Print
Add To FavouritesResearch -> Environmental Considerations
Environmental Considerations
Please click a topic to expand
- Lab tested, fish oil supplements pure and likely safer than eating fish
- Safety of fish oil supplements, negligible to nondetectable levels of mercury
- Mercury attenuates the benefits of fish oils, best avoided
- BBC News - Pollutants link to diabetes risk
- Environmental report on health risks associated with farm raised salmon
- Moms and Mercury - Nutrients in fish vital for infant cognitive development: moms need the nutrients without the mercury
- Exposure to Polychlorinated Biphenyls (PCBs) in moms impacts sex ratio of offspring
- Benefit-risk analysis suggests individuals cannot consume recommended EPA & DHA levels from diet alone, and of particular concern among pregnant and children
- News - Fish oil fights the effect of smog on the heart
- News - Women living in coastal areas are found to have higher mercury levels
- Useful link to info on Mercury and seafood
Melanson SF, et al. Measurement of organochlorines in commercial over-the-counter fish oil preparations: implications for dietary and therapeutic recommendations for omega-3 fatty acids. Arch Path Lab Med, 2005;129(1): 74-77.
CONTEXT: The consumption of fish high in omega-3 fatty acids is advocated by the American Heart Association to decrease the risk of coronary artery disease.
However, fish contain environmental toxins such as mercury, polychlorinated biphenyls, and organochlorine pesticides, which may negate the beneficial cardiovascular effects of fish meals. Toxin levels vary depending on both the fish source and the specific toxin, and neither farm-raised nor wild fish are toxin free.
Fish oil supplements also prevent the progression of coronary artery disease and reduce cardiovascular mortality. However, only sparse data exist on the level of toxins in fish oil. In a previous study we showed that the amount of mercury in 5 over-the-counter brands of fish oil was negligible.
OBJECTIVE: To determine the concentrations of polychlorinated biphenyls and other organochlorines in 5 over-the-counter preparations of fish oil.
DESIGN: The contents of 5 commercial fish oil brands were sent for organochlorine analysis.
RESULTS: The levels of polychlorinated biphenyls and organochlorines were all below the detectable limit.
CONCLUSIONS: Fish oil supplements are more healthful than the consumption of fish high in organochlorines.
Fish oils provide the benefits of omega-3 fatty acids without the risk of toxicity.
In addition, fish oil supplements have been helpful in a variety of diseases, including bipolar disorder and depression.
Foran SE, Flood JG, Lewandrowski KB. Measurement of mercury levels in concentrated over-the-counter fish oil preparations: is fish oil healthier than fish? Arch Pathol Lab Med, 2003; 127(12):1603-1605.
CONTEXT: Fish consumption has been associated with a decreased risk of coronary artery disease. Recent studies have illustrated that the high mercury content in cold-water fish may negate the cardiovascular benefits of fish meals. Fish oils have similar antiatherogenic properties to fish, and similar studies should be performed to determine the level of mercury in fish oils.
OBJECTIVE: To determine the concentration of mercury in 5 over-the-counter brands of fish oil.
RESULTS: The levels of mercury in the 5 different brands of fish oil ranged from nondetectable (<6 microg/L) to negligible (10-12 microg/L). The mercury content of fish oil was similar to the basal concentration normally found in human blood.
CONCLUSIONS: Fish are rich in omega-3 fatty acids, and their consumption is recommended to decrease the risk of coronary artery disease. However, fish such as swordfish and shark are also a source of exposure to the heavy metal toxin, mercury. The fish oil brands examined in this manuscript have negligible amounts of mercury and may provide a safer alternative to fish consumption.
Virtanen J, Voutilainen S. Mercury, Fish Oils, and Risk of Acute Coronary Events and Cardiovascular Disease, Coronary Heart Disease, and All-Cause Mortality in Men in Eastern Finland. Arteriosclerosis, Thrombosis, and Vascular Biology 2005;25:228.
Objective Mercury has been suggested to have negative effects on cardiovascular health. We investigated the effects of high mercury content in hair on the risk of acute coronary events and cardiovascular and all-cause mortality in men from eastern Finland.
