Dr. David Carpenter is a Professor of Environmental Health and Toxicology in the School of Public Health at the University of Albany. He is also the Director of the Institute for Health and the Environment at the University of Albany.


What was the purpose of the farmed salmon study?

The purpose of the study was to determine whether or not there were hazardous contaminants in farmed salmon that would counterbalance the benefits of eating a fish that's high in protein and some essential fatty acids.

What were you looking at?

This was a very large study. We analyzed in the portion of the study that's in our publication over two metric tons of salmon. These salmon were wild Alaskan salmon from several places in Alaska and Northern Canada. They included salmon from eight major salmon farming countries purchased directly from the suppliers. They included salmon purchased in supermarkets in 16 cities in North America and Europe. In addition, we purchased salmon fish food from the two major suppliers that provide the majority of fishmeal and fish oil in the world.

What were you looking for? How many different toxins?

It's true that there have been three previous studies published in peer review publications plus a small report from the Environmental Working Group that demonstrated contaminants in farmed salmon. In none of these studies were there more than 10 fish sampled. In most of them, they were sampled only for one or two contaminants; primarily PCBs. Our results are consistent with the results of those other studies. But they're much more systematic - they're much larger. We analyzed for a much larger number of contaminants. We do our sample from most of the major farmed salmon regions of the world plus having analysis of the food. So I think that it's very difficult to criticize our results on the basis of size. This is a very large systematic study. We have analyzed for all of the major contaminants of concern.

Were there thousands of assays?

We purchased 459 fish from farms, and from those 459 fish we got 153 samples. In other words, we pooled several fish, ground them up, made a mixture and analyzed them as one unit. But it's a large number of fish. So, the procedure was we purchased 10 fish from each farm, and chose nine of them to make into composites of three fish each. So these are large salmon, and we tried to get salmon of more or less the same size from the different farms. In addition to that, for the supermarket samples, we went to 16 different cities in North America and Europe and in each city went to three different supermarkets where we bought supermarket salmon fillets - three different fillets from each supermarket and then ground them together.

Now, many times in the supermarket people didn't know where the salmon came from. If it says Atlantic salmon were pretty confident that it's a farmed salmon because there is no significant commercial harvesting of Atlantic salmon. Almost all of the farmed salmon are, in fact, Atlantic salmon. In some cases, people did know where the salmon came from but that was unusual. For the wild salmon, we purchased 135 salmon from suppliers of wild Alaskan and British Columbian salmon. These were handled in the same way. We made composites of three fish, ground them all together and analyzed them as one unit.

What about the fishmeal sample?

Well, the details about how they make the salmon feed, we don't really know in great detail. We purchased 13 samples of the feed that's fed to salmon. And they came primarily from Scotland, from British Columbia and from Chile. The production of fish food is a very international industry. And there are two major companies that control the lions' share of the world's market. Each of them, we expect, produce feed from regions in which it's marketed. So that the feed fed to salmon in the North Atlantic probably comes from trash fish from the North Atlantic. That from Chile probably comes from trash fish in the South Pacific. But we don't really know that. The point that is so clear from our study is that the contaminant loads in the feed fed to the farmed salmon is very similar to the contaminant loads that we see in the salmon that are farmed in that region.

What were the results of your study?

In this paper we report the analysis of 14 substances that fall into the category of persistent organic pollutants. These include PCBs, dioxins, and dioxin like compounds and 12 persistent pesticides, all of them chlorinated. The fact that they're persistent means that they're not easily degraded, either in the fish or in our bodies. They do last for a long time in the environment. Now, we found in general, that for 13 of these 14 substances, there were significantly higher levels in the farmed salmon than in the wild salmon. For most of them, it wasn't just a small difference; it was about a 10-fold difference in the farmed salmon.

We went on to do a careful analysis of four of them because of the fact that for these four there are advisories on fish consumption and health based indicators that have been developed and distributed by the Environmental Protection Agency and by the World Health Organization. The four are PCBs, dioxins, dieldrin and toxaphene. Dieldrin and toxaphene are pesticides that were used primarily in the South, but they distributed over the world primarily by spreading through atmospheric transport. We used EPA fish advisories that were originally developed for Great Lakes fish consumption for PCBs, dieldrin, and toxaphene. On the basis of these advisories, the most contaminated fish have such levels of containments that one should eat no more than one meal every other month.

