Tetrachloroethylene (Perc) Exposure and Visual Contrast Sensitivity (VCS) Test Performance in Adults and Children Residing in Buildings With or Without a Dry Cleaner

Information Sheet - April 2010


The New York State Department of Health's (NYSDOH) Center for Environmental Health conducted a study that investigated the relationship between exposure to tetrachloroethylene (perc) and measures of visual function (visual contrast sensitivity (VCS) and color vision) in adults and children. This study was funded by a grant from the United States Environmental Protection Agency with staff support from NYSDOH.


Perc is a solvent frequently used to dry clean garments and other textiles. When dry cleaners using perc are co-located in residential buildings, perc levels in indoor air of apartments in the buildings are sometimes elevated. NYSDOH is concerned about elevated indoor air perc levels because perc can have harmful effects, especially on brain function. The main objectives of this study were to determine perc exposures of residents in apartments in residential buildings with co-located dry cleaners; and, to see whether visual function of adult and child residents was affected when perc exposures were elevated.


Households in residential buildings (with and without a co-located dry cleaner using perc) in New York City with at least one adult and one school-age child, were enrolled in this study. Adults were 35–45 years old, and children were 9–11 years old. Perc exposures (indoor air, exhaled breath, and blood perc levels) and measures of visual function (VCS and color vision) were obtained for each participant and associations between all measures of perc exposure and visual function were assessed. The main body of this report describes associations between perc exposure and VCS observed in this study. Associations between perc exposure and color vision are summarized in an appendix of this report.

VCS is a measure of a person's ability to distinguish the contrast between a viewed object and its background, and to identify what the object is. Objects or images that contrast strongly against the surrounding background are easier to see. For example, it is easier to see a black cat on snow (a high contrast image) than a white cat on snow (a low contrast image). VCS is an important characteristic of a person's visual function because it indicates how well the eye can detect things and also how well the brain can identify what is detected.

The VCS test administered in this study assessed each participant's ability to detect five different images. The images are circles filled with parallel dark and light bars that vary from high to low contrast. The number of bars in each of the five circular images varies and is referred to as the spatial frequency. VCS for each participant's eye was tested separately and analyses of the effect of perc on VCS is based on participant's worse performing eyes.


Indoor air perc levels were significantly elevated in households in buildings with co-located dry cleaners. Based on their indoor air perc levels, participants were grouped into three groups as follows:

Participant Average Indoor Air Levels of Perc (mcg/m3)*
Building without a Dry Cleaner Building with a Dry Cleaner
perc less than 100 mcg/m3 perc greater than 100 mcg/m3
Adults 3 12 480
Children 3 12 340
* All values in micrograms per cubic meter of air

Perc exposure affected VCS differently in children and adults. Statistical analyses of relationships between perc exposures and VCS for worse performing eyes showed that increasing levels of perc exposure were associated with decreased children's VCS at a single spatial frequency, although their VCS was still within a normal range. Among adults VCS was not affected. No measure of perc exposure was significantly associated with decreased color vision performance among either adults or children.

The effect of perc on VCS was most noticeable in the small group of eleven children living in buildings with a co-located dry cleaner and where indoor air perc levels exceeded 100 mgc/m3. Indoor air perc levels in these children's apartments ranged from 127 to 710 mcg/m3 and averaged about 340 mcg/m3. These levels were about 100 times higher than levels found in buildings where there were no dry cleaners.


In this study elevated indoor air perc levels were associated with a slightly increased risk for children to have decreased VCS, although their VCS scores were still within a normal range. For affected children, the decrease was very small and occurred for only worse performing eyes in one of the five spatial frequencies. Therefore, the risk for decreased VCS scores among affected children is considered to be small.

The observed associations between elevated indoor air perc levels and children's VCS suggests that indoor air perc levels in the range detected may have subtle, or subclinical, effects on the brain. Additional research is needed to better understand the relationships between indoor air perc levels, and both VCS and brain function.

A Fact Sheet describing the NYSDOH perc guideline is available at www.health.ny.gov/environmental/chemicals/tetrachloroethene/.

Contact Us

If you have any questions or would like more information about this study, please contact:

Jan E. Storm, Ph.D.
NYS Department of Health
Center for Environmental Health
Bureau of Toxic Substances Assessment