Methods and Results The population-based prospective Kuopio Ischaemic Heart Disease Risk Factor Study (KIHD) cohort of 1871 Finnish men aged 42 to 60 years and free of previous coronary heart disease (CHD) or stroke at baseline was used. During an average follow-up time of 13.9 years, 282 acute coronary events and 132 cardiovascular disease (CVD), 91 CHD, and 525 all-cause deaths occurred. Men in the highest third of hair mercury content (>2.03 g/g) had an adjusted 1.60-fold (95% CI, 1.24 to 2.06) risk of acute coronary event, 1.68-fold (95% CI, 1.15 to 2.44) risk of CVD, 1.56-fold (95% CI, 0.99 to 2.46) risk of CHD, and 1.38-fold (95% CI, 1.15 to 1.66) risk of any death compared with men in the lower two thirds. High mercury content in hair also attenuated the protective effects of high-serum docosahexaenoic acid plus docosapentaenoic acid concentration.
Conclusions: High content of mercury in hair may be a risk factor for acute coronary events and CVD, CHD, and all-cause mortality in middle-aged eastern Finnish men. Mercury may also attenuate the protective effects of fish on cardiovascular health.
Mercury may increase the risk of cardiovascular diseases. In this study, high mercury content in hair increased the risk of cardiovascular morbidity and mortality in middle-aged Finnish men and attenuated the beneficial effects of fish oils on cardiovascular health. Regular consumption of fish with high mercury content should be avoided.
Exposure to high levels of a class of environmental pollutants may increase the risk of developing type 2 diabetes, research suggests.
A team from the University of Lund in Sweden found people exposed to high levels of persistent organochlorine pollutants (POPs) seemed more at risk.
POPs are most likely to come from eating fatty fish such as salmon. The study, of 196 fishermen and their wives, is published in the journal Environmental Health.
POPs are a family of toxic chemicals that includes polychlorinated biphenyls (PCBs) and the insecticide DDT. They are by-products of industrial and agricultural processes and are widespread in the environment.
The Lund team analysed blood samples from the volunteers for levels of a POP residue called CB-153, and DDE, the main by-product of DDT.
Significantly higher levels of both chemicals were found in the blood of the 6% of men and 5% of women who had type 2 diabetes.
Previous research has suggested that toxic chemicals like POPs may decrease the ability of the body's cells to take up glucose. Another theory is that the chemicals may trigger complex interactions which disrupt the body's ability to break down fats.
Unusual circumstances
Researcher Dr Lars Hagmar told the BBC News website that people should not worry about eating oily fish. He said the fishermen and their wives in the study were exposed to exceptionally high levels of pollutants.
The Baltic coast, where they ply their trade, had been heavily polluted with POPs from industry, he said. The water was also shallow and cold, meaning that pollutants took a long time to start to degrade.
The Baltic Sea was also surrounded by land with relatively little circulation of its waters, so pollutants were not as readily dispersed as they were in other bodies of water.
Amanda Eden, a care advisor at Diabetes UK, said: "While this study looks interesting, more extensive research is required before we can draw any firm conclusions of a link between these toxins and Type 2 diabetes.
"What we do know is that, a healthy, balanced diet and regular physical activity can help reduce the risk of developing Type 2 diabetes.
"We also recommend that people aim to eat oily fish such as salmon or mackerel twice a week as part of a healthy, balanced diet."
Foran J, Carpenter D, et al. Risk-Based Consumption Advice for Farmed Atlantic and Wild Pacific Salmon Contaminated with Dioxins and Dioxin-like Compounds. Environ Health Perspect. 2005;113(5):552-557
We reported recently that several organic contaminants occurred at elevated concentrations in farmed Atlantic salmon compared with concentrations of the same contaminants in wild Pacific salmon [Hites et al. Science 303: 226-229 (2004)].
We also found that polychlorinated biphenyls (PCBs), toxaphene, dieldrin, dioxins, and polybrominated diphenyl ethers occurred at higher concentrations in European farm-raised salmon than in farmed salmon from North and South America.
Health risks (based on a quantitative cancer risk assessment) associated with consumption of farmed salmon contaminated with PCBs, toxaphene, and dieldrin were higher than risks associated with exposure to the same contaminants in wild salmon.