Could you say more about the Great Lakes advisories?

EPA has issued advisories for the consumption of Great Lakes fish on the basis of PCBs, dieldrin and toxaphene. We applied these advisories in calculating the numbers of meals of farmed salmon that should be eaten per week from different places, from different countries, from different supermarkets. In the most severe restriction advice would be for salmon primarily from the Baltic Sea area - from Norway and Scotland, where the consumption should be limited to not more that one meal every other month. For all of the farmed salmon, there were significant advisories. Now we did find that the farmed salmon from Northern Europe was more contaminated than that from Chile or British Columbia. This probably reflects the fact that the food that's fed to farmed salmon in Northern Europe comes from the Baltic Sea, which is a highly industrialized area, and it's known to be quite contaminated. The food that's fed to the Pacific Ocean farmed salmon is less contaminated. However, for PCBs, dioxins and dieldrins, all the farmed salmon from Chile still had significantly higher levels than the wild Alaskan salmon.

If we calculate in terms of advisories on meals per month, or meals per week, for the wild Alaskan salmon up to eight meals a month is not dangerous on the basis of these EPA advisories. For the farmed salmon, there would be recommendations for restricted consumption even of the least contaminated salmon - those coming from Chile. The World Health Organization values for dioxin equivalents led to restriction advisories that were somewhat less severe than that for the PCBs, dieldrin and toxaphene. But in every case the same pattern was there. The wild salmon could be consumed with relative comfort that you're not getting significant numbers of contaminants, whereas the farmed salmon, including those from the least contaminated sites in Chile that we studied, there should not be unrestricted consumption of these fish.

Why do wild salmon have fewer toxins?

One conclusion from our study is that the source of the contaminants is the food that the farmed salmon are fed. This is not a totally negative conclusion because it means that we can get the contaminants out of the farmed salmon for the most part by finding a clean food to feed them. But the source of contaminants for wild salmon must also be primarily the food they eat. The reality is that wild salmon do eat small fish. They eat a lot of crustaceans; they eat a lot of shrimp. The color, the red or pink color of the wild salmon, comes from the food they eat naturally. This is unlike the situation with the farmed salmon where the color is an added dye. Because farmed salmon, if this dye is not added, have flesh color that's sort of a dirty gray. So the color that we see in the fillets in the supermarket is all an added dye.

Why are there less accumulated toxins in salmon?

Wild salmon do eat fish but they eat a lot of crustaceans. In fact the crustaceans, the shrimp and that sort of little animal is where the wild salmon get their natural pink or red color. The fish that they eat are lower on the food chain. They have fewer contaminants. But another conclusion from this that I think is very important is that we have sufficiently contaminated our oceans, that now if we concentrate the fish meal and fish oil from trash fish that nobody wants to eat, then shove it to fish in a cage and push their weight gain, we can develop animals that are dangerous to eat because of the accumulations of toxins.

Can you address the issue of fat content between farmed and wild salmon?

Well, farmed salmon have much higher fat levels than do wild salmon. I believe in our study it was a tenfold greater fat content. Salmon in general are a fatty fish and contaminants do accumulate in fat. However, even if one adjusts for the greater fat content in the farmed salmon, they still have more of these contaminants. It's not just that they're fatter. I should talk a little about the benefits of the Omega-3 fatty acids. Omega-3 fatty acids are a special kind of fat that's known as the good fat. There is very clear evidence the Omega-3 fatty acids help reduce the incidence of heart disease and there's building evidence that they may have beneficial effects against other diseases as well. So this is one of the reasons that many organizations, for example the American Heart Association recommends eating fish one or two meals per week. Well, no one denies that the Omega-3 fatty acids are heart healthy. It's also clear that these contaminants are heart damaging.

The PCBs and the dioxins cause the liver to make more cholesterol, and more lipids. People who are exposed to these compounds have higher circulating lipid levels, in general. We know that the biggest risk factor for heart attack is the level of cholesterol in serum lipids. It's interesting to compare these results with the recent studies on methylmercury. Methylmercury also accumulates in fish. Methylmercury also causes increases in susceptibility to heart disease. In a study published last November, it was demonstrated that men that ate a lot of ocean fish, which had high levels of methylmercury, actually suffered more heart attacks than men that didn't eat fish.

