Science and Medicine: Melamine
Tuesday, May 8, 2007; 11:00 AM
Washington Post staff writer David Brown and scientist Robert Poppenga were online Tuesday, May 8 at 11 a.m. ET to discuss melamine, the chemical culprit that's behind the pet food scare.
Dr. Poppenga is a board-certified veterinary toxicologist and is currently a professor of clinical veterinary and diagnostic toxicology at the University of California at Davis. He is also the section head of toxicology at the California Animal Health and Food Safety Laboratory and has been actively involved in investigating pet and livestock exposure to melamine and other contaminants found in wheat gluten and rice protein concentrate imported from China.
A transcript follows.
David Brown: Welcome readers and chatters. This is the chat about the science behind the recent pet-food poisonings. The point of departure is a story that appeared in Monday's Post about melamine and cyanuric acid and their probably interaction to form kidney or bladder stones and kidney failure in some animals. We are extremely fortunate to have with us Dr. Robert Poppenga, a veterinary toxicologist at the University of California, Davis. He will do most of the answering, although I will do some chiming in. We appreciate his being here greatly.
Fairfax, Va.: Hello,
How poisonous is melamine? Now people talk about melamine as if as deadly as cyanide. Is melamine a common cabinet finish in every household? The cats and dogs could have scratched it off in our kitchens and ate it anytime.
Robert Poppenga: Melamine is not considered to be particularly poisonous based upon experimental work done in mice and rats. Cyanide is much more toxic than melamine. It is not considered to present a significant hazard to human health either. Unfortunately, there is little toxicity information that is specific to dogs and cats, although many years ago it was given to dogs to see if it would be an effective diuretic (increase urine production). At that time, no adverse effects were noted.
David Brown: I believe that cyanuric acid, which is a compound also found in some of the crystals of the affected animal, is believed to be somewhat more toxic to animals, although its effects on dogs and cats specifically is similarly unknown.
Silver Spring, Md.:
Does food agency has a conculsive evidence to say that pet deaths are due to Melamine or its congeners.
What is the purpose of adding Melamine in pet food?
Robert Poppenga: It is unlikely that melamine itself is causing the pet illnesses. The current thinking is that melamine in combination with cyanuric acid (another contaminant in the wheat gluten and rice protein concentrate used in the pet foods) may be responsible, although this has not been proven. There is no reason to add melamine to pet food - melamine is believed to have been added to the wheat gluten and rice protein concentrate to artificially increase their content of nitrogen (and as a result their apparent protein concentration). The more protein in the material, the higher the selling price.
David Brown: I think everyone is pretty confident in saying that melamine and the other compounds were not put in pet food for a purpose that was not, at base, fraudulent, deceptive, or possibly accidental. There was no high-minded "purpose."
Washington, D.C.: Is it safer to use pet food manufactured by a company that doesn't outsource?
Robert Poppenga: Good question. I believe that the food supply in developed countries (i.e., the U.S., Canada, Europe) is more tightly regulated and therefore much less likely to be adulterated than in other countries with fewer regulations and oversight. The problem would probably be finding out where the ingredients in a product originated from since that information is not on the label.
San Antonio, Texas: Greetings! Thank you for the webcast!
I have two questions:
Question 1: Were the fetus or new borns of the contaminated pigs/hogs checked for melamine, cyanuric acid, etc?
Question 2: How much melamine, cyanuric acid was found in the eggs of chickens?
Robert Poppenga: I can only address the pigs that were exposed in California. They were not pregnant so no fetuses or neonates were exposed. I do not have information on the other pigs that were exposed. I am not aware that anyone has tested eggs from chickens; I believe that the majority of chickens were broilers (i.e., raised for meat and not eggs).
Lovettsville, Va.: The term "contaminated" has been repeatedly applied to pet foods containing the chemical melamine. However, I have read that the chemical was deliberately added to pet foods to increase the products APPARENT protein content, as the assay for protein is based on an analysis of amines presumed to be derived from protein. If the melamine was added with the intent of making it appear that the foods contained more protein than actually present (i.e. with fraudulent intent), then the term "adulterated" would be more appropriate. If true, we should not tip toe around in an effort to protect the perps.
Robert Poppenga: The use of contaminated vs. adulterated really indicates the same thing; from a regulatory standpoint, food products containing melamine (or any other unregulated chemical) are indeed "adulterated".
David Brown: I agree that "adulterated" is the more precise term.
Shippenville, Pa.: Could the presence of cyanuric acid along with the melamine in the sick animals' bodies be that cyanuric acid is one of the metabolites of melamine and thus forms within the body, rather than coming from an external source? I read about that hypothesis two weeks ago.
