Formaldehyde (CH2O) is a flammable
and colorless toxic gas with a strong chemical smell found in building
materials and many household products. Formaldehyde can be found naturally
occurring in environments produced in small amounts by most living organisms as
part of normal metabolic processes (National Cancer Institute, 2011). However,
the general population is mostly exposed to indoor sources of formaldehyde
present in the manufacture of resins used in pressed-wood products, insulation
materials as well as glues and adhesives. Though small dose of formaldehyde is
considered safe but high concentration can increase risks of sickness while
prolonged exposure can lead to chronic diseases. The International guideline
values and recommendations for indoor formaldehyde for Hong Kong is between 30 µg
m-3 to 100 µg m-3 and exceeding this recommended level can have
negative impact on human health.
In a study conducted by Tang et al., (2009)
which examines formaldehyde in China and its potential impact on human health.
China has displayed unprecedented economic growth in the last 20 years and it
has also become the largest producer and consumer of formaldehyde. Over 65
percent formaldehyde produced in China is used in the synthesis of resins
including urea-formaldehyde (UF), phenol-formaldehyde (PF) materials which are
associated with indoor air pollution (Tang et al., 2009). Displayed in figure 1
represents the total distribution of formaldehyde consumption in China (A) and
global distribution (B). The increase production and usage of formaldehyde in
building materials puts the Chinese population at increased risk for cancer and
other associated health effects. Formaldehyde poisoning has been correlated
with allergy, asthma, pulmonary damage, cancer and in some cases even deaths.
Formaldehyde concentration between 0.5 and 1.0 ppm are most likely to cause
nose and throat irritation and concentration level in China often exceeds the
recommended levels. Modern homes and fuel burning are the two top mechanisms
responsible for indoor formaldehyde pollution globally. Many reports indicate
indoor formaldehyde decrease in concentration with time, falling below 0.1 mg/m3
within 6 months. However, data indicates concentration can still remain high
after 1 year of renovation and this can be explained by the lack of air
exchange. In a study conducted in Jiangxi province, formaldehyde concentration
remains as high as 0.25 mg/m3 even up to after 1 year in newly
refurbished bedrooms. Workers in certain occupation are at particular high risk
compared to the general population. Occupational Exposure Limit (OEL) for
formaldehyde is 0.5 mg/m3 and despite such low concentrations, many
workers are exposed to higher levels. The average occupational level exceeded
0.5 mg/m3 and in one cases surpassed 46.14. mg/m3. (Gao
et al., 1988). This indicates workers in garment and wood manufacturing
constantly exposed to high levels have a higher risk of formaldehyde related
sickness. Additionally, formaldehyde can also be detected in food. Because
formaldehyde is a natural metabolite in many living things, and is thus present
in many foods we find in our local supermarkets. Shiitake mushrooms have a
formaldehyde concentration from 40 to 380 mg/kg and high concentration can also
be detected in mackerel, squid, red shrimp and many marine products (Wang et
al., 2007a). Sixty students in middle school reported symptoms of nausea, vomit
and experienced dizziness after consumption of formaldehyde preserved Pacific
saury fish. A further report documented thirty-eight middle school staffs
reported consuming formaldehyde preserved fish experienced similar symptoms.
This is a clear indication more stringent regulation is required on the usage
of formaldehyde in food (Li and Song, 2006; Zhang et al., 2006a). Though
formaldehyde occur naturally in the environment, human induce actions can
further increase concentration. Examples such as the illegal usage of
formaldehyde in food preservatives has exceeded 300 mg/kg and in some cases,
reaching 4250 mg/kg. Not only marine products exceeded allowable level, but
fresh fruits also exhibited formaldehyde concentration above recommended level.
Fresh fruits measured average formaldehyde level between 2.74 mg/kg but after
refrigeration, level increased 2.3-3.8 times (Ma et al., 2007).
Indoor formaldehyde has a negative impact on human health and it can
result in acute poisoning, irritation, dermal allergies, allergic asthma, and
can even damage pulmonary functions. Upon direct contact on skin, formaldehyde
can cause acute mucus membrane irritation often leading to dry skin,
dermatitis, tearing eyes, sneezing and coughing. When high concentration of
formaldehyde is exposed, serious side effect includes nasal and pharyngeal
disease as well as laryngospasm and pulmonary edema. According to Li, (1997),
one man’s face exposed to large amounts of formalin suffered facial swelling and
cornea degeneration. Formaldehyde exposure is also reported by Wang et al.,
(1999); Zhang et el., (1999) where an employee experienced pharyngeal
congestion, chronic rhinitis and decreased olfactory function. Similar cases
were documented at a manufacturing plants when 66 workers exposed to
formaldehyde reported increased occurrence of congestion in cornea, nasal
membrane, and pharynx. Formaldehyde is also known to cause dermal allergies.
Cases of dermatitis has been reported in factories where concentration was between 0.60-23 mg/m3
accompanied by swelling, red spots, irritation, pain and burning sensation. Furthermore,
there have been six reports of formaldehyde related pulmonary disorders.
Factory workers exposed to concentration between 3.07 ± 5.83
mg/m3 experienced abnormal pulmonary function and discovered
obstruction in the small airways as well as decrease in pulmonary ventilation.
recommended formaldehyde concentration in Hong Kong is displayed in figure 2.
Formaldehyde level in 8-h average <30 µg/m3 is considered excellent whereas <100 µg/m3 is considered good class (Guo et al., 2009).
However, figure 2 only represents formaldehyde level for the general population
which includes infants, children, adults and elders. The recommended level of
formaldehyde is drastically different for occupational standards because
workers are constantly exposed to higher amounts therefore, workers around high
level of formaldehyde are at particular risk of sickness. There are many
actions that can be conducted to reduce indoor formaldehyde concentrations. Individual
can purchase wood products that contains lower level of formaldehyde is an
option as well as selecting wood furniture coatings that use cellulose nitrate,
acrylic, ultraviolet drying instead of resins. Ventilation is recommended
inside buildings because it allows for a greater exchange of air flow hence,
will be able to dilute pollutants by introducing a sufficient flow of outdoor
air (Institute de recherché Robert-Sauvé en santé et en sécurité du travail
(IRSST), 2006). In working environments that contain high level of
formaldehyde, regulation on personal protective equipment is mandatory. Self-contained
breathing apparatus must be worn when level exceeds above 20ppm, under 20ppm,
filter cartridge mask is recommended.
is a toxic colorless gas with a strong chemical smell that is released into the
environment mainly from wood products. It is also found in food products and
consumption of marine products containing traces of formaldehyde can lead to
detrimental health effects. It is imperative that when exposed to high level of
formaldehyde, it is imperative to wear personal protective equipment such as
self-contained breathing apparatus or filter cartridge mask.