Threat Detection, the Exposome and Olfactory Awareness

Global pandemics are real good for motivating exposure scientists to identify threats in the environment. Add to that the threat detection capabilities of chemosensation (smelling), and you've got some ingredients for a burgeoning field of study that overlaps with olfaction-inspired technologies.

 

Olfaction is for threat detection perhaps above all things, so it is fitting that we see this application become more common. One common use already being implemented by the company Aclima is the distributed air-quality sensor network for pollutants:

 

Early warning sensor sniffs out cities' harmful gas

May 2020, phys.org

 

The IGZO thin-film transistor acts as both an electronic component of the device and also as the NO2-sensing layer. The strongly electron-accepting NO2 molecule is drawn to the electrons on the transistor's surface. The more NO2 molecules that adhere to the IGZO, the more electrons are depleted from its surface, altering its electronic output and triggering an NO2 detection alert.

 

After a detection event, the sensor is reset by reviving the IGZO layer with the light from an integrated blue LED. Similar to a solar cell, the light generates negatively charged electrons and positively charged holes in the IGZO, which neutralizes the adsorbed NO2 and releases it from the surface. "This is the first study to achieve sensing and revival of a semiconducting metal oxide-based thin-film transistor sensor at room temperature," says Surya.

 

*Nitrous oxides (NO2) are a by-product of burning fuel, just like carbon monoxide, carbon dioxide, and sulfur oxides, and all of these are harmful to human health.

 

And here's another related report:

Aerosol-printed graphene unveiled as low cost, faster food toxin sensor

June 2020, phys.org

 

Researchers in the USA have developed a graphene-based electrochemical sensor capable of detecting histamines (allergens) and toxins in food much faster than standard laboratory tests.

 

The team created high-resolution interdigitated electrodes (IDEs) on flexible substrates, which they converted into histamine sensors by covalently linking monoclonal antibodies to oxygen moieties created on the graphene surface by a CO2 thermal annealing process.

 

As an additive manufacturing method that only deposits material where it is needed and therefore minimizes waste, aerosol-jet-printed sensors are low-cost, straightforward to make, and portable. This could potentially enable their use in places where continuous on-site monitoring of food samples is needed to determine and maintain the quality of products, as well as other applications.

 

-Aerosol-jet-printed graphene electrochemical histamine sensors for food safety monitoring, 2-D Materials, DOI: 10.1088/2053-1583/ab8919

 

And still further sensorific developments:

Paper-based device provides low-power, long-term method for analyzing sweat

June 2020, phys.org

 

Using a process known as capillary action, akin to water transport in plants, the device uses evaporation to wick fluid that mimics the features of human sweat to a sensor for up to 10 days or longer.

 

"We expected that the flow of the model sweat will be suppressed by the deposition of a salt layer inside the drying pad," Velev said. "By following the flow of model sweat, we found, quite surprisingly, that such a simple paper construct can achieve continuous sweat pumping and disposal for very long periods."

 

"The biological markers or drug metabolites that seep in the patient's sweat over a long period will be captured on the paper pad and preserved in a time-stamped manner to be analyzed later, similar to tree rings preserving the record of tree development," Dickey said.

 

-Principles of long-term fluids handling in paper-based wearables with capillary-evaporative transport, Biomicrofluidics (2020). aip.scitation.org/doi/10.1063/5.0010417

 

Post Script:

The exposome - When our environment drives health and disease

May 2020, phys.org

 

From this press article: The exposome is the sum of all the environmental drivers of health and diseases: a combination of external factors such as chemicals contained in the air, water or food, and of internal components produced by our organism in response to various stress factors.

 

Notes:

Aclima delivers hyperlocal air pollution and climate emissions intelligence at unprecedented block-by-block resolution.

 

 

 

Olfactory Remains

The picture seen here is taken from a local Arizona news source circa 2014, attached to an article citing the decrease in “migrant deaths” in the Arizona desert at that time. That data was given by Border Patrol. They say most of the deaths are caused by the heat.

But this post isn’t about migrant deaths; it’s about olfactory forensics, using one’s sense of smell to find decomposing bodies.

On the other side of the United States/Mexico border, deaths aren’t from heat, and the bodies are not of migrants. They’re people suspected to have been kidnapped by drug cartels, either for ransom, recruitment, or rivalry. Then there’s the women, who are abducted for trafficking. For whatever tragic fate befell them, their bodies are buried in a clandestine grave.

When farmers and cowboys find bones in the brush, they notify The Searchers of El Fuerte, who investigate suspected burial areas. They dig the earth, and then sniff the air. If they find bodily remains, they take them and send them for DNA testing. If a match is found, they try to inform their relatives.