David Brown: My understanding is that cyanuric acid is not in a pathway in which vertebrates chemically alter or breakdown melamine. I have heard the theory that cyanuric acid can be made from melamine by microbes, but I have to investigated that claim or done any reporting about it. Melamine and cyanuric acid are on each other's synthetic pathways, that is to say, they are easily changed into each other in chemistry labs and chemical factories.
Robert Poppenga: There is relatively little information regarding melamine metabolism in the body. However, there is one study in male rats that showed no significant metabolism.
The other point to make is that both melamine and cyanuric acid were identified in the wheat gluten and rice protein concentrate implicated in the pet food contamination.
Cecil Fox, Little Rock, Ark.: We are getting closer. Analysis of food and food products is in the purview of the AOAC (Association of Official Agricultural Chemists). They issue a methods text now in its 11th edition. This "bible" like the other one is fraught with anachronisms and archaic ways of analyzing foods.
From the FAO:
"For many years, the protein content of foods has been determined on the basis of total nitrogen content, while the Kjeldahl (or similar) method has been universally applied to determine nitrogen content (AOAC, 2000). Nitrogen content is then multiplied by a factor to arrive at protein content. This approach is based on two assumptions: that dietary carbohydrates and fats do not contain nitrogen, and that nearly all of the nitrogen in the diet is present as amino acids in proteins. On the basis of early determinations, the average nitrogen (N) content of proteins was found to be about 16 percent, which led to use of the calculation N x 6.25 (1/0.16 = 6.25) to convert nitrogen content into protein content."
The result has been that analysis of proteins languishes with a brewery procedure from the 1880s. The reason for this lugubrious progress is that the equipment is simple, he reagents are inexpensive, and it works except for more sophisticated adulteration with things like melamine.
The solution is to revise the AOAC Methods to include a more robust measure of protein or amino nitrogen and to ensure it is used. The problem here is that it often takes peons for an analyticle procedure to become validated by the AOAC.
Another issue is other adulterants that may be used that also give a Kjeldahl result such as chicken feces (patented as a feed for chickens), offal, feathers, hair, toe nails, and horn. The answer is simple enough, a greater investment in analytical methods and apparatus and speedier adoption.
Robert Poppenga: Good point. Many "official" analytical methods are antiquated and there needs to be a streamlined process for validating new methods and making them widely available.
David Brown: Peons working for eons---it is a recipe for regulatory inaction!
My understanding is that many chemical analyses are slightly more sophisticated than just measuring total nitrogen content of a substance, which is what the Kjeldahl reaction does. Many also measure urea nitrogen and subtract the two, coming up with a nitrogen content that is then assumed to be protein, although neither of the reactions actually measure the presence or number of peptide bonds, which is the hallmark of proteins.
Tulsa, Okla: Has melamine been proven to cause the kind of illnesses and deaths noted in the pets?
Robert Poppenga: The short answer is that no, melmaine alone has not been shown to be solely responsible for the kidney damage.
Anonymous: I've heard that there have also been problems with the Chinese food-supply chain involving substitution of food product (gelatin I think) with antifreeze. Some have suggested that this is also an issue with this pet food problem. Number one, is there any truth to allegations that Chinese food stuffs have been contaminated with antifreeze (ethylene glycol) and number two, could this same contaminant have any role in this pet food issue?
Robert Poppenga: The pet foods have been tested for antifreeze and found to be negative, so that is not an issue with the pets (antifreeze does cause renal failure). I have not heard anything about any other food product being contaminated with antifreeze. In the last couple of days there has been concern over the addition of diethylene glycol to cough medicines in lieu of glycerol. Diethylene glycol can also damage the kidneys.
Harrisburg, Pa.: I have been doing some research into this subject. I was told by experts at the Agriculture Department that it is impossible to test for most toxins in the food supply, and that the only way these toxins could be identified is to wait for someone, be it people or animals, to get sick and then use the symptoms of their illness to reduce the search criteria. Then they conduct the search to discover which toxin is causing the illness. Does this sound correct to you, or are they passing off responsibility on what information that prior testing of food could yield?
Robert Poppenga: The problem is that there is no simple, single method for detecting every possible chemical. However, there is likely to be heightened surveillance as a result of this incident.
Washington, D.C.: I've got some melamine bowls and a Mr. Clean magic eraser, which I understand is made from melamine. Do I need to worry about using either of these around my cats?
Robert Poppenga: No, there would be almost no exposure from those sources for pets.
David Brown: There are 674 melamine items on sale on eBay at the moment. I think we're safe saying that melamine bowls have a long record of safety.
