Page 226 - Concise Pathology for Exam Preparation ( PDFDrive )

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Environmental and

Nutritional Pathology

Q. Write briefly about environmental toxins.
Ans. Environmental pathology can be induced due to personal or occupational exposure to
toxins. Environmental toxins are the contaminants released into natural environment that cause
instability in the ecosystem and harm to the living organisms inhabiting it. Xenobiotics are
environmental toxins that may be absorbed into the body by inhalation, ingestion or through
the skin and mucosal surfaces. They include naturally occurring toxic substances like carbon
dioxide, hydrogen sulphide and volcanic gases, or industrial waste like heavy metals (lead,
cadmium, etc.), pesticides used in agriculture and industry, chlorine and other disinfectants
and wood preservatives. When the ability of our bodies to defend these toxins is exceeded or
when our bodies fail to break down or remove these toxins, serious damage may ensue. Self-
induced exposure or addictions to certain substances can result in health effects. These include
alcohol, tobacco and drugs like opioid narcotics, cannabinoids and sedative-hypnotics.

Alcohol
• Ethanol is mainly absorbed in the stomach and small intestine; depending on the blood
levels, it is then distributed to all tissues and fluids of the body.
• Drunk driving in most states is defined as a concentration of 80 mg/dL in the blood;
inebriation generally results at a blood alcohol level of 200 mg/dL and coma, death and
respiratory arrest usually occur at levels of 300–400 mg/dL.
• Habitual drinkers can tolerate blood alcohol levels up to 700 mg/dL. This metabolic
tolerance is attributed to an increased induction of the cytochrome P-450 xenobiotic-
metabolizing enzyme CYP2E1, which accelerates the metabolism of ethanol as well as
that of other drugs and chemicals like cocaine and acetaminophen.
• Methanol is metabolized to formaldehyde and formic acid, resulting in metabolic
acidosis, dizziness, vomiting, blurred vision or blindness and respiratory depression.
• Ethanol in blood is transformed to acetaldehyde in the liver by three enzyme systems.
Ethanol acetaldehyde acetate
• Alcohol dehydrogenase Aldehyde
• Microsomal ethanol dehydrogenase
oxidation system (MEOS) (ADH)
• Catalase (minor pathway)
Adverse Effects of Alcohol

1. Acute effects: Acute alcohol intake exerts its effects mainly on CNS, but can also induce
hepatic and gastric damage. The following are chief manifestations of acute alcoholic toxicity:
(a) CNS: Disordered cortical, motor and intellectual behaviour followed by CNS depression
(b) Liver: Acute alcoholic hepatitis (manifests with fever, right hypochondrial tender-
ness, jaundice and histology of the liver shows focal hepatocyte necrosis, Mallory
hyaline, neutrophilic infiltrate and fat accumulation)
(c) Stomach: Acute gastritis or ulceration
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