It may sound primitive, but this is common practice. The human nose is the most powerful device we know of for detecting things that smell. It’s hard to believe, but it does explain why actual humans are hired to smell the fish at large industrial operations to make sure they’re fit for human consumption. It’s also why the fragrance industry employs noses. Shoot, Firmenich, who in 2017 was making 95% of the world’s supply of Hedione (which is in 95% of fragranced products) employ their own truck drivers, custodians, and administrative assistants to assure the quality of their Hedione batches. (This is because so many people have a hard time smelling it; if you’re good at detecting Hedione, no matter what your actual job, you will be asked to sniff batches.)

Back to the bodies. As flesh breaks down, it produces a molecule called Cadaverine, which smells like rotten flesh. (If you’re not sure what that smells like, try driving past exit 14 on the New Jersey Turnpike sometime around August; that should do it.)

Eventually, the cadaverine subsides, leaving other equally offensive odors. There will come a time when a deterred body no longer produces a smell at all. Until then, it is a recognizable indicator.

Image source

Notes:

The Searchers - Mexican women who look for the dead

Dec 2018, BBC

Cadaverine has the sickly-sweet smell of rotting flesh

You Are Never Gonna Bereave This

Limbic Signal, 2017

What Exit - The Smells of the New Jersey Turnpike

Limbic Signal, 2016

Sensory Psychologist Avery Gilbert features the “I Smell Dead People” installments on his blog First Nerve

Post Script:

Body Farms are places where bodies are buried under all kinds of different conditions, to be examined at various stages of decomposition, for the purpose of aiding forensic anthropology. The information learned on these body farms could be useful for solving potential crimes or missing persons cases.

The Body Farm at the University of Tennessee’s Forensic Anthropology Center

At Your Fingertips

Condom-detecting fingerprint test 'set for court use'

Oct 2017, BBC

"[Your fingerprint] contains molecules from within your body but also molecules that you have just contaminated your fingertips with, so the amount of information there potentially to retrieve is huge."

-Dr Simona Francese of Sheffield Hallam University for the BBC

And this information is now set to be used in courtrooms.

It comes as a surprise to me that this technique is only being used now. We've known since the dawn of the microscope that the labyrinthine ridges of our fingertips are stuffed with bacteria and whatever else in the world we recently touched. We've also been using this mass spectrometer tool since the 1900's, which is also when fingerprinting itself came out.

I’m adding this to the archives here because the mass spectrometer, combined with the gas chromatograph, is the primary tool for detecting odorous molecules. It’s the closest thing to an artificial nose that we have, and it’s the only we to determine with certainty what’s in a smell.

I’ve added below a chart taken from Sigma Aldrich, a supplier of essential oils for the flavor and fragrance industry. It shows the fingerprint, if you will, of the smell of orange.

 

The smell of orange, as seen in gas chromatograph analysis, courtesy of Sigma Aldrich.

As you can see, the smell of orange has in it way more than just “orange.” In fact, there’s nothing called “orange” in there at all. Limonene and Citronellol might sound like they belong there, but the others are probably foreign to most.

image: Imperial College London site, where you can grow your own fingerprint bacteria on an agar plate 

Lo Fi Biometric Data

Missing Florida woman found after she bottled her scent

July 2017, BBC

Yes it’s true – you can swab your armpits, put that swab in a jar for the next twenty years, and eventually use it to find yourself amidst your own sliver alert (a public alert system for missing persons in the US).

If you haven’t read the 1985 olfactory crime thriller Perfume, you might not think the same thing when you read headlines like this. In the story, the main character with the nose of steel wraps bodies in a cocoon of fat-laced paper, absorbing the victim’s unique scent, and concentrating it into a kind of olfactive mind control substance that allows him to shapeshift his own persona while committing more crimes or just turning an entire town into an orgy.

Anyway, in the same era where employers are chipping their workers, and face rec algorithms are so good they can be used with as much accuracy as a fingerprint, it’s cool to see such simple methods for finding missing persons.

Post Script

 The conversation on my last date led to her revealing to me the secret techniques of pet detectives (yes they exist). Her cat escaped from her apartment, and never having been outside the apartment, could not figure out how to get back in. Turns out that what a pet detective does is have you piss in a bottle, then spill that bottle outside the front door to your apartment. It’s not enough that your neighbors will complain, but certainly enough that your cat will recognize it as a sign of home, and begin hanging out around where you spilled your piss, and eventually you will be reunited. (And probably because this is what I end up talking about on dates, I’m still single, no pet detective necessary to solve that one.)

image source: shutterstock