Here we present information on cancer and noncancer health risks of exposure to dioxins in farmed and wild salmon. The analysis is based on a tolerable intake level for dioxin-like compounds established by the World Health Organization and on risk estimates for human exposure to dioxins developed by the U.S. Environmental Protection Agency.
Consumption of farmed salmon at relatively low frequencies results in elevated exposure to dioxins and dioxin-like compounds with commensurate elevation in estimates of health risk.
Moms and Mercury by Ernie Hood. Fine-Tuning Fish Consumption During Pregnancy. Environmental Health Perspectives, 2005;113:1376-1380.
EHP is a monthly journal of peer-reviewed research and news on the impact of the environment on human health.
Due to ongoing concerns that high mercury intake via fish can cause adverse neurologic effects in the developing fetus, the U.S. Food and Drug Administration now recommends that expectant mothers should limit their consumption of fish to two or fewer meals per week. But pregnant women shouldn't throw the baby out with the bathwater.
A new study by a group of Harvard researchers suggests that this advice, which could result in many pregnant women eliminating fish from their diets altogether, may be denying some babies substantial neurocognitive benefits gained from important nutrients found in fish, such as n-3 polyunsaturated fatty acids.
The scientists sought to determine whether fish consumption during pregnancy is harmful or beneficial to fetal brain development. To do this, they examined associations of maternal fish consumption during pregnancy, maternal hair mercury levels (a sensitive marker of organic mercury body burden) at delivery, and infant cognition at age 6 months. Study subjects were 135 mother-infant pairs who participated in Project Viva, a prospective pregnancy and child health cohort study in eastern Massachusetts.
The mothers completed questionnaires about fish consumption during their second trimester. That period of time was used to best coordinate temporally with the mercury exposure reflected in maternal hair samples, which were taken at delivery. The questions concerned how much and what categories of fish (canned tuna, dark meat, light meat, shellfish) the women ate.
Mothers consumed an average of 1.2 servings of combined fish categories per week. Their mean hair mercury level was 0.55 part per million (ppm), with 10% of the samples higher than 1.2 ppm, the current U.S. reference dose. Fish consumption was directly correlated with hair mercury levels.
Infant cognition was assessed using a test called visual recognition memory (VRM). In the VRM test, which has been shown to correlate with later IQ, the child is first shown two identical photographs of an infant's face, side by side, at a standardized distance. Then, one of the photos is replaced with a photo of another infant's face. By tracking the percentage of time the baby looks at each photo, a novelty preference score is derived, reflecting the infant's ability to encode a stimulus into memory, to recognize that stimulus, and to look preferentially at a novel stimulus.
Mean VRM score among the children was 59.8, with a range of 10.9-92.5. After accounting for characteristics such as maternal age and education level, higher fish intake was found to be associated with higher infant cognition, especially after adjusting for mercury levels, which had a dose-dependent negative impact on the infants' cognition. For each additional weekly serving of fish, the infants' VRM score was 4.0 points higher. Conversely, the researchers found that an increase of 1 ppm in hair mercury was associated with a decrement in VRM score of 7.5 points.
The babies with the highest cognition scores were from mothers who had eaten more than two weekly fish servings but had mercury levels of 1.2 ppm or less.
Although the results may seem contradictory, the authors suggest that the most cognitive benefit is derived by mothers eating fish types with the combination of relatively little mercury and high amounts of beneficial nutrients. However, since the study assessed maternal fish consumption of four broad categories, there is no information presented on associations with specific types of fish. The researchers say that future studies could incorporate more detailed dietary information to help pregnant women make informed decisions about which fish meals are better or worse for their children's cognition.
Ultimately, the message behind these findings is that pregnant women should continue to eat fish, but should try to choose varieties known to be low in mercury and high in nutrients, such as canned light tuna and sardines. Finding the most appropriate balance between risk and benefit may be challenging in this situation, but given the strong associations found in the current study, making the right decisions about which fish to eat during pregnancy, and how often, may be even more important than previously suspected.
