Wednesday, April 09, 2014

Coughs and sneezes staying airborne

Cold and flu pathogens may stay airborne for long
distances after a sneeze or a cough, researchers say.
The next time you feel a sneeze coming on, raise your elbow to cover up that multiphase turbulent buoyant cloud you're about to expel.

That's right: A novel study by MIT researchers shows that coughs and sneezes have associated gas clouds that keep their potentially infectious droplets aloft over much greater distances than previously realized.

"When you cough or sneeze, you see the droplets, or feel them if someone sneezes on you," says John Bush, a professor of applied mathematics at MIT, and co-author of a new paper on the subject.

"But you don't see the cloud, the invisible gas phase. The influence of this gas cloud is to extend the range of the individual droplets, particularly the small ones."

Indeed, the study finds, the smaller droplets that emerge in a cough or sneeze may travel five to 200 times further than they would if those droplets simply moved as groups of unconnected particles � which is what previous estimates had assumed.

The tendency of these droplets to stay airborne, resuspended by gas clouds, means that ventilation systems may be more prone to transmitting potentially infectious particles than had been suspected.

With this in mind, architects and engineers may want to re-examine the design of workplaces and hospitals, or air circulation on airplanes, to reduce the chances of airborne pathogens being transmitted among people.

"You can have ventilation contamination in a much more direct way than we would have expected originally," says Lydia Bourouiba, an assistant professor in MIT's Department of Civil and Environmental Engineering, and another co-author of the study.

The paper, "Violent expiratory events: on coughing and sneezing," was published in the Journal of Fluid Mechanics.

It is co-written by Bourouiba, Bush, and Eline Dehandschoewercker, a graduate student at ESPCI ParisTech, a French technical university, who previously was a visiting summer student at MIT, supported by the MIT-France program.

Smaller drops, longer distances

The researchers used high-speed imaging of coughs and sneezes, as well as laboratory simulations and mathematical modeling, to produce a new analysis of coughs and sneezes from a fluid-mechanics perspective.

Their conclusions upend some prior thinking on the subject. For instance: Researchers had previously assumed that larger mucus droplets fly farther than smaller ones, because they have more momentum, classically defined as mass times velocity.

That would be true if the trajectory of each droplet were unconnected to those around it. But close observations show this is not the case; the interactions of the droplets with the gas cloud make all the difference in their trajectories. Indeed, the cough or sneeze resembles, say, a puff emerging from a smokestack.

A cough or sneeze is a "multiphase turbulent buoyant cloud," as the researchers term it in the paper, because the cloud mixes with surrounding air before its payload of liquid droplets falls out, evaporates into solid residues, or both.

"The cloud entrains ambient air into it and continues to grow and mix," Bourouiba says. "But as the cloud grows, it slows down, and so is less able to suspend the droplets within it. You thus cannot model this as isolated droplets moving ballistically."

The MIT researchers are now developing additional tools and studies to extend our knowledge of the subject. For instance, given air conditions in any setting, researchers can better estimate the reach of a given expelled pathogen.

Source: EurekAlert

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Tuesday, February 25, 2014

Breathing air pollution may be as toxic as cigarette smoke for pregnant women

Photo: Adamr/freedigitalphotos.net
Breathing the air outside their homes may be just as toxic to pregnant women —if not more so — as breathing in cigarette smoke, increasing a mom-to-be’s risk of developing deadly complications such as preeclampsia, according to findings from a new University of Florida study.

UF researchers compared birth data with Environmental Protection Agency estimates of air pollution, finding that heavy exposure to four air pollutants led to a significantly increased risk for developing a high blood pressure disorder during pregnancy. The research was published in the January issue of the Journal of Epidemiology and Community Health.

The pollutants include two specific types of fine and coarse particulate matter, carbon monoxide and sulfur dioxide. According to the EPA, particulate matter includes acids, dust, metals and soil particles. These inhalable particles are released from industries and forest fires and can form when gases react with each other in the air. Sulfur dioxide is emitted from power plants and industries. Most carbon monoxide is produced by car exhaust.

“Fetal development is very sensitive to environmental factors,” said Xiaohui Xu, M.D., Ph.D., an assistant professor of epidemiology in the colleges of Public Health and Health Professions and Medicine. “That is why we wanted to do this research. Hypertension (high blood pressure), in particular, is associated with increased morbidity and mortality, causing a lot of problems for the mother and fetus, including preterm delivery.”

Hypertensive disorders such as gestational hypertension, preeclampsia and the deadly condition it leads to, eclampsia, affect about 10 percent of pregnancies. Despite the serious risks to mother and baby, little is known about what specifically causes these conditions to develop in pregnant women, the researchers say.

Although more studies are needed, the researchers hypothesize that exposure to air pollution during pregnancy may affect a woman’s normal pattern of blood pressure.

“We also want to look at preterm delivery and low birth-weight and find out what the effects of breathing contaminated air are on fetal development.” Xu said.

Wednesday, February 19, 2014

What percentage of your food has some type of packaging? It may be making you sick.

photo: antpkr/freedigitalphotos.net
Think of your last trip to the grocery store -- it's likely that even your vegetables may be housed in some type of packaging. 

Scientists are now concerned that all those synthetic chemicals used in the packaging, storage, and processing of foodstuffs might be harmful to human health over the long term.

In a commentary in the Journal of Epidemiology and Community Health, the researchers say that most of these substances are not inert and can leach into the foods we eat.

