Presented by -
Shreyasi Singh
M.Sc IInd year
SES, JNU
INTRODUCTION
Formaldehyde is a colorless, strong-
smelling, flammable chemical that is
produced industrially and used in A simple volatile organic
building materials such as compound (HCHO)
particleboard, plywood, wallpaper and
paints.
Easily becomes a gas at
In addition, it is commonly used as room temperature, which
fungicide, germicide and disinfectant makes it part of volatile
and as a preservative in mortuaries organic compounds (VOCs)
and medical laboratories. Naturally occurring in
It is also a combustion product found Widespread
in tobacco smoke. the environment and also
Formaldehyde is produced
exposure in produced
endogenously by enzymatic and occupational and endogenously in the
nonenzymatic pathways or as a residential settings human body
detoxification product of xenobiotics Recognized as a Group
during cellular metabolism (ATSDR 1 human carcinogen
1999) by IARC
Linked to
respiratory
toxicity,
genotoxicity
ABSORPTION
Routes: inhalation
(primary), dermal, oral
Inhaled formaldehyde is absorbed
Rapid absorption in
primarily in the upper airways because
upper respiratory tract.
of its high water solubility, metabolism, The nasal and
and reactivity. nasopharyngeal mucosa
Initially contacts the mucus layer lining the are its target tissues
epithelium, formaldehyde undergoes a
reversible reaction with water to form
methanediol. In humans, oral breathing
Albumin in the mucus that lines the human bypasses the uptake in the
nasal epithelium forms an additional nasal epithelium; this
breathing pattern leads to
barrier to the systemic absorption of
increased delivery of
formaldehyde. The solubility of formaldehyde to the
formaldehyde in mucus and the ciliary intermediate regions of the
movement and ingestion of mucus may respiratory tract (that is, from
account for the removal of as much as the oral cavity to the upper
conducting airways of the
42% of the inhaled dose(Schlosser 1999). lungs) (Overton et al. 2001).
DISTRIBUTION
Some inhaled formaldehyde
passes through the mucus layer
to reach the epithelium where its
transformation and removal occur
by enzymatic reactions with the
nasal tissue and nonenzymatic
reactions with glutathione and
macromolecules, including
proteins and DNA
Schematic representation of the mammalian nasal epithelium. Formaldehyde crossing the
basement membrane can react further with macromolecules in the submucosal layer or reach the
systemic circulation. The figure also shows a representation of the nasal-associated lymphoid tissue
(NALT) on either side of the nasal septum and near the ventral nasopharyngeal duct. The NALT is
the site of formaldehyde interactions with lymphoid tissues,
METABOLISM
These metabolic processes contribute to the short biologic half-life of
formaldehyde.
ELIMINATION
MacAllister et al. evaluated the
48
excretion pathways of this
pollutant in animal models and
concluded that the main
pathway is exhalation (40%),
followed by urine (17%), and
feces (4%).
Formaldehyde disappears from
the plasma with a half-time of
about 1–1½ minutes, most of it
being converted to carbon
dioxide and exhaled via the
lungs. Smaller amounts are
excreted in the urine as formate
salts and several other
metabolites
TOXICITY
Formaldehyde is highly reactive at the site of entry and reacts readily with
macromolecules, including DNA to form DNA-protein (DPX) and DNA-DNA (DDX) cross-
links.
Formaldehyde-induced DNA damage is postulated to lead to mutations and clastogenesis,
critical cytogenetic events in the carcinogenic mode of action.
DPX cross-links, chromosomal aberrations, micronuclei, and sister-chromatid exchanges.
Genotoxicity occurs in the nasal mucosa and peripheral (circulating) blood lymphocytes
Formaldehyde causes myeloid and rare cancers, including
leukemia , and .
cancers of the paranasal sinuses, nasal cavity nasopharynx
Local Toxicity Neurotoxicity
•Primary site of Occupational
action: respiratory tract studies suggest
(especially nasal effects on
epithelium)
•Causes irritation of
cognitive function
eyes, nose, throat and behavior
•Induces Interfere with
inflammation, mucus acetylcholinesteras
hypersecretion, and e activity in exposed
tissue damage workers
REFERENCES
Bernardini, L., Barbosa, E., Charão, M. F., & Brucker, N. (2022).
Formaldehyde toxicity reports from in vitro and in vivo studies: a review
and updated data. Drug and chemical toxicology, 45(3), 972-984.
Songur, A., Ozen, O. A., & Sarsilmaz, M. (2009). The toxic effects of
formaldehyde on the nervous system. Reviews of environmental
contamination and toxicology, 105-118.
Zhang, L. (2018). Formaldehyde: exposure, toxicity and health
effects (Vol. 37). Royal Society of Chemistry.
Review of the Environmental Protection Agency’s Draft IRIS Assessment
of Formaldehyde.
Formaldehyde in occupational environments: literature review and an
occupational health surveillance proposal
Bogdanffy, M.S., P.H. Morgan, T.B.Starr, and K.T. Morgan. 1987. Binding of
formaldehyde to human and rat nasal mucus and bovine serum
albumin. Toxicol. Lett. 38(1-2):145-154
Casanova, M., H.d’A. Heck, J.I. Everitt, W.W. Harrington, Jr., and J.A. Popp.
1988. Formaldehyde concentrations in the blood of Rhesus monkeys
after inhalation exposure. Food Chem. Toxicol. 26(8):715-716.