MG Weisskopf, HA Anderson, LP Hanrahan, and Great Lakes Consortium. Decreased sex ratio following maternal exposure to polychlorinated biphenyls from contaminated Great Lakes sport-caught fish: a retrospective cohort study. Environ Health,2003;2(1):
Background
Fish from the Great Lakes are contaminated with polychlorinated biphenyls, which have been found to have several adverse reproductive effects. Several environmental contaminants have been found to alter the sex ratio of offspring at birth, but the evidence of such an effect of polychlorinated biphenyls has been inconsistent.
Methods
We examined parental serum polychlorinated biphenyl concentration in relation to the sex ratio of 173 children of mothers and 208 children of fathers from the Great Lakes region of the United States between 1970 and 1995. We calculated odds ratios for a male child using logistic regression and generalized estimating equations with adjustment for the year of birth of the child, maternal and paternal age, the mother's parity at the child's birth, and whether the child had an older brother.
Results
The adjusted odds ratio for having a male child among mothers in the highest quintile of serum polychlorinated biphenyl concentration was 0.18 (95% CI: 0.06-0.59) compared to mothers in the lowest quintile. Treating exposure as a continuous variable, the adjusted odds ratio for having a male child was 0.54 per unit increase in the natural log of maternal serum polychlorinated biphenyl concentration (95% CI: 0.33-0.89). There was little evidence of an association with paternal exposure. We found no association between either maternal or paternal serum dichlorodiphenyl-dichloroethene concentration and the sex ratio.
Conclusions
These findings suggest that maternal exposure to polychlorinated biphenyls may decrease the sex ratio of offspring. These data add to the growing body of evidence that exposure to particular chemicals can alter the sex ratio at birth.
Foran JA, Good DH, et al. Quantitative Analysis of the Benefits and Risks of Consuming Farmed and Wild Salmon. J. Nutr., 2005;135:2639-2643.
Contaminants in farmed Atlantic and wild Pacific salmon raise important questions about the competing health benefits and risks of fish consumption.
A benefit-risk analysis was conducted to compare quantitatively the cancer and noncancer risks of exposure to organic contaminants in salmon with the (n-3) fatty acid?associated health benefits of salmon consumption.
Recommended levels of (n-3) fatty acid intake, as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), may be achieved by consuming farmed or wild salmon while maintaining an acceptable level of noncarcinogenic risk. However, the recommended level of EPA+DHA intake cannot be achieved solely from farmed or wild salmon while maintaining an acceptable level of carcinogenic risk.
Although the benefit-risk ratio for carcinogens and noncarcinogens is significantly greater for wild Pacific salmon than for farmed Atlantic salmon as a group, the ratio for some subgroups of farmed salmon is on par with the ratio for wild salmon.
This analysis suggests that risk of exposure to contaminants in farmed and wild salmon is partially offset by the fatty acid?associated health benefits.
However, young children, women of child-bearing age, pregnant women, and nursing mothers not at significant risk for sudden cardiac death associated with CHD but concerned with health impairments such as reduction in IQ and other cognitive and behavioral effects, can minimize contaminant exposure by choosing the least contaminated wild salmon or by selecting other sources of (n-3) fatty acids.
By Kathleen Doheny, HealthDay Reporter
Daily supplements of fatty acid-rich fish oil may counteract the effects of air pollution on the heart, researchers report.
"The cardiac responses to air pollutants were dramatically reduced in those on fatty acids," said Dr. Fernando Holguin, an assistant professor of medicine at Emory University School of Medicine. He presented the research this week at the American Thoracic Society's annual meeting in San Diego.
Holguin's team tracked the cardiac health of 50 elderly people, all nursing home residents averaging 70 years of age and living in smog-plagued Mexico City.
Each resident received a one-gram oil capsule twice a day (once in the morning and again in the evening) containing omega-3 fatty acids. Half of the group received fish oil capsules and the other half soy oil capsules.
The researchers took ongoing measurements of each participant's cardiac function, focusing specifically on their heart rate variability. Heart-rate variability refers to the heart rate alterations from beat to beat.
"Exposure to the particles of air pollution reduces heart rate variability, and taking the omega-3 fatty acids increased it," Holguin explained. "Increased heart rate variability reduces heart disease risk."
The fish oil was much better at keeping heart rate healthy than was the soy oil, the Emory team found. "Those on soy oil had just marginal protection," Holguin said, while "those on fish oil had a complete abolishment of the effect of the [smog] particles on the heart."
