PCB Exposure May Come from Home, Not Just from Diet

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By Todd Neale, Staff Writer, MedPage Today

Published: January 18, 2008

Reviewed by Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine,

Harvard Medical School, Boston. Earn CME/CE credit for reading medical news

NEWTON, Mass., Jan. 18 -- Half-century-old wood finishes may be a source of

exposure to the banned pollutants polychlorinated biphenyls (PCBs) in the home,

researchers found. Action Points

Explain to interested patients that this case study of two homes in

Massachusetts suggests that wood finishes from the 1950s and 1960s may be a

source of

PCB exposure.

Also explain that PCBs are considered neurotoxins in humans and are

associated with certain cancers, including breast cancer.

Point out that the researchers did not confirm the source of the PCBs to

avoid regulatory and reporting difficulties for the residents.

Although dietary sources often take the blame, data from a case study here

suggest that environmental elements -- like dust -- may be greater contributors

to overall exposure for some people, reported Ruthann Rudel, M.S., of the

Silent Spring Institute here, and colleagues online in Environmental Health.

PCBs were found in building materials, including caulk, paint, and electrical

equipment, until banned for most uses in 1977. They are recognized as

developmental neurotoxins in humans, and are " also associated with thyroid

toxicity,

effects on immune, reproductive, nervous, and endocrine systems, and cancer

effects including breast cancer, " the researchers said.

The pollutants persist in the food chain, and several studies have concluded

that diet is a significant contributor to exposure, they said. These studies,

however, never looked at alternate sources.

To explore possible exposures besides diet, the researchers revisited a 2003

environmental exposure study of 120 homes on Cape Cod in Massachusetts.

In the earlier study, PCBs -- measured by the sum of the concentrations of

three types of the pollutants, congeners 52, 105, and 153 -- were detected in

the air in 38 (32%) of the homes and in dust in 22 (18%) of them.

In the new study, the researchers retested two houses with much higher PCB

concentrations compared with the rest of the study sample. They also measured

the residents' blood concentration levels, and sought possible sources of

exposure. The residents were interviewed about activities on the property that

may

have contributed to the high levels.

The researchers collected air samples in each house over 24 hours by drawing

air through a personal pesticide sampling cartridge. Dust samples were

collected using a modified vacuum cleaner.

Within one month of air sampling, blood samples from two residents from each

home (three women and one man) were analyzed for the presence of 33 PCB

congeners.

Rudel and colleagues found that PCB levels remained high in the air and dust

in the two homes.

The sum of the concentrations of PCBs 52, 105, and 153 in the air ranged from

8 to 35 ng/m3. A previous unrelated study had measured background PCB levels

of these three congeners, representing about 9% of total levels, at a maximum

of 7.3 ng/m3.

The EPA health-based screening value is 3.4 ng/m3 and it is likely that

levels in the two homes are 10 times higher, the researchers said.

The sum of the concentrations of PCBs 52, 105, and 153 ranged from 21 to 190

mg/g of house dust. A previous study measured a maximum value of 0.6 mg/g,

with these three PCBs making up 12% of the total value.

The EPA has not established a health-based screening value for PCBs in house

dust but a comparison can be drawn with the value for residential soil, 0.22

mg/g total, the researchers said, because " exposure assumptions for house dust

and residential soil are generally similar in EPA risk assessments. "

The PCB concentrations in the two homes exceeded this value by a factor of 95

to 860, the researchers said.

Residents' blood concentrations of PCBs were higher than levels found in the

National Health and Nutrition Examination Survey. Comparing results for the

sum of 10 types of PCBs, three of four residents in the Cape Cod study exceeded

the 95th percentile of the NHANES study.

One resident's blood concentration exceeded the maximum in NHANES (1,520

versus 1,466 ng/g lipid).

Another resident had a value (179 ng/g lipid) below the median NHANES value

(267 ng/g lipid), but had lived in the house for less than six months -- the

other three residents had lived in their homes for at least 10 years.

During interviews and surveys to identify possible sources for the PCBs, one

resident recalled using a hardwood floor finish called Fabulon in the 1950s

and 1960s. The researchers discovered in a 1957 reference book that this product

contained three types of PCBs at that time. By 1969, the product no longer

contained the pollutants.

One week before air and dust sampling began in this home, the Fabulon-coated

floor had been sanded and refinished, releasing a large amount of dust. This

likely accounted for the high PCB values in this home, the researchers said.

They did not confirm that the finishes on the wood floors in the two houses

were responsible for the high exposures. " Such a confirmation could create

regulatory and disclosure obligations that pose significant challenges to

individual homeowners, " the researchers said.

They concluded, however, that it is unlikely that the blood concentrations of

PCBs could be coming from diet alone. The three long-time residents had

congener profiles more like individuals who are occupationally exposed than did

the

one who moved in more recently, they said.

" These findings suggest that the exposure potential posed by historic use of

PCBs in building materials may be significantly underestimated, " they said.

The study was supported by the Hurricane Voices Breast Cancer Foundation, an

appropriation of the Massachusetts Legislature administered by the

Massachusetts Department of Health, and grants from the National Institute of

Environmental Health Sciences and the National Science Foundation.

The authors reported that they have no competing financial interests.

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