Despite the fact that some of these chemicals are regulated, people who eat packaged or processed foods are likely to be chronically exposed to low levels of these substances throughout their lives, say the authors.

And far too little is known about their long term impact, including at crucial stages of human development, such as in the womb, which is "surely not justified on scientific grounds," the authors claim.

They point out that lifelong exposure to food contact materials or FCMs - substances used in packaging, storage, processing, or preparation equipment - "is a cause for concern for several reasons."

These include the fact that known toxicants, such as formaldehyde, a cancer causing substance, are legally used in these materials. Formaldehyde is widely present, albeit at low levels, in plastic bottles used for fizzy drinks and melamine tableware.

Secondly, other chemicals known to disrupt hormone production also crop up in FCMs, including bisphenol A, tributyltin, triclosan, and phthalates.

"Whereas the science for some of these substances is being debated and policy makers struggle to satisfy the needs of stakeholders, consumers remain exposed to these chemicals daily, mostly unknowingly," the authors point out.

And, thirdly, the total number of known chemical substances used intentionally in FCMs exceeds 4000.

Furthermore, potential cellular changes caused by FCMs, and in particular, those with the capacity to disrupt hormones, are not even being considered in routine toxicology analysis, which prompts the authors to suggest that this "casts serious doubts on the adequacy of chemical regulatory procedures."

They admit that establishing potential cause and effect as a result of lifelong and largely invisible exposure to FCMs will be no easy task, largely because there are no unexposed populations to compare with, and there are likely to be wide differences in exposure levels among individuals and across certain population groups.

But some sort of population-based assessment and biomonitoring are urgently needed to tease out any potential links between food contact chemicals and chronic conditions like cancer, obesity, diabetes, neurological and inflammatory disorders, particularly given the known role of environmental pollutants, they argue.

"Since most foods are packaged, and the entire population is likely to be exposed, it is of utmost importance that gaps in knowledge are reliably and rapidly filled," they urge.


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Tuesday, February 18, 2014

Study to look into possible links between air pollution and brain cancer

Photo: ddpavumba/freedigitalimages.net
Researchers at Cedars-Sinai have been awarded a $1 million grant to determine if several potentially toxic compounds that exist in polluted air are capable of entering the brain from the bloodstream and causing brain cancer.

The Brain and Lung Tumor and Air Pollution Foundation is providing the funds for the south coast air quality management district study.

The National Toxicology Program, an interagency program of the U.S. Department of Health and Human Services and the Institute of Environmental Health Services, has identified 13 chemicals that have caused brain tumors. The Cedars-Sinai study will focus on three – naphthalene, butadiene and isoprene – that often are associated with polluted air.

Naphthalene, used in the plastics industry and a component of mothballs and other products, may be released into the air when coal and oil are burned. Butadiene, used in rubber manufacturing and found in vehicle exhaust, exists in low levels in the air of urban and suburban areas. Isoprene, a natural compound produced by certain trees and shrubs, is used in manufacturing synthetic rubber and adhesives. Alone, it usually is not considered an air pollutant, but when it mixes with high levels of nitric oxide – which often occurs in industrial areas – the combination produces "ground-level" ozone, which can be harmful when inhaled.

The air pollution study is intended to determine whether up to 12 months of ongoing exposure to air pollution causes molecular changes in the brain that are consistent with the development of brain tumor pathways and  if toxins associated with air pollution can cross the brain's natural defense mechanism – the blood-brain barrier.

"Most studies looking at central nervous system cancers have focused on occupational hazards and have found that many manufacturing, farming, chemical and other industries are associated with increased risk. In this study, we will learn about particular components of air pollution and how they may be involved with the abnormal expression of genes and proteins that activate cancer stem cells. This may increase our understanding of air pollution as a potential risk factor for the generation of brain cancer," said Keith Black, MD, chair and professor of the Department of Neurosurgery, director of the Maxine Dunitz Neurosurgical Institute, director of the Johnnie L. Cochran, Jr. Brain Tumor Center and the Ruth and Lawrence Harvey Chair in Neuroscience.

Black is principal investigator of this study. He and other Cedars-Sinai researchers have conducted earlier studies on air pollution and molecular brain changes that could lead to cancer development – primarily on the potential effects of diesel fuel exhaust – for the South Coast Air Quality Management District.

In the new study, researchers will examine tissue exposed to pollutants at three months, six months and 12 months to determine if there is a change with longer exposure compared to shorter.

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Friday, February 14, 2014

Study: Breathing in smoke at home impairs child’s response to asthma treatment

Children exposed to cigarette smoke at home have lower levels of an enzyme that helps them respond to asthma treatment, a study has found.

Passive smoking is known to worsen asthma symptoms in children and impair their response to inhaled steroid treatment, but how this effect occurs was not known.

Researchers at Imperial College London found that children with severe asthma with a parent who smokes at home have lower levels of the enzyme HDAC2 compared with those whose parents don’t smoke. HDAC2 is required for steroids to exert their beneficial anti-inflammatory effects in asthma.

Professor Peter Barnes FRS, from the National Heart and Lung Institute at Imperial College London, said: “The mechanism we’ve identified makes children less sensitive to inhaled steroid treatment, so they suffer more symptoms and might have to take higher doses of steroids, which may lead to side effects.

“These findings underline the importance of legislation aimed at protecting children from being exposed to cigarette smoke. Restricting smoking in cars is a positive step, but the same should be applied in homes.”
The findings are reported in the journal Chest.

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