Now when they looked carefully, they could demonstrate the beneficial effect of the Omega-3 fatty acids. But this was counteracted and over-balanced by the harmful effects of the methylmercury. Now, there's another consideration with regard to the Omega-3 fatty acids. In recent studies, comparing people that had one fish meal a week or one fish meal a month as compared to people that didn't eat fish, it was found that clearly there were no added benefits beyond one fish meal a week. In other words, eating salmon four days a week is going to help you prevent heart disease. In fact, the health hazards from the contaminants will greatly overshadow the beneficial effects of the Omega-3 fatty acids. These studies looked at consumption of all seafood, all kinds of fish, plus shellfish in calculating the one meal per week. Therefore, while the non-fatty fish don't have as high Omega-3 fatty acids, they all have some. There are also other sources of Omega-3 fatty acids. Certain oils, certain beans -pinto beans, soybeans - all have Omega-3 fatty acids. So the question of the Omega-3 fatty acids as a health benefit does not constitute a reason to advocate high levels of consumption of farmed salmon or any other fish for that matter.

Can you compare FDA and EPA standards?

Well it's true that none of these salmon exceed the FDA standard of two parts per million for PCBs. However, that standard is not a health-based standard. It's not the FDA's fault because it's actually Congress that has mandated the FDA to set levels that regulate levels for interstate transport of foods. Those levels should reflect considerations of economic impact on industry and the considered heath effects. The two parts per million per PCBs standards was set a large number of years ago. It is not health protective and was never designed to be health protective. Now, the EPA standard is much more rigorous. For example, for PCBs, the EPA says it's safe to eat an unlimited number of fish if the PCB level is 0.05 parts per million. So what you see is a 400 fold lower value for safe consumption of fish.

What the EPA does in the standards that they developed for the Great Lakes is say, "All right, if fish have a contaminant at a level that is such you shouldn't eat them all the time as many as you want, then, at this level you should have not more than one meal per month." At this level, you should have not more than one meal per week. At this level, you shouldn't eat any at all. We think that standard, being based entirely on health effects outcomes is the appropriate one for the consumer to consider when they make decisions about whether or not they are going to eat farmed salmon.

Using the EPA standard, how often can people eat farmed salmon?

Unfortunately, it depends on where the salmon comes from and what its contaminant levels are. Of course, the consumer when they go into a supermarket has no idea. If the salmon you see in the supermarket says Atlantic salmon - it's a farmed salmon. But, one of the recommendations from our report is that it should be labeled as to what part of the world it comes from. We did find that salmon from the North Atlantic had significantly higher concentrations than salmon from the Pacific-both north and south.

However, we also did a systematic study of salmon filets purchased in 16 cities in Europe and North America. While most of the contaminated salmon purchased in supermarkets came from Europe, especially Frankfurt Germany, we found that salmon from Boston and from San Francisco were almost as high, whereas salmon purchased in Chicago and New Orleans were considerably lower. Now, the point is that in the salmon we happened to sample, it's almost certain that the salmon purchased in Chicago and New Orleans came from Chile, whereas those from Boston and San Francisco came from Europe. But the consumer doesn't know this-at least with present information. So I think the punch line is when you go to your supermarket you're not going to have any idea where that salmon comes from. And therefore, it's best to be cautious.

Since fishmeal is fed to poultry and swine as well as farmed fish, why the specific concern about farmed salmon, and not these other animals?

The levels of contaminants we found in the farmed salmon are much higher than are found in the other commonly consumed meats-beef, pork, chicken, eggs, and butter -all of the animal products. Now, that's not to say that there's no concern about the levels in these other products. I've just been on a National Academy of science panel looking at dioxin-like substances in the food supply where one of our major recommendations is we must stop the recycling of contaminated animal products into animal food. I think the worst situation is what we have with the farmed salmon. The degree to which that applies to other farmed fish is not clear at present, because there has not been this kind of study. It is true that fishmeal and fish oil are often used in the animal's foods for other kinds of animals. Although usually those foods contain fat from other kinds of animals as well. So, the problem goes beyond what we've found with the farmed salmon industry, but it's worse than any other previous demonstrated situation in this particular industry.

Why are dioxin and enzyme interrupters a health risk?

Well, dioxin's the clearest example because dioxin is rated by every national international agency as a proven human carcinogen. PCBs are rated as probable human carcinogens on the basis of evidence that they cause cancer in animals and consistent evidence of that conclusion that they cause cancer in people. Those compounds also suppress the immune system. These effects have been known for a long time, but I should say that if your immune system is suppressed, it makes you more vulnerable to every kind of infection. When you get a cold it's going to last longer. So those are serious issues.

