Summer in Israel: Why do we perspire more in hot weather?

And what harms a household’s air quality?

Thousands flock to Tel Aviv beaches during April 22 heat wave.  (photo credit: AVSHALOM SASSONI/MAARIV)
Thousands flock to Tel Aviv beaches during April 22 heat wave.
With the hot summer weather upon us, we should expect to perspire more! But why do we sweat especially in hot weather? The answer is simple. Sweating is the mechanism of the body to cool the surface of the body.
It is common knowledge that our body temperature has to be maintained at 37º centigrade. The sweat that covers the skin surface evaporates in hot weather, and evaporation of the sweat cools our skin surface. A related problem with the hot weather is that in long treks, we should also be concerned about dehydration as a result of over sweating. So, what is the source of our perspiration? The source of the fluid that our sweat glands secrete is the fluid that is found in between our cells. This fluid is salty with a high concentration of salt – sodium chloride (NaCl). But, relative to the body fluid, the concentration of salt is much less in sweat. While the sweat fluid passes through the sweat ducts the, sodium ions in the fluid are reabsorbed back to the body.
Until now, the channel through which sodium returns to the body was not identified. A recent study published by a team of researchers from the Sackler School of Medicine of Tel Aviv University, Ariel University and Holon’s Wolfson Medical Center reported for the first time visualization of the sodium channels that are responsible for the reabsorption of sodium ions in the human skin.
This study was led by senior Ariel University professor of biochemistry and molecular biology Israel Hanukoglu, his brother Prof. Aaron Hanukoglu, a senior pediatric endocrinologist at Wolfson and others. The research was carried out to understand the mechanism for the significant loss of sodium ions in infants and children who suffer from a very rare hereditary disorder called systemic pseudohypoaldosteronism. Earlier studies by the same group of researchers had identified that this disease results from mutations in the genes that code for sodium channel proteins. Especially in hot weather conditions, the loss of sodium via perspiration may aggravate the symptoms of this disease, which is accompanied by severe dehydration. Severe salt loss from sweat glands, in addition to salt loss from the kidney, requires recurrent hospitalization to replace the fluid and salt loss in these patients.
For this study, the researchers prepared specific antibodies that recognize this channel in tissue sections. The skin includes multiple tiny organs, including epidermis that serves as a protective layer, hair follicles through which hairs grow, smooth muscle cells that can lead to contraction of skin and several types of sweat glands.
To visualize the location of the channel proteins, the researchers scanned skin sections at high resolution using laser-activated fluorescent-colored antibodies. While the expression of the channel proteins was detected in all mini-organs throughout the epidermis, only in one special sweat gland, called eccrine sweat glands, the channel proteins were localized in the sweat ducts.
The findings reported by the authors indicate that the sodium channels in the eccrine sweat gland ducts are responsible for the uptake of salt while the sweat is still in the duct of the sweat gland. Thus, while all the fluid is excreted, the salt present in the sweat is recycled into the body, to avoid loss of salt and thus to prevent dehydration, especially in hot climates. It has been also suggested that with their widespread localization in other skin appendages ENaC may be involved in skin wound healing.
An ambitious new study led by San Diego State University researchers has found that cigarette and marijuana smoking, as well as candles, cleaning products and frying food, all harm a household’s air quality. Not surprisingly, cigarette smoke emerged as a major source of airborne particles in homes with smokers, but other products used at also jumped out as in-home air polluters. The findings are especially relevant to families with children living in low-income households who are at greater risk of health problems resulting from poor air quality.
“Our primary goal was to figure out what’s happening in houses that leads to higher air particle levels and, in turn, unhealthy environments for children,” said study coauthor John Bellettiere, a graduate student in public health.
A research team led by environmental health expert Dr. Neil Klepeis, behavioral health researcher Dr. Melbourne Hovell and co-investigator Suzanne Hughes studied the environments of 300 families living in San Diego with at least one child aged 14 and younger and one smoker.
They installed a pair of air-particle monitors in each of the homes – one in the area of the house closest to where smoking usually occurs and one in the child’s bedroom.
The monitors continuously scan the air for fine particles between 0.5 and 2.5 micrometers in size – a range that includes dust, fungal spores, auto emissions and combustion byproducts. These particles are of a size that can reach deep into the lungs, where they can influence a variety of health complications including breathing and cardiovascular problems.
Over the course of three months, the monitors transmitted air quality data from the homes back to the researchers. The scientists correlated the households’ activities with their respective air quality monitor data and a clear picture emerged.
Homes that reported cigarette smoking indoors had a median particle level that was nearly double that of homes without indoor smoking. These particles contain nicotine and combustion byproducts well known to be dangerous to people’s health, especially that of children.
Interestingly, marijuana smoking contributed to in-home air pollution about as much as tobacco smoking – the first time such a finding has been reported. Finally, burning candles and incense, frying food in oil and spraying cleaning products also increased the number of fine particles in the air. The researchers reported their findings today in the journal PLoS One.
“The aim of our research is, ultimately, to find effective ways to promote smoke-free homes and also to find good strategies, in general, for reducing exposure to household pollution,” Klepeis said. “The findings from our work will allow for better education and feedback to families.”