Monday, November 14, 2005

Carcinogens in the Neighborhood - Public Health Works, but does it work enough?

Probably the big 4 for scrutinized environmental chemical hazards are airborne particles, metals, POP's, and, mentioned here, volatile chlorinated hydrocarbons. Lately, particles have taken the lead for most evidence for adverse effects at prevailing levels.

{BrooklynDodger also worries about volatile aliphatic hydrocarbons [gasolene, diesel fuel, etc], but laboratory evidence for carcinogenicity is now ignored by the EPA embrace of the Houdini risk assessment alpha-2 microglobulin hypothesis.}

Small sources are an issue for population exposure. The sweet smell in the dry cleaner is perchlorotheylene [tetrachloroethylene]. Drycleaning consists of running your stuff through washing machines which use perc instead of water, and then dryers which aim to condense the perc so it can be reused. The gunk on your clothes are removed from the wash perc by running through column like a liquid chromatography column. The Dodger thinks the condensation is pretty efficient, so the sweet smell is fugitive emissions from wet clothing. New equipment is dry to dry, washing and drying in the same machine. Your neighborhood cleaner likely has a few 55 gallon drums of perc around too.

Anyway, back to this post. Perc is carcinogenic in the 100 ppm inhalation range [see below]. Houdinists dispute the "relevance" of all these tumors to people. The rat leukemias are time dependent. The male rat kidney has generally been erased [not sure why these are called "rare" male rat kidney tumors] by alpha-2. Houdinists generally discount any mouse liver tumors, although hepatocellular carcinomas in female mice are harder to discount. Perc didn't cause lung tumors in the mice, which is a common outcome for volatile organics; mouse lung tumors are erasable by the mouse clara cell hypothesis. Perc was not genotoxic in multiple systems. [These assays don't discount gene silencing mechanisms.] The 100 ppm effect range is relatively more potent than other volatile organics. [The Dodger lazes today, and hasn't gone back to the pathology tables in the bioassay report to eyeball the NOAEL level; EPA IRIS should go 1000 fold below; for occupational the Dodger would use 100 fold below as a point of departure.]

[Epidemiology in dry cleaners is mixed. NTP, quoting IARC, notes " Although these studies suggest a possible association between long-term
occupational exposure to tetrachloroethylene and increased lymphatic
malignancies and urogenital cancers, the evidence must be regarded as
inconclusive because workers were exposed to petroleum solvents and
other dry cleaning agents as well as tetrachloroethylene. When all
studies are considered, there is evidence for consistent positive
associations between tetrachloroethylene exposure and esophageal and
cervical cancer and non-Hodgkin’s lymphoma. While these
associations appear unlikely to be due to chance, confounding cannot
be excluded; further, the total numbers in the cohort studies combined
are relatively small (IARC 1995)."

NTP further quotes "
Typical tetrachloroethylene concentrations in
workplace air at dry cleaning facilities were 350 to 700 mg/m3 (about
50 to 100 ppm) in the 1970s and 70 to 350 mg/m3 (about 10 to 50
ppm) in the 1980s (IARC 1995). The highest exposures occur when
loading and unloading the dry cleaning machines;"

The OSHA PEL for perc is 100 ppm. The ACGIH TLV for perc is 25 ppm. Obviously no margins here, for a carcinogen.

Coming back to the environmental study. The conversion from ppm to mg/M3 for perc is 6.78. The 100 ug/M3 residential guideline cited below converts to 14 ppb. The 14 ppb ball parks to 10,000 fold below the 100 ppm effect level.

The study below notes a mean exposure of 34 ug/M3, 17/65 apartments exceeding the limit. BrooklynDodger would have preferred the the authors, reviewers and editors have insisted on the median going into the abstract. The median, or geometric mean states the central tendency of distributions of environmental measurements better than the mean. The mean exposure of the population - the best measure of dose absorbed - is best estimated by calculation from the geometric mean and dispersion.

This paper demonstrated a 10 fold reduction in exposure since NYC started to pay attention to this exposure. That's a validation of public health intervention.