Lumberton, N.J.: Thank you for doing this chat! I think the question most on my mind is: if a pet ate the contaminated food, would it cause long-term health risks? Assuming the cat didn't die, could it be permanently affected by the poisoning? And could there be additional problems that appear later on?
Robert Poppenga: I do not believe at this time we know the answer to that question. The kidney has a tremendous reserve capacity and hopefully exposed pets will not have long term consequences.
Washington, D.C.: Although my question is related to people and not pets, I'd like to ask if you have any comment on an incident reported recently in which glycerin exported by a Chinese company killed and sickened many people in Panama after it was mixed in with various medicines. The company apparently claimed that the glycerin was pharmaceutical-grade, when it actually was industrial-grade and poisonous to people. This incident, together with the recent pet-food poisonings and lead-filled baby bibs made in China and sold at Wal-Mart, makes me wonder what we as consumers can really do to protect ourselves from dangerous Chinese products. How can we make our government regulate products that could be dangerous to us? Do you think government agencies will wake up and realize how enormous the threat is to our health and our pets' health? (Granted, I'm not sure if the tragedy that occurred in Panama could occur here, but at this point, I think it is entirely possible.)
Robert Poppenga: I think that if there is any "silver lining" to the whole pet food recall, it is a recognition on the part of regulatory agenices that in a global trade environment, our food supply is particularly vulnerable. Unfortunately, resources have not kept pace with the need and most attention has focused on infectious agents coming into the country. Perhaps there will be more resources directed toward surveillance and test development.
David Brown: It will be interesting to see if all kinds of money for the surveillance and testing of food, and possibly even the inspection of Chinese manufacturing plants, will materialize when this is all over. The 9/11 events and the anthrax letter attacks caused a great flow of attention and resources to various aspects of public health and disaster readiness. This obviously is not on that scale, but it may nevertheless have some effect on where the federal government is willing to spend our money.
Downtown, D.C.: My young dog died from liver failure about a week before all the recalls hit the news. Tests showed his kidneys were functioning right up until we had to euthanize him.
Could melamine be the culprit here, or is there no chance of a failing liver but healthy kidneys? After euthanizing our dog, we had him cremated so there is no way to test his remains for this poisoning.
Robert Poppenga: There is absolutely no evidence for the recalled pet food affecting liver function...only the kidneys are damaged.
Gaithersburg, Md. Pet ER Trip: Thank you for addressing this topic. I spent hours in an emergency clinic after my cat became lethargic and a food he was eating got recalled. Please advise us on how to recognize the clinical signs of possible toxicity, and how we can protect our animals. I have spent more time researching pet food than food for the rest of my family. Also, I fear cross contamination from non-recalled foods processed at the same facilities as recalled foods. Surely, the machines cannot be completely sterilized between food runs.
Robert Poppenga: The clinical signs exhibited by affected pets are very non-specific (i.e., they could be caused by many diseases). Pets will perhaps first be noted to have vomiting and are not eating. They may drink more water or urinate more than normal. They would then become very lethargic and inactive. Your veterinarian would have to run tests to determine that the kidneys were not functioning or whether there was some other cause of the pet's illness. I can say that most pet food manufacturers employ rather strict protocols as far as the food processing goes. I think that any substantial cross contamination would be unlikely.
David Brown: There is also a dose issue. Neither melamine nor cyanuric acid are poisonous in low doses the way cyanide is. So the idea that some adulterated food that might remain on the mixing blades in some big vat in a pet-food factory could alter the food in the next batch in a way that would have an actual health effect---I think the feeling is that is not likely and is not worth worrying about.
Baltimore, Md.: In simplest terms, is there some way to be sure the food we feed our dogs and cats is safe: Either by consulting an online list of products or looking at the ingredients on the side of the bag? THANK YOU in advance.
Robert Poppenga: First, check the manufacturer's website for the recalled pet foods (which might include a lot number or date). I believe at this point, that the chances of still having unidentified, contaminated pet food on store shelves is low.
Three ingredients have been shown to be contaminated: wheat gluten, rice protein concentrate and corn gluten (in South Africa). You can check the labels for any of these ingredients and avoid them to be safe - there are lots of pet foods that do not contain them. Home cooking is not generally recommended unless you are working with your veterinarian or veterinary nutritionist to make sure that the diet meets the nutritional needs of the pet.
Philadelphia, Pa.: If we start feeding our dogs and cats "human" food, what kind of viaman suppliments can we give them to go with it?
Robert Poppenga: See a previous answer...you would need to work with your veterinarian or veterinary nutritionist to make sure the diet is adequate.
Washington, D.C.: Is it safe to say that the introduction of the nitrogrin-enhanced compounds are done soley for marketing reasons? or do they help in creating a more nutritious product?
