~dGossip
~tChemicals and Noise - A Hazardous Combination
~w2009-11-05
It comes as no surprise to find out that most of the work-related hearing loss is caused by exposure to noise. In addition, genetics and age can contribute. What many people do not realise is that exposure to chemicals may pose a potential risk to hearing. In both animal experiments and human studies, researchers have found that certain chemical exposures may cause "ototoxic" effects (damage the hearing and balance functions of the ear). In general, the exposure concentrations that cause these effects are considered high. However, exposure to some of these chemicals and noise at the same time can significantly increase the risk of developing ototoxic effects.
What are ototoxins?
Ototoxins are chemicals that can damage hearing and can cause mild to severe hearing loss, tinnitus (ringing in the ears), or deafness. An ototoxin can be ingested, absorbed, or inhaled into the body. Once in the bloodstream, the ototoxin is circulated to the ear and absorbed by the auditory nerve, damaging the nerve and causing hearing loss. Furthermore, ototoxins can cause hearing loss by damaging the cochlear hair cells (as happens in hearing loss caused by noise).
Effects of chemical exposure on hearing
Ototoxic chemicals can cause hearing loss on their own, however when combined with noise exposure, the effects can be even more severe. Organic solvents are the most commonly identified chemicals, but others may also be involved (e.g. metals and chemical asphyxiants). The hearing frequencies affected by solvent exposure are different than those affected by noise. Research suggests that solvents may interact synergistically with noise. Even when noise and chemicals are at permissible exposure levels, the impact of a combined exposure can do more damage than a higher exposure to either hazard alone.
Some chemicals associated with hearing loss are:
- Benzene
- Carbon disulfide
- Carbon monoxide
- Ethylbenzene
- Hydrogen cyanide
- Lead
- Mercury
- n-Hexane
- Solvent mixtures
- Styrene
- Trichloroethylene
- Toluene
- Xylene
Organic solvents are widely used: in automotive and aviation fuels; in plastics industries; as thinners for paints, lacquers and dyes; in the manufacture of detergents, medicines, perfumes, fabric and paper coatings, printing inks, spray surface coatings; and in insect repellents. Activities where noise and chemical hazards can potentially combine include:boat building; construction; firefighting; fuelling vehicles and aircraft; furniture making; manufacturing of metal, leather and petroleum products; painting; printing; weapons firing.
Challenges
It may be difficult to determine the ototoxic effects of chemicals, particularly organic solvents, in exposed workers. Workers are usually exposed to a mixture of solvents with various compositions and concentrations, making it difficult to isolate exactly which chemical, and how much exposure to that chemical is causing damage. Also the industrial environments in which there tend to be exposures to both chemicals and high levels of noise make it difficult to differentiate the solvent effect from noise-induced hearing loss. Although there is no firm guidance on the lowest occupational exposure limits for solvents in relation to their effect on hearing, the current occupational exposure limits as well as hearing conservation programs for solvent-exposed workers may not be adequate.
How to protect workers
The first step in a hearing loss prevention program is to undertake a hazard assessment to determine if and what hazardous exposures exist in the workplace.Remove the source of hazardous exposures from the workplace (the most effective way to prevent hearing disorders from noise or chemical exposure, but may not be possible).Substitute ototoxins with less hazardous chemicals. Take steps to minimise potential ototoxin exposures through inhalation, ingestion, and/or skin absorption. Minimise exposure to these chemicals through process changes, ventilation, and/or skin or respiratory protection. Reduce noise levels through engineering or administrative controls. Wear hearing protection when exposed to noise, or when exposed to ototoxins - even when noise levels are below the threshold - to prevent the combined effects of noise and solvent exposure.
Start a hearing conservation program for workers at lower levels of noise exposure than is required by occupational health and safety legislation. Include workers exposed to chemicals in hearing conservation programs, whether or not they are exposed to noise. These programs should consider the possible combined effects of exposure to both solvents and noise.There is a growing awareness of the chemical hazards to hearing that will hopefully lead to reduced risk of work-related hearing loss.
