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More Iodine or Less Perchlorate?
It is thought that perchlorate blocks the uptake of iodine into the thyroid, eventually resulting in the decreased production of the thyroid hormones thyroxine and triiodothyronine. However, according to a new scientific review of perchlorate, reducing the risk of mental deficits in children whose mothers are exposed to the chemical may be achieved most efficiently by correcting the iodine deficiency that occurs in roughly a third of U.S. women of child-bearing age—not by reducing perchlorate intake. The review is a first for the U.S. Environmental Protection Agency (EPA) Office of Inspector General (OIG), which primarily conducts audits, evaluations, and investigations of the EPA and its contractors to promote economy and efficiency, and to prevent and detect fraud, waste, and abuse. But rather than resolving controversy over the risk characterisation of perchlorate, the review appears instead to be further fuelling it. In comments offered in response to the review, the Environmental Working Group wrote that the OIG had used the review to justify their endorsement of the Bush Administration’s failure to set a drinking water standard perchlorate, which pollutes the drinking water of an estimated 20–40 million people nationwide. But Purnendu Dasgupta, an analytical chemist at the University of Texas, Arlington, applauds the OIG for stepping in to address a major public health gap. “The continued brouhaha about perchlorate alone, whether by activists or protectionists, merely acts as a smokescreen,” he says. “We have urgent problems about iodine nutrition; the preoccupation with perchlorate alone is obscuring the fact that we are gambling with the intellectual future of the next generation at our peril.” Perchlorate is thought to affect thyroid function by blocking uptake of iodine, an essential component of thyroid hormones, which orchestrate brain development. Other chemicals—in particular, thiocyanate (found in tobacco smoke and cruciferous vegetables) and nitrate (found in leafy vegetables, processed meats, and some contaminated water supplies)—act in a similar way. In addition, too little iodide has the same effect. The OIG considered all four of these factors in its cumulative risk assessment, a type of assessment that looks at the public health risk arising from multiple, combined stressors. By attempting a more holistic cumulative assessment, OIG says it is at the vanguard of governmental agencies in following recommendations from several recent governmental advisory committees.
House and Senate draft versions of chemical regulation reform bills also call for cumulative risk assessments. Risk assessment specialists generally applaud this innovative aspect of the OIG effort. But many comments on the report referred to the lack of peer review, failure to consider major studies, failure to specifically consider the risk of perchlorate exposure to infants, and an excessive reliance on one in vitro study that estimated the relative potencies of the different thyroid stressors in terms of their ability to block iodine uptake. The OIG hired consultancy ICF International to conduct a technical review of the assessment. ICF International broadly endorsed the OIG’s cumulative risk assessment approach, but recommended the use of more recent peer-reviewed human studies, in particular a 2006 study that found a statistically significant association between changes in thyroid function to levels of perchlorate exposure roughly an order of magnitude lower than those in previous studies of people exposed to perchlorate. The Environmental Working Group contends ICF International had a potential conflict of interest because the firm has consulted for federal agencies, military contractors, and other entities responsible for perchlorate pollution in drinking water supplies, all of whom “have vigorously opposed strong public health standards for perchlorate.” The Massachusetts Department of Environmental Protection raised similar concerns. However, the OIG contends ICF International was selected as the best qualified bidder under federal guidelines. Other questions revolve around data suggesting perchlorate may have additional mechanisms of action beyond its ability to inhibit iodine uptake. “Although the OIG study is informative with respect to cumulative impacts at the level of thyroidal iodine uptake, the potential existence of additional mechanisms of action should temper conclusions regarding appropriate perchlorate exposure limits, especially where the iodine uptake inhibition estimates are derived from an in vitro model that does not reflect the complexity of in vivo thyroid function, effects, and responses,” says toxicologist C. Mark Smith of the Massachusetts Department of Environmental Protection. Adam Finkel, a member of the National Research Council committee that evaluated EPA risk assessment protocols, notes moreover that cumulative risk assessments such as this could end up yielding questionable policy. “Advocates for holistic risk assessments assumed the point to be that you can make a stronger case for reducing pollutant X if you see it in context of all the other things also adding to the burden of disease Y—but this report turns that logic on its head and says essentially that when you see the whole picture, you see a reason to ignore the pollutant and work on the other things,” he explains.
