Super sniffers: from sniffing out bombs to detecting cancer, dogs are working to save people's lives

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Author: Amy Barth
Date: Sept. 1, 2014
From: Science World/Current Science(Vol. 71, Issue 1)
Publisher: Scholastic, Inc.
Document Type: Article
Length: 1,694 words
Content Level: (Level 4)
Lexile Measure: 1110L

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At first glance, 2-year-old Tsunami seems like most other German shepherds. But her focus and intelligence have landed her in an elite squad of pups. At the Penn Vet Working Dog Center (PVWDC) in Philadelphia, Pennsylvania, she's learning to save lives.

All 17 dogs at the PVWDC are named after dogs that helped look for victims following the September 11, 2001, terrorist attacks on the U.S. Dogs have an astounding sense of smell, or olfaction, that allows them to excel at search-and-rescue operations. It also enables them to detect bombs and even sniff out chemical changes resulting from certain medical conditions, like cancer and diabetes. The PVWDC is training dogs to save people in these life-threatening situations.


The dogs begin training when they're 2 months old. They live with foster families that drop them off at the center from 9 a.m. to 5 p.m. every weekday, just like kids going to school. Trainers play hide-and-seek with the puppies to fine-tune their sense of smell. They teach the dogs to climb stepladders and run past obstacles. They also expose them to loud noises so they don't get startled when emergency sirens go off.

"We give all of our dogs a general education, and eventually they get to 'pick a major,'" says veterinarian Cindy Otto, founder of the PVWDC. "More athletic, outgoing dogs tend to go into search and rescue. The quieter ones do better in calmer environments like medical detection."


Bombs, blood, and even diseases have specific chemical signatures, or chemical makeups. Every chemical signature gives off a different smell. Although the smells are usually too subtle for human noses to detect, dogs can tell something's wrong and alert people of a problem by barking or pawing.

Many people have reported that their dogs alerted them to an illness. The dogs would whine or continuously nudge somewhere on their owners' bodies. Owners would dismiss the behavior only to be diagnosed later with cancer where their dogs had been prodding.

Now, scientists are formally training dogs to detect disease. At the PVWDC, Tsunami is being trained alongside two other dogs to recognize ovarian cancer, a disease that affects the female reproductive system.

Tsunami sniffs a wheel that's like a small merry-go-round. Blood samples from different people are attached to the outside of the wheel. Blood from a person with ovarian cancer has a slightly different chemical signature than blood from someone without the disease. Tsunami must figure out which sample to pick.

"Both samples smell like blood and both smell like people. There's just a tiny difference," says Otto. When Tsunami reaches the ovarian cancer sample, she sits. With less than a year of training, she's correct about 90 percent of the time. Otto suspects dogs need roughly a year to master cancer detection.


One reason dogs excel at cancer detection is that their sense of smell is about 10,000 times as sensitive as a human's (see How Fido Follows His Nose, p. 21).

The PVWDC is working with scientists to design an electronic nose that can sniff out cancer. "We don't have technology that does what a dog or human nose can do," says University of Pennsylvania physicist Charlie Johnson, who is developing the e-nose. "Microscopes help us see better, hearing aids boost sound, but we're less advanced when it comes to improving our sense of smell."

Today, ovarian cancer, like many cancers, usually isn't discovered until the patient starts to experience pain or other symptoms. Then doctors use imaging equipment to see if there are tumors. The hope is that one day, Johnson's e-nose may be able to detect cancer in its early stages during a routine doctor's visit.


To make an e-nose that recognizes ovarian cancer, chemists need to figure out what molecules are emitted from the cancer. At his lab at the Monell Chemical Senses Center in Philadelphia, chemist George Preti creates different mixtures to try to match the cancer's odor signature. To do that, he warms a blood sample from a patient. This gives odor molecules in the sample more kinetic energy, or energy of motion, and they begin to evaporate from the sample into the air. "It's like when you heat up coffee and you suddenly start to smell its aroma," says Preti.

Then he uses a device to collect and identify odor molecules hovering just above the sample. Based on the molecules he collects, he can attempt to create a mixture that has an odor chemically similar to that of the ovarian cancer blood samples.

PVWDC trainers will add Preti's mixture to the wheel for the dogs to sniff. If Preti's mixture has a nearly identical odor signature to the cancer sample, it'll be tough for the dogs to tell the difference.

