Chemistry International
Vol. 23, No. 4
July 2001
New Publications
from the World Health Organization
Carbon Monoxide, Environmental Health Criteria No. 213
1999, xxiv + 464 pages (English, with summaries in French and Spanish),
ISBN 92-4-157213-2, CHF 96.-/USD 86.40; In developing countries: CHF
67.20, Order No. 1160213. WHO Marketing and Dissemination, CH-1211 Geneva
27, Switzerland; Tel.: +41 22 791 24 76; Fax: +41 22 791 48 57; E-mail:
[email protected].
This book evaluates the risks to human health and the environment posed
by exposure to carbon monoxide, a colorless, odorless gas produced by
both natural and anthropogenic processes. Concerns about the potential
health effects of exposure have been addressed in extensive studies
with both humans and a range of animal species. Although studies of
carbon monoxide poisoning are included, the report gives major attention
to possible health risks linked to the relatively low concentrations
that characterize most exposures. The report also aims to identify subpopulations
that may be especially susceptible to adverse health effects. Close
to 1 000 references are included in this comprehensive assessment. Concerning
environmental levels arising from human activities, highway vehicle
emissions are considered the principal source, followed by emissions
from nonhighway transportation sources, other fuel combustion sources,
industrial processes, and solid waste disposal. Evidence from monitoring
stations supports the conclusion that environmental concentrations are
declining, reflecting the efficacy of emission control devices on newer
vehicles. The report also considers the factors that contribute to indoor
concentrations, with cigarette smoke singled out as a major source.
A chapter on environmental distribution and transformation summarizes
what is known about the environmental fate of carbon monoxide, its contribution
to ozone production in the troposphere, and its possible role in global
warming. Sources of personal exposure are considered in the next chapter,
which concludes that the most important exposures for the general population
occur in the vehicle and indoor macroenvironments. Several occupations
involving an increased risk of high exposures are also identified. Toxicokinetics
and mechanisms of action are reviewed in the next chapter, which discusses
the many factors that influence the concentrations of carboxyhemoglobin
in blood, and summarizes what is known about the primary mechanisms
by which carboxyhemoglobin formation exerts its toxic effects.
The remaining chapters consider adverse effects on health. A review
of the abundant findings from animal studies helps elucidate the mechanisms
of carbon monoxide toxicity, its direct effects on the blood and other
tissues, and the manifestations of these effects in the form of changes
in organ function. Studies of developmental toxicity provide strong
evidence that material exposure produces reductions in birth weight,
cardiomegaly, delays in behavioral development, and disruptions in cognitive
function.
A chapter on health effects in humans considers numerous investigations
of adverse effects linked to typical ambient exposure levels. Findings
are summarized in terms of damage to the cardiovascular and respiratory
systems, effects on neurobehavioral functions, developmental toxicity,
and other systemic effects. Also considered are the effects of exposure
at high altitudes, in users of psychoactive drugs, and in combination
with exposure to other air pollutants.
An evaluation of high-risk groups concludes that patients with reproducible
exercise-induced ischemia are a sensitive group at increased risk for
experiencitig adverse health effects. The report also found evidence
indicating that exposure may cause an increased risk of sudden death
from arrhythmia in patients with coronary artery disease. The report
further concludes that exposure during pregnancy and early childhood
carries a number of important risks.
Concerning accidental exposure to high concentrations, the report concludes
that carbon monoxide poisoning occurs frequently, has severe consequences
(including immediate death), involves complications and late sequelae,
and is often overlooked. Among its many other conclusions, the report
calls for better education of the general population about the risks
of exposure, especially in individuals with cardiovascular and respiratory
disease, and better awareness among medical professions of the dangers
of carbon monoxide exposure during pregnancy.