Canadian Centre for Occupational Health & Safety Newsletter, October 2009
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~dGossip
~tEating more dairy fights fat
~w2009-11-05
A new study by researchers from Curtin University of Technology has shown that a higher intake of dairy products while on a reduced calorie diet can help fight obesity. Benefits include greater weight loss and significant improvements in the risk factors for cardiovascular disease and diabetes. During the study, which was part of her PhD research, Dr Wendy Chan She Ping Delfos, from Curtin’s School of Public Health, compared three serves of dairy with five serves of dairy within a reduced calorie diet prescribed to overweight participants over a 12-week weight loss trial. The results indicated that those participants consumed five serves of dairy as opposed to three serves of dairy hada higher mean levels of weight loss;higher mean levels of fat mass loss;greater drop of systolic blood pressure; andgreater total percentage abdominal fat loss. “Many people commonly believe that when trying to lose weight dairy products are key foods that they have to cut out of their diet as they are high in fat," Dr Chan She Ping Delfos said. “This study has shown that when trying to lose weight people can actually benefit by increasing the amount of dairy they consume beyond the normally recommended three daily serves as long as during the weight loss period total energy intake is less than their requirements. “Increasing dairy intake to five serves per day as part of a reduced calorie diet has never been studied before, and such diets containing high levels of protein, calcium and vitamin D, among other bioactive nutrients, can be an important part of a prudent weight loss or weight maintenance diet.” In addition, Dr Chan She Ping Delfos, who worked with Curtin’s Associate Professor Mario Soares on the project, examined the effect of resistance exercise in combination with a high dairy, reduced calorie diet. “Participants who had five serves of dairy and engaged in resistance exercise had similar health benefits to participants consuming five serves of dairy only,” she said. “However, the participants who engaged in resistance exercise did show significantly less muscle loss during the weight loss trial and had a higher fasting fat oxidation rate (burning of fat) during the trial. “The group of participants engaging in resistance exercise also had a lower percentage of total fat regain at a follow-up visit 12 weeks after the initial trial. “Based on these results, we can conclude that the addition of resistance exercise to a high-dairy, reduced calorie diet can be better for longer-term weight maintenance.” The dairy products consumed by the participants consisted of cheese, yoghurt and low fat milk. The study tailored the intake of carbohydrates, proteins, and fats in each volunteer and monitored the change in weight, body fat, glucose levels and other cardiovascular risk factors.
Science Alert, 21 October 2009
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~dGossip
~tDNA Method Identifies Unknown Viruses in Reclaimed Water
~w2009-11-05
A new study, recently published in the journal Environment Biology, by Karyna Rosario, a Ph.D. student at the University of South Florida's College of Marine Science, used a novel technique to identify a full-range of unknown viruses in treated reclaimed water from plants in Pinellas and Manatee counties. According to Rosario, none of the viruses are human pathogens, putting to rest the most serious of fears about humans using treated wastewater. However, the new research provides an important starting point for future research on viruses that survive the human body and are discharged into reclaimed water and how they might impact the environment.Rosario, conducted the study under the supervision of Professor Mya Breitbart, whose laboratory uses a technique for identifying previously unknown viruses based on their genetic material (DNA or RNA). The study – “Metagenomic Analysis of Viruses in Reclaimed Water” – describes the method developed by Breitbart’s lab. Samples containing a host of viruses are processed to extract the virus’ DNA. The DNA is sequenced and then compared to existing databases of known DNA genomes to identify the viruses. Although, the difficult part for the researchers is that with millions of types of viruses in existence, there are still many more viruses that have yet to be identified and mapped. The process used in Breitbart’s lab also helps to identify never-before-seen viruses. During the new study, Rosario compared samples collected from effluent at a reclaimed water plant; reclaimed water coming from a public sprinkler; reclaimed water used at a plant nursery and drinking water from a plant nursery. She found reclaimed water contained 1,000-fold more virus-like particles than potable water and that reclaimed water may play a role in the dissemination of highly stable viruses.
The viral community was dominated by viruses that infect bacteria, but viruses related to animal, plant, and insect pathogens were also identified. She concluded that further studies are required to determine the impacts of reclaimed water use on human and ecosystem health. Currently in Florida, reclaimed water is used for non-potable public water supply, crop irrigation, lawn watering, industrial uses and groundwater recharge. However, an increasingly serious drought has led to some new considerations for using reclaimed water as a potential source of drinking water. This summer, the Tampa City Council voted to ask residents in a 2010 ballot question to consider whether highly treated reclaimed water could be returned to the city’s drinking water supply.One of the biggest concerns about reclaimed water use is whether it carries and spreads pathogens, and until recently the microbiological content of reclaimed water was still largely unknown. Viruses are of particular concern because they include highly stable pathogens that can be resistant to standard wastewater treatment processes, Rosario explained, noting that for practical reasons, current quality control methods do not test the presence of pathogens directly and the spread of viral pathogens through reclaimed water remains a real possibility.In Tampa, where 55 million gallons of treated wastewater a day is discharged into TampaBay, the safety of reclaimed water also has become a large environmental concern.In the samples taken from the effluent and nursery irrigation systems ,viruses related to Rhinovirus – the cause of the human cold – were present, as well as Enterovirus, which is a large and diverse group of viruses which in some forms can cause human maladies, such as meningitis and foot and mouth disease. Similarities to cow, pig and monkey viruses also were identified in the samples.The value of knowing that viruses exist in treated wastewater is that scientists now have a baseline list of what viruses are present.