The conclusions of the review disagrees with risk assessments conducted by states such as California and Massachusetts, which have adopted health recommendations more stringent than the current EPA reference dose for perchlorate of 0.0007 mg/kg/day (total intake from both water and food). “Although improving iodine nutrition is an important public health issue itself, it is an incomplete response to perchlorate drinking water contamination,” Smith says. “Infants are the population of greatest concern identified in the Massachusetts risk assessment, but the OIG assessment doesn’t adequately address their demonstrated potential for significant perchlorate exposure and risk.” “It’s great that this cumulative assessment looks more broadly and seeks to consider possible risk management solutions early in the assessment process,” says Finkel. “But while adding iodide may be the most efficient solution, that is not for the risk assessor to prejudge—we need a document that lays out the costs and benefits of alternative approaches, not one that trivializes the environmental risk because there may be a ‘supply side’ way of sidestepping it.” Jonathan Levy, who also was a member of the panel that evaluated EPA risk assessment protocols, agrees. “Our NAS committee recommendations would argue that the presence of multiple stressors would imply that health effects would be anticipated at low dose of perchlorate,” he says. “The fact that other stressors have greater effects is an interesting observation, but we explicitly stated that this should not be the primary output of cumulative risk assessment.”
Environmental Health Perspectives, July 2010 http://ehponline.org
Farm, food service jobs tied to heart disease risk
A new study has revealed that Americans working in certain industries, including transportation, food service and farming, may have a relatively high rate of risk factors for heart disease, diabetes and stroke, a new study finds. At the other end of the spectrum, researchers found, health professionals, scientists and artists are among those with the lowest rates of so-called metabolic syndrome. Metabolic syndrome refers to a collection of risk factors for diabetes, heart disease and stroke -- including abdominal obesity, high blood pressure, high blood sugar, low levels of “good” HDL cholesterol and high triglycerides (another type of blood fat).
The syndrome is typically diagnosed when a person has three or more of those conditions, and the National Health and Nutrition Examination Survey, a major study, found that it can double the risk of heart attack and stroke. During the new study, the researchers observed that among a nationally representative sample of U.S. adults, workers in the farm industry and food service (other than waiters and waitresses) had the highest rates of metabolic syndrome -- at around 30 percent. That compares to an overall U.S. risk of about 22 percent, according to the National Health and Nutrition Examination Survey. Meanwhile, the risk factors were seen in roughly one-quarter of Americans in the transportation industry (truck drivers and other workers), construction and non-professional health services (excluding people such as doctors and nurses). At the other end of the heart-risk spectrum were “writers, artists, entertainers and athletes” and the category that included scientists, engineers and architects, where the rates of metabolic syndrome were 8 percent to 9 percent. Doctors, nurses and other health professionals, meanwhile, had a rate of 12 percent. The findings from the study were published recently in the journal Diabetes Care.
In most cases, the job-related differences in metabolic syndrome appeared to be explained by differences in other associated factors -- including rates of obesity and smoking, exercise habits and race. The exception was the transportation industry, where the work itself remained linked to an increased risk of metabolic syndrome even with the other factors taken into account. The reasons for that finding are not clear, according to the researchers, led by Dr. Evelyn P. Davila of the University of Miami. However, they note, the finding is in line with past studies that have found relatively higher rates of heart disease and stroke among truck drivers and other transportation workers compared with other lines of work. It’s possible, Davila and her colleagues write, that factors not measured in this study -- such as irregular work schedules and poorer sleep habits, or job stress -- might help explain the link between transportation work and metabolic syndrome. The findings, according to the researchers, do not prove that any given occupation increases or decreases the risk of metabolic syndrome. However, they do suggest that people in certain job fields need to be especially aware of ways to control their risk factors for heart disease and diabetes. That includes watching their diets and getting regular exercise, not smoking and, if necessary, taking medication to control their blood pressure and cholesterol. Furthermore, according to the researchers, certain workplaces should be targeted for health-promotion programs that raise awareness of metabolic syndrome and how to help prevent it.
Reuters Health,15 July 2010 http://www.reuters.com/news/health
EPA Exposure Assessment: PBDEs
A new EPA exposure assessment has demonstrated that U.S. exposure to polybrominated diphenyl ethers (PBDEs) occurs primarily through house dust, unlike other persistent organic pollutants, which typically are encountered in food. In addition, weight-specific intake rates are higher for U.S. children, especially infants, than for adults. The EPA is planning to issue new rules later this year for the manufacture and import of products containing two specific PBDEs. PBDE flame retardants, some of which have already been phased out of commerce, are used in applications including furniture and electronics.
