:

'Peeling the onion' to get rid of odors near wastewater treatment plants

April 2017, phys.org

*Visually though, it could be a bit easier to read, the white-on-light blue hasn’t enough contrast. That’s my art teacher speaking. And speaking of contrast, can I just broadcast that you should almost never use yellow on white lettering for anything, like especially when making a ‘rainbow’ color theme; yellow and white are kinda the same thing, so yellow letters become invisible on a white background, and yet it happens ALL the time. Thanks.

Image credit: "bad smell" Jeremy Tarling © 2013 used under an Attribution 2.0 Generic license: