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Visual contrast sensitivity deficits in Bohemian children
H K Hudnell1, I Skalik, D Otto
1National Health and Environmental Effects Research Laboratory, U.S. EPA, RTP, NC 27711, USA.
Neurotoxicology
|October 1, 1996
Summary
Visual contrast sensitivity (VCS) testing revealed deficits in learning-disabled children and those exposed to air pollution. While mercury levels correlated with VCS deficits, results suggest developmental delays rather than current toxicity in children.
Area of Science:
- Environmental Health
- Neuroscience
- Ophthalmology
Background:
- Visual contrast sensitivity (VCS) testing is a validated tool for medical diagnosis and detecting subclinical neurotoxicity.
- Previous research hypothesized that in utero exposure to combustion pollutants disrupts neurological development.
- Air pollution from soft-brown coal combustion contains pollutants such as mercury (Hg), arsenic (As), sulfur dioxide (SO2), nitrogen oxides (NOx), and aromatic hydrocarbons.
Purpose of the Study:
- To investigate visual contrast sensitivity (VCS) in children exposed to different environmental conditions.
- To compare VCS in children attending standard schools versus those in schools for the learning disabled.
- To assess the relationship between environmental pollutant exposure (Hg, As) and VCS in children.
Main Methods:
- Three studies were conducted in the Czech Republic involving 74 to 426 children.
- Visual contrast sensitivity (VCS) was measured using sinusoidal gratings at five spatial frequencies.
- Hair samples were analyzed for mercury (Hg) and arsenic (As) content in Studies 2 and 3.
Main Results:
- Children in schools for the learning disabled showed significantly lower VCS compared to controls, with normal visual acuity.
- Children in a high air pollution area (Teplice) exhibited VCS deficits at low to mid-spatial frequencies, with no correlation to arsenic levels.
- A significant negative correlation was found between hair mercury levels and VCS in the exposed district, though higher mercury levels were found in a less polluted area (Prachatice).
Conclusions:
- Behavioral VCS testing is practical for field studies involving young children, including non-English speakers.
- VCS deficits may indicate compromised vision in learning-disabled children and potential developmental delays related to prenatal pollutant exposure.
- Current mercury body burden may not be a reliable predictor of VCS deficits, necessitating longitudinal studies to clarify developmental impacts.