Reviews
The Developing Brain and Endocrine Disruption
Many environmental contaminants and degradation products can interfere with the
thyroid system. Many of these compounds cross the placental and brain barriers
and can affect development, depending on the time and duration of exposure.
Colborn (p. 944) explores the possibility that thyroid-disrupting contaminants
contribute in part to the increasing prevalence of attention deficit hyperactivity
disorder, autism, and neurodevelopment problems. Links have been identified
between exposure to specific chemicals or chemical classes and developmental
difficulties in laboratory animals, wildlife, and humans.
Pesticide Neurotoxicity
Poisoning by acute high-level exposure to certain pesticides has well-known neurotoxic
effects, but whether chronic exposure to moderate levels of pesticides is also
neurotoxic is more controversial. Kamel and
Hoppin (p. 950) review studies
of moderate pesticide exposure and find increased prevalence of neurologic
symptoms and changes in neurobehavioral performance that reflect cognitive
and psychomotor dysfunction. However, there are many information gaps. It is
possible that the most sensitive manifestation of pesticide neurotoxicity is
a general malaise lacking in specificity and related to mild cognitive dysfunction.
Exposure to PCDD/Fs through Sewage Sludge Recycling
Sewage sludge from municipal wastewater treatment is used in agriculture
as a nutrient source and to aid in moisture retention. Rideout and Teschke
(p. 959) review the published empirical data from international sources to
examine the potential impact of sludge-amended soil on exposures to polychlorinated
dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) from plant and
animal foods. Currently available data suggest that sewage sludge application
to land used for most crops would not increase human exposure. However, the
use of sludge on land used to graze animals appears likely to result in increased
human PCDD/F exposure.
Lung Cancer and PAH Meta-Analysis
Typical polycyclic aromatic hydrocarbon (PAH) mixtures are established lung
carcinogens, but the quantitative exposureresponse relationship is less
clear. Armstrong et al. (p. 970) provide a review and meta-analysis of published
occupational epidemiologic studies. The average estimated unit relative risk
(URR) at 100 µg/m3 years benzo[a]pyrene was 1.20 (95% confidence
interval, 1.111.29) and was not sensitive to particular studies or analytic
method. However, the URR varied by industry. These results provide a more secure
basis for risk assessment than was previously available.
New
Generation of Coastal Indicators
Half the world's human population live within 100 km of a coastline. Consequently,
coastal ecosystems are at serious risk. Niemi et al. (p. 979) review recent
developments in ecologic indicators and emphasize the need for improvements
in understanding stressresponse relationships, contributions of multiple
stressors, assessments over different spatial and temporal scales, and reference
conditions. New indicators are essential to measure the condition of coastal
resources, to diagnose stressors, and to protect human health and the quality
of the coastal environment.
Low-Level Lead Exposure and
Children's IQ
A recent study of children whose lifetime peak blood lead levels were consistently
below 10 µg/dL has extended the association of blood lead and intellectual
impairment to lower levels. Koller et al. (p. 987) review recent developments
of low-level lead exposure and children's cognitive development and conclude
that efforts should continue to reduce childhood exposure. However, exposure
to lead should be seen within the many other risk factors affecting on
Health and Environmental Information Systems
Thousands
of new chemicals that might have toxic properties constituting potential health
hazards are added to the environment each year. Exposures of humans and the
environment are typically unevenly distributed spatially and temporally. Disease
occurrences also show geographically varying patterns. Rapid risk assessment
is therefore essential in protecting from harmful exposures. The Mini-Monograph
(p. 995) on health and environmental information systems presents advances
in geographic information systems, statistical methodology, and availability
of high-resolution, geographically referenced health and environmental quality
data. These approaches have created unprecedented new opportunities to investigate
factors in explaining local geographic variations. They also present new challenges.
[Table of Contents]
Last Updated: June 8, 2004
|