Once Preti perfects which molecules match the cancer's odor signature, Johnson's e-nose could be designed to detect that combination. "With the dogs' help, someday there could be an electronic nose to detect many different cancers," says Johnson. "It could sniff out diseases before the patient notices any symptoms."

Caption: DOG DETECTIVE: Tsunami sniffs a blood sample on the cancer detection wheel.

Caption: SEARCH AND RESCUE: A dog trains to find a person hidden in a rubble pile.


Why are dogs able to detect the smell of cancer but humans cannot? How could that ability help save lives?


A dog's sense of smell functions similarly to ours. The main difference is that a dog's nose is much more sensitive.

1 When a dog sniffs, air is sucked into its nose.

2 Airborne odor molecules enter the dog's nostrils.

3 The odor molecules travel to a membrane, a thin layer of tissue, that covers a bank of scent cells. There the odor molecules bind to the scent-receptor cells.

4 The receptor cells send electrical impulses to parts of the brain that decode what the smells are.


Lexile 1130



Grades 5-8: Structure and function in living systems

Grades 9-12: Behavior of organisms


LS1.A: Structure and function


Literacy in Science: 8. Distinguish among facts, reasoned judgment, and speculation in a text.


Learn how dogs' amazing sense of smell is being used to find new ways to detect cancer.


1. Turn to page 20 in the digital edition at www.scholastic .com/scienceworld and have students do the same in their magazines.

2. Read the headline and subhead aloud. Ask students to predict what the article will be about. How do they think dogs could detect cancer?

3. Separate students into groups of 2 or 3. Ask them to quickly look over the subheadings, photos, and diagram. Based on what they see, ask the groups to write 5 questions about the topic. Then have them read the article in their groups. They should record any answers they find in the text.

4. Reconvene as a class and discuss their reactions to the article. Were they surprised to learn that dogs could smell cancer? Do they think there will be a cancer smell test in the future?

5. Discuss the questions and answers from each group. Ask students to read aloud any questions they had that weren't answered in the text. Discuss whether they can predict the answers based on what they learned in the text.

6. Have students do research to find answers to the leftover questions. How do the answers match up to their predictions?


What are some other ways humans have made use of the skills of animals throughout history? (homing pigeons find their way home and were used to carry messages; dogs are territorial and are used to guard property; some animals are strong and carry heavy loads; etc.)


Assessments are tailored to different science disciplines and the Common Core State Standards. You can find this entire assessment package by going online to and entering the digital edition. Simply click on the skills sheets button found on page 20.



Have students use this skills sheet to analyze statements related to the article and determine if they are facts or opinions.



Students will learn about the medical imaging techniques currently used to detect cancer with this reading-comprehension activity.



Have students try this fun hands-on to see how well their sense of smell stacks up!



To encourage critical reading, use this reading passage about the work of search-and-rescue dogs after a major U.S. tornado.


* VIDEO EXTRA: Watch a video about a dog's sense of smell at

* Learn more about the olfactory system and try an activity to find out how the sense of smell can become fatigued:

* Check out this site to learn about an organization working to create canine smell tests for cancer:


NAME: --

DIRECTIONS: Answer the following questions in complete sentences.

1. According to Otto, what are the best characteristics for a search-and-rescue dog? --

2. Describe how a dog's olfactory system works. --

3. How do doctors usually detect ovarian cancer today? --

4. Explain the process Preti uses to try to collect the odor signature from ovarian cancer. --

5. How will Preti know when he has collected the molecules that match the cancer scent? --


1. According to Otto, an athletic, outgoing dog is often best for a search-and-rescue animal.

2. Odor molecules enter through the dog's nostrils and travel to a membrane in the dog's nose. There, they bind to scent-receptor cells, which send electrical signals to the dog's brain. The brain interprets the odor.

3. Today, ovarian cancer is normally detected using imaging equipment to find tumors.

4. Preti heats up blood samples to cause odor molecules in the sample to evaporate. Then he collects and identifies the molecules hovering in the air above the sample.

5. Preti will know he has collected cancer odor molecules when the working dogs can't tell the difference between a cancer sample and a fake.

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Gale Document Number: GALE|A386744293