The development of a respiratory tract model which accurately
reflects reality is a difficult and complicated effort. This stems largely
from the variety of airway shapes, airflow patterns, and cell types
having different radiosensitivities. Anatomic and physiologic alterations
in smokers or those exposed to chemicals, among others, further
complicate modeling. In spite of the inherent difficulties, the
continuing pursuit of a model that mimics actual conditions has been
considered to be important by those involved in radiation protection....
Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Ferrets develop fatal influenza after inhaling small particle aerosols of highly pathogenic avian influenza virus A/Vietnam/1203/2004 (H5N1
This contribution book collects reviews and original articles from eminent experts working in the interdisciplinary arena of novel drug delivery systems and their uses. From their direct and recent experience, the readers can achieve a wide vision on the new and ongoing potentialities of different drug delivery systems. Since the advent of analytical techniques and capabilities to measure particle sizes in nanometer ranges, there has been tremendous interest in the use of nanoparticles for more efficient methods of drug delivery.
The infectiousness of a TB patient is directly related to the number of droplet nuclei carrying
M. tuberculosis (tubercle bacilli) that are expelled into the air. Depending on the environment, these tiny particles can remain suspended in the air for several hours. M. tuberculosis is transmitted through the air, not by surface contact. Infection occurs when a person inhales droplet nuclei containing
M. tuberculosis, and the droplet nuclei traverse the mouth or nasal passages, upper respiratory tract, and bronchi to reach the alveoli of the lungs.
Such a comprehensive model allows
for the modeled deposition of submicrometer aerosols (nanosized particles and
particulate matter sizes larger that nano to determine the total deposition as well as
localized deposition of particles). The results are important, prospectively, since they
may lead to a better understanding of the developmental respiratory physiology and
the associated effects on children’s health response to environmental pollutants, or the
medical outcome from inhalation therapy for infants and children from nanoparticlecontaining
Although the part of our bodies most affected by air pollution is the respiratory
system, the circulatory system can also be affected. Exposure to unhealthy levels
of air pollutants can result in low oxygen levels in red blood cells, abnormal heart
rhythms, and increased risks of blood clots and narrowing of blood vessels. These
effects can lead to worsening of heart diseases such as heart failure and increased
risks of heart attacks or strokes.
The Pollutants Chart: Sources and Effects of Air Pollutants summarize the sources
and health effects of criteria air pollutants.
In order to provide comparable estimates of exposure to outdoor air
pollution for all 14 WHO regions, models developed by the World Bank
were used to estimate concentrations of inhalable particles (PM10) (Pandey
et al., 2004). Specifically, economic, meteorologic, and demographic data
and available PM measurements in 304 cities were used to estimate PM10
levels in all 3211 cities worldwide with populations greater than 100,000 and
Particles, as noted above, can provide an
exposure pathway for SVOCs, but they
also can present a serious health risk on
their own. They range in size from very
small (0.001 μm to 10 μm), which can
remain in the air for a long time, up to
relatively large (100 μm), which quickly
settle out of calm air. Inhaling particulates
can cause eye, nose, and throat irritation
and can increase the risk for respiratory
infections. Health care professionals are
especially concerned about the long-term
effects of inhaling ultrafine particles
(less than 2.
The thought of mucus disturbs many people. Mucus is beneficial as the first
defense of the airways. The mucus lining traps inhaled particles and allows them
to be cleared from the airway by cilia and cough. The mucus layer also prevents
dehydration and desiccation of the airway surface and provides a nutrient milieu
for the ciliated epithelium. Mucus can also be quite bad. Airway mucus retention
due to hypersecretion or poor mucus clearance is a characteristic of many airway
diseases including cystic fibrosis, chronic bronchitis, bronchiectasis, and asthma.
Other studies, primarily with laboratory animals, suggest that the chemical composition5
and surface areas of the particles may be more important than particle mass. Scientists
are continuing to study the health effects of particles and are developing better methods
for measuring the important constituents. It may be possible in the near future to more
accurately assess the effects of inhaled particles on human health.
Nitrogen oxides are produced during most combustion processes. Mobile sources and
power plants are the major contributors in Southern California.
M. tuberculosis is carried in airborne particles, called droplet nuclei, of 1–5 microns in diameter. Infectious droplet nuclei are generated when persons who have pulmonary or laryngeal TB disease cough, sneeze, shout, or sing. Depending on the environment, these tiny particles can remain suspended in the air for several hours. M. tuberculosis is transmitted through the air, not by surface contact. Transmission occurs when a person inhales droplet nuclei containing M.
Thus, ultrafine dusts of the same dimensions as nanoparticles mainly penetrate the body via
inhalation and are deposited in the lungs. A portion of these dusts can be distributed directly to
the brain via the olfactory nerves. The lungs do not necessarily succeed in totally eliminating
these undesirable particles, which then cause pulmonary inflammation. This can lead to the
development of lung diseases specific to the nature of the dusts that caused them.