Water & Wastewater News, 6 October 2009
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~dGossip
~tWorking with poultry linked to certain cancers
~w2009-11-05
According to the findings of a new study recently published in the journal Cancer Causes & Control, poultry workers may be at particularly high risk of developing several forms of cancer. The researchers suggest that viruses carried by birds may be a possible cause.The findings come from an ongoing study by researchers to identify job-related illnesses in the nation's 250,000 poultry processing workers. It found higher than expected rates of cancers of the sinuses, mouth and blood, as well as other forms of the disease, in poultry plant employees.The researchers said cancer-causing viruses transmitted during the handling and slaughter of chickens and turkeys, as well as environmental factors such as exposure to fumes generated during the wrapping, smoking and cooking of meat, along with other aspects of production, may be to blame for the increased rates of illness.Some of the viruses present in birds are found in the egg supply. And because many vaccines are made using chicken eggs as incubators, the viruses have also been found in the vaccine stock - in particular, the shots against measles, mumps, and yellow fever, according to the researchers. However, the researchers have not detected any evidence that the presence of the viruses is harmful to humans.Still, "These observations have serious public health implications and reiterate the urgent need for studies to be conducted in subjects that have high exposure to the (cancer-causing) viruses of poultry, such as workers in poultry slaughtering and processing plants," they wrote.Eric Johnson, an epidemiologist at the University of North Texas Health Science Centre, in Fort Worth, and led author of the study said the viruses pose no risk to consumers who eat properly cooked poultry products, including eggs. But eating raw or undercooked eggs and poultry or handling raw meat may be hazardous, he said. During the study, the researchers compared cancer deaths in 2,580 members of the Baltimore meat cutter's union who worked exclusively in six Maryland poultry plants between 1954 and 1979. By 2003, 790 of those workers had died, and the researchers were able to determine the cause of death for 756.
Out of the 756 total deaths, 187 were from cancer. Although the overall death rate from cancer was not unusually high, the death rate was much greater-ranging from 3.5 to nearly 9 times higher-for several forms of the disease, including cancer of the tonsils, nasal cavity and sinuses, and a blood cancer called myelofibrosis.Death rates from certain cancers-including of the tongue, liver and oesophagus-also were higher than normal among various groups of workers even when the overall rates were what would be expected in unremarkable, the researchers said.For certain cancers, the risks were greater depending on the workers' sex or race. Those differences may reflect divisions of labour in poultry plants, where women and men, and whites and blacks, historically were assigned different duties, the researchers noted.Richard Lobb, a spokesman for the National Chicken Council, an industry group, dismissed the study as an "astounding piece" of flawed research. Lobb said the researchers did not adequately account for the known cancer risks of tobacco and alcohol use in the workers.In addition, the "suggestion that raw chickens carry viruses that cause cancer in humans is pure supposition unsupported by any scientific facts or studies," he said.Johnson acknowledged that the study's inability to account for the effects of tobacco and alcohol use was a limitation. But he said other research has shown that poultry and meat industry workers have higher-than-normal odds of developing cancer, even after controlling for smoking.What's more, smoking and alcohol are not linked to the blood cancers that seem to be more common among poultry workers in the new research, he said. Furthermore, Johnson said, the link between avian viruses and cancer in animals is well established. "We've known that for years. It's just that we've never had the human evidence," he said. "That's what we are providing for the first time."
Reuters Health, 2 November 2009
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~dGossip
~tSignificant bisphenol A levels in canned food - Study
~w2009-11-05
A new study has discovered significant levels of bisphenol A (BPA) in a wide variety of canned food that, for some, could approach levels shown to cause harm in animal studies, according to the Consumers Union (CU). The US non-profit group’s conclusion came following the testing of 19 canned foods - including soups, juice, tuna, and green beans – and found almost all contained “measurable levels of BPA”. The highest levels of the chemical were detected in some samples of green beans and soups, added the CU. In addition, the study demonstrates that the substance can be found in a wide range of canned goods including those labelled as organic and BPA-free, said the body. Its study also claimed that tests of a small number of “comparable products in alternative types of packaging showed lower levels of BPA in most, but not all cases”. CU Director of Technical Policy Dr. Urvashi Rangan said: “The findings are noteworthy because they indicate the extent of potential exposure. Children eating multiple servings per day of canned foods with BPA levels comparable to the ones we found in some tested products could get a dose of BPA near levels that have caused adverse effects in several animal studies.” BPA, which is used in the manufacture of polycarbonate and other plastics, has been linked to cardiovascular disease and diabetes in humans and disrupted reproductive development in animals. The chemical is commonly found in drinking bottles, baby bottles and sipper cups as well as in the lining of aluminium food and beverage cans. However, industry bodies such as the American Chemistry Council (ACC) have insisted BPA is safe – citing opinions from most major food safety bodies across the globe that the chemical poses no health risk to humans at the specified exposure levels. The CU acknowledged that its study had limitation and that the tests only “convey a snapshot of the marketplace and do not provide a general conclusion about the levels of BPA in any particular brand or type of product tested”. Levels in the same product purchased at different types or places or in other brands of similar foods might differ from CU test results, it said.