In my judgment, the most dangerous things are more difficult to quantify, and we've had enormous progress in the last few years in understanding what they are. Perhaps, reflecting my own background in neuroscience, I think the most dangerous thing is the exposure to these compounds before birth. They cause a reduction in IQ of a child, a shortened attention span, a greater difficulty in dealing with frustrations, so there's more hostility-symptoms of ADHD that sort of thing in children. In addition, exposure before birth, in the early years of life, disrupts the endocrine systems.

This is particularly well demonstrated for the thyroid hormonal system which regulates our metabolism and the sex hormones system. Dioxins are anti-estrogenic, which means they tend to masculinize little girls. PCBs are dominantly estrogenic, which means they tend to feminize little boys. It's been well demonstrated that the cancers of the reproductive systems that occur at older than infancy are related to these alterations of the sex hormones. The relative balance of male and female sex hormones determines all of our sexual responses, physiology, and emotions.

These compounds mess that up. They are associated with decreased fertility. Especially in men, decreased sperm counts in adult men. They are associated with increased birth defects of the reproductive tract. There are increased incidents of undescended testicles or hypospadias, which is a birth defect in which the urethra doesn't empty at the end of the penis as it does in a normal person. So, they can alter both the cognitive intellectual function and reproductive function for the duration of a persons' life as a result of exposure before birth.

Now, one of the major recommendations of our National Academy report was that we try to have the public understand better the vulnerability of little girls. These compounds are persistent, by which we mean they stay in the human body for many years. For PCBs and dioxins, it takes about 10 years before you get rid of half of what you ate in that farmed salmon meal for dinner last night. That means if a 10-year-old girl is exposed to these compounds whether from eating salmon or other sources, if she gets pregnant and has a child at age 20, she's going to have half of those contaminants in her body. The child will get them when the child is growing in her body. If she breast feeds, breast milk is the only way in which humans excrete body fat. That contaminated body fat goes into the infant. Now there are lots of benefits of breast-feeding, but this is the negative. And that child is vulnerable to reduced IQ that will last for life, suppressed immune system, more vulnerability to infection, increased risks of cancer, increased risks of birth defects, and increased risk of having their reproductive sexual life altered by these prenatal exposures. It is a very, very frightening situation.

Anything we might want to add?

No, I think you've covered it very well. It's more important to get the punch line out than to go on forever. The punch line is that this is very dangerous stuff. What's so amazing to me is that the message just hasn't gotten to people. Partly it's because of organizations like the American Heart Association. It's almost that saying eating fish can be dangerous to your health is as bad as saying you shouldn't breast feed your child. It's interesting because I've gotten involved in just the last few weeks in a major debate on whether or not there are reasons to consider not breast-feeding, and also changing this message that fish consumption is always healthy with the International Joint Commission on issues around the Great Lakes focused primarily around mercury. But the issues are the same, though the distribution is somewhat different.

Could you comment on how we've polluted up the oceans?

Well, another important conclusion from this study is that we have fouled our nest. That even the oceans now, are sufficiently contaminated, that if we take the fish that nobody wants to eat, grind them up, concentrate them and feed them in large amounts to fish in a cage, those fish in a cage end up with contaminant levels that are dangerous to our health. Now, most people think the ocean is still an unlimited resource and that it's clean and will remain clean. But we have our contaminated rivers, one of which is right out here that flows right into the ocean. It carries with it contaminated sediments and water that contains low concentration of contaminants. Since that's happening from rivers all around the world, we now are in the situation where even concentrated meal from ocean fish is dangerous.

What about uncontaminated fish?

Well eating fish that are not contaminated is very healthy. Eating fish that are contaminated can be very dangerous. And for most of us there is some middle ground. Since all of them are contaminated to some degree, it's important that the consumer understand which are more contaminated, which are less. In general, small fish that eat plants are much healthier than big fish that eat medium size fish, because contaminants get bio-concentrated. So the tuna, the swordfish, the shark all have high levels of mercury. They are not farmed and they don't have particularly high levels of the organochlorines. The farmed fish that are fed contaminated fishmeal are going to accumulate that fishmeal. It's going to go into their bodies and when we eat them, we are going to bring those contaminants into our bodies. That is very dangerous.