Another expert, Dr. Zi-Jian Xu, a staff cardiologist at Santa Monica-UCLA Medical Center and an assistant clinical professor of medicine at the David Geffen School of Medicine, UCLA, said he is not surprised by the results. "Fish oil has been found to reduce cardiovascular events, mainly heart attack and stroke," he said. "It has also been shown to modestly reduce the risk of another heart attack. The theory is that omega-3 fatty acids can improve cardiovascular health."
The new finding is also consistent with previous research, Xu added. Holguin advises that people follow the advice of the American Heart Association (AHA) with regards to their daily intake of omega-3 fatty acids.
The AHA currently recommends that individuals with documented heart disease eat about one gram of omega-3 fatty acids a day, preferably from fatty fish.
Source: http://healthinfo.cedars-sinai.edu/healthnews/healthday/050526HD525935.htm
Women in Coastal Areas Are Found to Have Higher Mercury Levels
By Juliet Eilperin, Washington Post Staff Writer
Women in coastal communities have twice as much mercury in their blood as those living inland, according to an analysis by an Environmental Protection Agency scientist.
The preliminary findings, based on a survey of 3,600 women conducted by the Centers for Disease Control and Prevention between 1999 and 2002, provide fresh evidence of the link between fish consumption and concentrations of methylmercury, a neurotoxin that causes developmental problems in young children.
The study focused on the 10 percent of women with the highest mercury levels, and in that group, it found that inland residents had an average level of 2.4 parts per billion, compared with 5.9 parts per billion for coastal residents. EPA guidelines hold that mercury levels higher than 3.5 parts per billion pose a possible health threat.
Mercury, spewed into the air in emissions from power plants and other sources, ends up in water and accumulates in predator fish such as tuna and swordfish. In pregnant women with high levels, methylmercury crosses the placenta and can affect the developing brain of the fetus.
"What's evident in these data is there's a real difference between the coastal and non-coastal" women, said Kathryn Mahaffey, who conducted the analysis as director of the EPA's division of exposure assessment, coordination and policy. "The message is people need to eat a variety of foods and, when choosing fish species, they need to choose more than one type of fish."
The EPA recommends that women of childbearing age limit their albacore tuna consumption to six ounces, or an average meal, a week. The agency suggests that women eat as much as 12 ounces a week of fish or shellfish that are lower in mercury, such as salmon, shrimp and trout.
Mahaffey said agency scientists did not obtain a detailed diet breakdown from the women, but they assumed that those living in coastal areas ate more fish. A study published this year found that French women living on the coast consume three times as much fish as those living inland.
American women living on the Atlantic Coast had much higher mercury levels than those living on the Pacific or Gulf coasts. Atlantic Coast residents had average levels of 7.7 parts per billion, while women on the Pacific had levels of 4.7 and women on the Gulf Coast had 3.2 parts per billion.
Mahaffey said she could not account for the discrepancy, adding, "Fish are just not all the same."
The study, obtained by The Washington Post from the nonprofit Natural Resources News Service, also indicated that wealthier women were more likely than poor women to have elevated mercury levels. Women earning less than $20,000 annually had an average level of 2.8 parts per billion, while women earning more than $20,000 had 3.9 parts per billion.
Environmentalists said the survey -- along with another this week in the journal Environmental Health Perspectives that showed Asian, Pacific Islander and Native American women have higher mercury levels than women from other backgrounds -- should remind Americans of the health dangers contaminated fish can pose.
"It reaffirms there's a strong connection to ocean fish, but that's not to say non-coastal residents are safe," said Jackie Savitz, who directs the seafood contamination campaign at Oceana, an advocacy group. "Alarms should really be sounded for everyone."
Oceana has lobbied grocery store chains -- including Safeway, Wal-Mart and Whole Foods -- to post signs identifying which fish are high in mercury.
Source: washingtonpost.com
This web site is a project of the Program on Agriculture and Animal Health Policy (PAAHP) of the Center for Food, Nutrition, and Agriculture Policy (CFNAP) at the University of Maryland.
The project is intended to help scientists, the public, the media and policy makers understand the range of published studies and analyses on the important issue of mercury and seafood.
Source: http://www.realmercuryfacts.org/
