Investigation of Toxicity of Cigarette Butts Collected in Addis Ababa to Swiss Albino Mice
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Date
2016-01
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Addis Ababa University
Abstract
Background: Cigarette butts are the most common form of litter in the world;
approximately 5.6 trillion cigarettes are smoked yearly worldwide. Over 7000 chemicals
may be introduced to the environment in cigarette butts and smoke constituents. These
include chemicals such as nicotine, carbon monoxide, hydrogen cyanide, polycyclic
aromatic hydrocarbons, heavy metal ions, nitrosamines, ammonia, acetaldehyde,
formaldehyde, benzene, phenol and acetone, over 70 of which are carcinogenic to
humans. Environmental cigarette butts are toxic to microorganisms, fish, other marine
organisms and birds, but no studies have been done on their toxicity to mammals.
Methods: In this study the toxicity of cigarette butt leachates to Swiss albino mice was
investigated, and the effects of cigarette butts with and without associated tobacco were
compared. Cigarette butt leachates were made by soaking different numbers of cigarette
butts in 250 mL of tap water overnight, and leachates were given to mice to drink. The
weights of mice as well as amounts of food and fluids consumed were followed over
time. Necropsies were performed and tissues were weighed and evaluated by histological
staining with eosin and hematoxylin. Blood glucose and liver function tests (ALT, AST
and ALP) were also measured.
Results: Mice given high-concentration cigarette butt leachates during their growth from
6 weeks to 16 weeks preferred water over any of the leachates, whereas mice given lower
butt concentrations of leachates representative of the relative frequencies of butt types in
the environment drank butt leachates as well as water. Food intake was not affected by
cigarette butt leachates. Mean fasting blood glucose and activities of serum liver enzymes
were not different between mice given leachates or water to drink. The weights of the
mice, as well as tissues (liver, lung, spleen, heart, kidney, epididymal fat pads) were
significantly lower in mice that drank leachates with associated tobacco than in mice that
drank water alone or leachates made from butts without associated tobacco. This suggests
that a component(s) of tobacco is/ are responsible for reducing weight gain during mouse
growth. Cigarette butt leachates had no effect on histopathology of liver, heart and
kidney, whereas lung tissue of the mice that drank leachates made with tobacco-
associated butts showed increased air space volumes and alveolar fibrosis, compatible
with pulmonary emphysema.
Conclusions: Cigarette butts are toxic to laboratory mice, causing reduced weight gain
during growth, reduced mass and size of tissues and organs, and pulmonary
emphysematous changes. An average cigarette butt thrown into the environment contains
1.5 mg of nicotine, enough to potentially kill 15 mice. The implications of these studies
to environmental animals in Ethiopia and elsewhere are discussed
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Keywords
Toxicity; Cigarette