Home > Public / Media > Ask a Toxicologist


Have a toxicology related question? Can't find the answer? !

Your source for personal toxicology information.
The “Ask A Toxicologist” program is part of a growing effort by the College to improve public awareness and education regarding the toxicity of medication interactions, occupational chemicals, new drugs of abuse, venoms and plant toxins. The goal of the program is to provide rational, evidence-based answers to common medical toxicology questions – clearly and concisely. Members of the public are encouraged to submit questions through  for review by a panel of experts in human poisoning, who will post a consensus opinion written by one expert in the field. There is no charge for this service.
Questions relating to an individual’s health concerns cannot be answered, as the program cannot create or replace a doctor-patient relationship. Additionally, we are unable to provide counsel, advice or interpretation for any legal issue. Questions and answers should be of a general nature, and of interest to a wide population. Not all questions will be able to be addressed.

Ask A Toxicologist

What are the potential health effects of working with the herbicide glyphosate, contained in products such as Roundup®?

posted on 4:31 PM, July 22, 2014

Roundup® is the trade name for one of many products that contain a chemical called glyphosate. Glyphosate is an herbicide, which means that it is used to kill plants, typically weeds. Glyphosate works by interfering with a plant enzyme that makes proteins necessary for a plant’s survival. When this enzyme is blocked, the plant cannot grow and dies. Humans do not have this enzyme and are immune to this effect of glyphosate.

When someone has intentionally ingested glyphosate in an attempt to hurt themselves, or when they have been exposed to large amounts of highly concentrated glyphosate, toxicity has been described. The toxicity usually results from the other components of the herbicide product, mainly the chemicals used to stabilize the glyphosate and allow it to be applied onto fields and crops. Symptoms that may occur after ingestion include nausea, vomiting, and diarrhea. In cases of severe toxicity, as might occur after intentionally drinking concentrated glyphosate, low blood pressure, abnormal heart rhythms, kidney, liver, and lung injury, and even death can occur.

If people use a glyphosate-containing product at home and are exposed to small amounts on their skin, eyes, or mouth, they should immediately rinse the area with water. There may be a minor reaction that looks like irritation with some redness. Products that are sold for home use contain lower concentrations of glyphosate that are generally believed to be safe. Additionally, there do not seem to be any long-term health effects from this chemical. In animals exposed to large quantities of glyphosate there was not an increased risk for cancer.

Overall glyphosate used at home is generally safe. Severe toxicity results from intentional ingestions of the concentrated formulation, not from casual exposures. In cases of small exposures to the skin, the eyes, or the mouth, the area should be washed thoroughly.
The Ask A Toxicologist Team

How are urine tests for drugs of abuse performed?

posted on 9:50 AM, June 11, 2014

Drug tests can be performed on blood, hair, saliva, urine, and nails. Urine is frequently used, as it is easy to collect, and drugs and their metabolites are concentrated in the urine, allowing for a prolonged period of detection.There are two main types of urine drug tests: immunoassays and gas chromatography mass spectrometry (GC-MS). Immunoassays work by using antibodies to check if the original drug or its breakdown products are present. The antibody is designed to bind only to a specifically shaped molecule. These tests can be run quickly and inexpensively. They are the tests most often used in employment and medical settings. GC-MS is a method that identifies a specific compound within a sample, like a fingerprint. It is more accurate than immunoassays, but much more expensive and time consuming to run. It is often used as a confirmatory test after a positive immunoassay.

What are the problems with these tests?

False positives are a well-known problem with immunoassay based urine drug tests. The antibody used in these tests is designed to bind to a specific molecule shape. If there is another drug or substance that has a similar shape, it may be able to bind to the antibody. Therefore, the test will be positive, but falsely, as the antibody did not bind the drug in question, but something with a similar shape. The false positives for each urine drug test are different and must be considered when interpreting a result. False negatives are another common problem. A false negative is when the drug of concern has been used, but the test does not detect it. This can occur for a variety of reasons - the test, the drug, and the patient. Some variables include when the drug was ingested, how much of the drug was ingested, what the cut-off for detection is for the test, the concentration of the urine, and if there were substances added to the urine to tamper with the test.

How long will a urine drug test stay positive?

There are many factors that affect how long a urine drugs test will stay positive. A few examples include frequency of drug use (short term versus long term), the specific drug used, whether the drug accumulates in the body, and if there are metabolites of the drug that are detected by the test.

Urine drug tests are complex, but understanding these fundamentals can help to simplify them. Caution should be used when interpreting any urine drug tests, and it should only be done by a medical professional with the appropriate knowledge and experience.

Navneet Cheema, MD
view archives archives
RSS rss