Environmental Health Perspectives, July 2010 http://ehponline.org
Less Salt for Everybody
Researchers Dieter Klaus and colleagues have found that by restricting the amount of sodium chloride in food can lower the risk of cardiovascular morbidities. This findings was published in the current issue of Deutsches Ärzteblatt International. People whose intake of dietary sodium chloride is in excess of 6 g per day increase their risk of cardiovascular morbidities and hypertension. This is particularly notable in view of the fact that in the Western industrialised nations, one in two deaths is due to a cardiovascular disorder and the average intake of sodium chloride is in the range of 8 to 12 g/d. Salt restriction may help not only to prevent cardiovascular morbidities but may also counteract other lifestyle diseases such as obesity and diabetes. As a preventive measure, the authors suggest reducing dietary salt intake population-wide. By successively lowering the NaCl content of industrially processed foods by 40% to 50%, people’s daily salt intake would be lowered to 5 to 6 g/d per head of population
Science Daily, 16 July 2010 http://www.sciencedaily.com
“Safer” Cigarettes Still Hazardous
Smoking tobacco- and nicotine-free cigarettes made of lettuce may be at least as hazardous as smoking conventional tobacco cigarettes, if not more so. In a study of the supposedly safer cigarettes, which were introduced in 1997, dose-dependent double-strand DNA breaks were seen after shorter durations of exposure to smoke compared with conventional cigarettes. Furthermore, the tobacco- and nicotine-free cigarettes delivered far higher doses of total particulate matter (“tar”).The researchers used phospho-specific antibodies to measure DNA damage response and their own laser scanning cytometry instrumentation, which they say should be a useful complement to other methods for assessing genotoxicity of cigarette smoke.
Environmental Health Perspectives, July 2010 http://ehponline.org
Low vitamin D increases risk of dementia in elderly
The findings from a new study have suggested that older people with low levels of vitamin D appear more likely to have problems with memory, learning and thinking, suggesting low vitamin D could give an early warning for dementia risk. The researchers from Britain, Italy and the United States studied 850 Italians aged 65 or older and found that those who were severely vitamin D deficient were 60 percent more likely to experience substantial general cognitive decline, and 31 percent more likely to experience problems with mental flexibility. “This is the first study to identify a clear link between low vitamin D levels and cognitive decline,” said David Llewellyn of the Peninsula Medical School at Britain’s Exeter University, who led the study. “We have now been able to demonstrate a connection between having low levels of vitamin D and going on to develop cognitive problems.” Since an estimated one billion people worldwide have insufficient levels of vitamin D, Llewellyn said the findings were “a cause for real concern.” Giving vitamin D supplements to older people to boost their levels could be “a highly promising therapeutic target for the prevention of dementia,” he said, particularly since supplements are cheap, safe and have already been shown to help prevent to reduce the risk of falls and fractures. Most vitamin D is made by the body as a natural by-product of the skin’s exposure to sunlight. In addition, it can be found in a few foods such as oily fish and is vital for health, as it helps cells absorb calcium and is key for bone strength. Some recent studies have also suggested vitamin D may protect against cancer, artery disease and tuberculosis.
In this study, Llewellyn’s team found that older people who were severely deficient in vitamin D -- defined as having blood levels of 25-hydroxyvitamin D of less than 25 nanomoles per litre -- were 60 percent more likely to have substantial cognitive decline were 1 percent more likely to show decline in a test measuring executive function than those with good vitamin D levels. The findings were published in the Archives of Internal Medicine journal. Dementia is a brain-wasting condition that affects around 35 million people worldwide. Its most common form is Alzheimer’s disease, in which patients gradually to lose their memory, their ability to navigate and understand the world around them and to look after themselves. Despite decades of research, doctors still have few effective weapons against it. Llewellyn’s team said they thought Vitamin D may help prevent the degeneration of brain tissue by having a role in formation of nervous tissue, maintaining levels of calcium in the body, or clearing of beta-amyloid, the substance that forms the brain plaques that are associated with Alzheimer’s disease. Experts estimated that in the United States and Europe, between 40 percent to 100 percent of older adults are deficient in vitamin D and the problem is aggravated in the elderly as they spend more time indoors and their skin becomes less efficient at producing vitamin D with age.
Reuters Health, 12 July 2010 http://www.reuters.com/news/health