Environmental Health Perspectives Volume 113, Number 10, October 2005

Tetrachloroethylene (PCE, Perc) Levels in Residential Dry Cleaner Buildings in Diverse Communities in New York City

Michael J. McDermott,1 Kimberly A. Mazor,1 Stephen J. Shost,1 Rajinder S. Narang,2 Kenneth M. Aldous,2 and Jan E. Storm1

1Center for Environmental Health, New York State Department of Health, Troy, New York, USA; 2Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany, New York, USA

Fugitive tetrachloroethylene (PCE, perc) emissions from dry cleaners operating in apartment buildings can contaminate residential indoor air. In 1997, New York State and New York City adopted regulations to reduce and contain perc emissions from dry cleaners located in residential and other buildings. As part of a New York State Department of Health (NYSDOH) study, indoor air perc levels were determined in 65 apartments located in 24 buildings in New York City where dry cleaners used perc on site. Sampling occurred during 2001-2003, and sampled buildings were dispersed across minority and nonminority as well as low-income and higher income neighborhoods. For the entire study area, the mean apartment perc level was 34 µg/m3, 10-fold lower than mean apartment levels of 340-360 µg/m3 documented before 1997. The maximum detected perc level was 5,000 µg/m3, 5-fold lower than the maximum of 25,000 µg/m3 documented before 1997. Despite these accomplishments, perc levels in 17 sampled apartments still exceeded the NYSDOH residential air guideline of 100 µg/m3, and perc levels in 4 sampled apartments exceeded 1,000 µg/m3. Moreover, mean indoor air perc levels in minority neighborhoods (75 µg/m3) were four times higher than in nonminority households (19 µg/m3) and were > 10 times higher in low-income neighborhoods (256 µg/m3) than in higher income neighborhoods (23 µg/m3). Logistic regression suitable for clustered data (apartments within buildings) indicated that perc levels on floors 1-4 were significantly more likely to exceed 100 µg/m3 in buildings located in minority neighborhoods (odds ratio = 6.7; 95% confidence interval, 1.5-30.5) than in nonminority neighborhoods. Factors that may be contributing to the elevated perc levels detected, especially in minority and low-income neighborhoods, are being explored.
Environ Health Perspect 113: 1336-1343 (2005).


Toxicology and carcinogenesis studies of tetrachloroethylene (perchloroerhylene) in F344/N rats and B6C3F1 mice (inhalation studies)
NTP Working Group
National Toxicology Program Technical Report Series Vol:311 (1986) 197 p

Toxicology and carcinogenesis studies of tetrachloroethylene (99% pure) were conducted by inhalation exposure of groups of 50 male and 50 female F344/N rats and B6C3F1 mice 6 hours per day, 5 days per week, for 103 weeks. The exposure concentrations used (0, 200, or 400 ppm for rats and 0, 100, or 200 ppm for mice) were selected on the basis of results from 13-week inhalation studies...

Tetrachloroethylene was not mutagenic in salmonella typhimurium strains TA98, TA100, TA1535, or TA1537 in the presence or absence of male Syrian hamster or male Sprague-Dawley rat liver S9. Tetrachloroethylene was not mutagenic in L5178Y/TK mouse lymphoma cells with or without metabolic activation and did not induce sex-linked recessive lethal mutations in drosophila melanogaster. Tetrachloroethylene did not induce sister-chromatid exchanges or chromosomal aberrations in Chinese hamster ovary cells in the presence or absence of metabolic activation;

Under the conditions of these 2-year inhalation studies, there was clear evidence of carcinogenicity of tetrachloroethylene for male F344/N rats as shown by an increased incidence of mononuclear cell leukemia and uncommon renal tubular cell neoplasms. There was some evidence of carcinogenicity of tetrachloroethylene for female F344/N rats as shown by increased incidences of mononuclear cell leukemia. There was clear evidence of carcinogenicity for B6C3F1 mice as shown by increased incidences of both hepatocellular adenomas and carcinomas in males and of hepatocellular carcinomas in female

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