inflammation. However, there is no known med-
ical therapy to treat damage that has occurred to
the lungs. Damage that does occur to the lungs is
permanent and berylliosis is usually progressive,
tending to continue even after exposure to beryl-
lium ends. The resulting damage to the lungs may
lead to HEART FAILURE and other cardiovascular
health conditions because the HEARTcannot pump
enough BLOOD to oxygenate the body’s tissues.
LUNG TRANSPLANTATIONmay become a viable treat-
ment option for people who develop complete
pulmonary failure.
Risk Factors and Preventive MeasuresRecent research suggests GENETIC PREDISPOSITION
underlies most cases of berylliosis, with mutations
or defects affecting the MAJOR HISTOCOMPATABILITY
COMPLEX(MHC), which encodes aspects of immune
response. The role of genetic predisposition is not
entirely clear, though likely explains why some
people who have limited exposure develop serious
disease whereas others who have prolonged expo-
sure seem to experience no adverse effects. How-
ever, berylliosis occurs only in people exposed to
beryllium and nearly all such exposure is occupa-
tional, though beryllium is a natural mineral pres-
ent in the environment. Reducing this exposure
through appropriate occupational hygiene and
protective measures can significantly reduce the
risk of disease development.
MANUFACTURING JOBS WITH HIGH RISK
FOR BERYLLIOSIS
aerospace alloys computer electronics
dental alloys (bridges and crowns) electrode welding
electronic resistors heat sinks
jet brake pads jet turbine blades
laser tubes metal alloy bicycle frames
metal working nuclear weapons
semiconductor chips transistors
X-RAYwindows
People who work in industries in which beryl-
lium use is common should be alert to the early
symptoms of berylliosis. Contact with or use of
products containing beryllium after their produc-
tion or manufacture does not convey beryllium
exposure, however. Screening blood BeLPT tests
among people who work with beryllium can iden-
tify early indications of immune reactivity, allowing
medical intervention to avert extensive damage to
the lungs. OSHA recommends the use of powered
respirators with high-efficiency particulate air
(HEPA) filters and protective clothing in the work-
place, as well as safeguards, such as showering and
changing into complete street clothes (including
shoes) before leaving the workplace.
See also ASBESTOSIS; BYSSINOSIS; ENVIRONMENTAL
HAZARD EXPOSURE; HEAVY-METAL POISONING; OCCUPA-
TIONAL HEALTH AND SAFETY; SARCOIDOSIS.black lung See ANTHRACOSIS.breathing The process of drawing air into and
expelling air from the LUNGS, also called pul-
monary respiration. Specialized centers in the
brainstem regulate the rate and rhythm of respira-
tion to harmonize breathing with HEART RATEand
BLOOD PRESSURE. Breathing occurs through the
mechanical actions of MUSCLE movement. The
DIAPHRAGM(the large, flat muscle that extends
across the floor of the thoracic cavity) and the
intercostal muscles (the muscles between the ribs)
contract to expand the thoracic cavity, pulling air
into the lungs (inhalation). Inhalation is an active
process.
Simultaneously the EPIGLOTTIS, a cartilaginous
flap at the top of the throat normally closed across
the top of the TRACHEAto prevent food and other
materials from entering the lungs, opens to allow
the air to pass. The air flows through the trachea
into the bronchi, bronchioles, and alveoli. When
the diaphragm and the intercostal muscles relax
the thoracic cavity returns to its resting position,
pressuring air out of the lungs (exhalation) in
reverse sequence. Exhalation is a passive process.
Breathing patterns help the doctor assess pul-
monary function and respiratory effectiveness.
Breathing may be varying combinations of rapid
(TACHYPNEA) or slow (bradypnea), regular or irregu-
lar, deep or shallow. Though an individual may
influence breathing through conscious focus,
breathing is an involuntary process under control
of the brainstem. The concentration of carbon diox-
ide in the BLOODis the primary trigger for initiation
of a RESPIRATORY CYCLE(one inhalation and one
exhalation), triggering the brainstem to signal the
diaphragm and the intercostal muscles to contract.breathing 193