David Brown: A substance that boosts nitrogen would only be useful if the nitrogen were biologically available to the consumer. My understanding and research suggests strongly that the nitrogen in melamine--six atoms in a 15-atom molecule--is not biologically available (or very little is), as most of the compound is excreted chemically unchanged.
I suppose another issue is whether there is any need to boost protein in pet foods. There is a fair amount of evidence that most human beings consume far more protein than they need for health and sustenance.
Robert Poppenga: I agree with David's comments. Melamine does nothing to enhance a food's nutrition.
Chicago, Ill.: How can the assessment that melamine, whether in combination with cyanuric acid or not, is responsible for the recent deaths of pets be reconciled with the USDA/FDA's statement yesterday that melamine and related compounds at the levels detected in pet foods present little or no threat in food?
Robert Poppenga: This is a good question. I believe that the FDA/USDA risk assessment pertained to the pigs and poultry exposed to small amounts of the pet foods (the pig and poultry diets contained melamine at much lower concentrations than the pet foods because they made up only a small percentage of the diets). So the conclusion was that meat from pigs and poultry contained such low concentrations of the contaminants that there would be essentially no risk to people eating the meat.
David Brown: Again, dose and length of exposure are likely to be very important in determining whether an animal (including a human animal) would get sick from these compounds.
Washington, D.C.: What are some of the signs that my pet might have been affected by the contaminated food? My cat passed away about a month prior to the recall announcement. During his last vet examination, he was deemed healthy. I was there to witness my pet die: it looked like he was choking and having a seizure. Twenty minutes later as we rushed him to the clinic, he passed away. Doctors said he did not choke on anything and that it might have been a heart condition, but no autopsy was performed. In hindsight, I should have requested one.
Robert Poppenga: Ideally, a necropsy (autopsy in human terms) is always the best way to try to figure out a cause of death if it is not evident before death. The signs that you describe to not seem to fit what has been typically described in pets affected by the pet food.
Tribeca, N.Y.C.: Thank you for taking my question. The scale of this pet food recall just boggles my mind. Do we have any idea how long this has been going on and the true extent of it?
I have been making my Westie her own food. I boil ground beef, cuts of lamb shank with carrots and peas. Nothing else. Once it is done I strain it and put it in the food processor. When I feed her I mix that with some dry food (non-recalled). Do you think she is getting enough nutrients? I am amazed how she can eat around the dry food and snarf down the homemade food.
David Brown: FDA officials have said they have no idea of whether this has been going on for a while. I do not know whether pet-food manufacturers archive samples of every lot, which could now be tested. It's a good question. I think the fact that the adulteration caused a detectable "signal" in terms of animal health in several regions at the same time suggests (indirectly, of course) that this is a sporadic event and not likely to be a chronic state.
Robert Poppenga: It is my understanding that there is certainly interest in testing archived ingredients if available to try to ascertain if this was a more longstanding contamination issue....the limiting factor will be the availability of older samples for testing.
Rockville, Md.: How long will it take before all the tainted chickens are eaten and thus, off the market? Is the FDA taking it's current stance based only upon the science, or is it releasing the chickens based upon a "business friendly" policy? I read about "minimal risk" but what is the risk?
David Brown: There are no certainties in any of these issues, only probabilities. Might a few freezers contain one of the 2.7 million chickens that got some adulterated pet-food scraps and went on the market in March? Possibly, but most such products are consumed soon after purchase, so they are long gone. They would have contained little melamine, as most of the compounds is excreted unchanged by the body, and the exposure would have been brief. So the likely risk to human health is very, very small--and there have been no unusual spikes of human illness suggesting there was any health effect at all.
Arlington, Va.: Is Melamine a relatively new additive to pet foods? And if not - why is it NOW - becoming such a problem?
Robert Poppenga: Melamine should not be in pet foods (or any food for that matter). Pet food contamination and associated pet illnesses were first recognized in March, thus the whole concern about melamine. In tracing the contaminated pet foods, their use in pig and poultry feed became evident.
Washington, D.C.: OK, so we check the label. But what assurance do we have that the label is truthful and accurate?
Robert Poppenga: Well, the only thing that I can say is that (in theory at least), pet food labels are tightly regulated as to the product's ingredients. I cannot answer the question of the current degree of oversight by the FDA, but the regulations exist.
David Brown: Alas, I think we have run out of time. I know there are quite a few questions left. I'm sorry we couldn't get to them, although some were left unanswered because we don't have the answers (or even reasonable guesses!) Thanks for reading and listening. I think we can agree that we were lucky to have Dr. Robert Poppenga with us this hour.
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