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The information presented in the Remedial Investigation (RI) of the Celtor Chemical Works Site shows an increased excess life-time skin cancer risk (ELSCR) from ingestion of arsenic-laden soil. This ELSCR is compared to the ELSCR from ingestion of soil with arsenic at background concentrations. Mean and maximum soil copper concentrations exceed the California Assessment Manual (CAM) Total Threshold Limit Concentration (TTLC), constituting a hazardous waste by California law. Mean and maximum soil lead concentrations on the plant site exceed the CAM TTLC of 1000 mg/kg and the Centers for Disease Control (CDC) level of concern of 500-1000 ppm. From the information presented in the RI, ingestion of lead in soil by children would exceed the EPA Acceptable Daily Intake (ADI) for lead. Neither soil levels of cadmium, zinc, or iron nor surface water or groundwater metals levels were concluded to pose a human health risk. The U. S. Environmental Protection Agency (EPA), Region IX, approved a Record of Decision (ROD) on September 30, 1985, selecting excavation of contaminated soils to depths of 1 to 4 feet and disposal at an off-site RCRA-approved Class 1 hazardous waste disposal facility.

In accordance with ATSDR's mandate under the Superfund Amendments and Reauthorization Act (SARA) to perform a public health assessment of all National Priorities List sites, ATSDR has reviewed the RI/FS with which we were provided. The remedial alternative chosen in the ROD should adequately address the public health risks from ingestion of soil with hazardous levels of arsenic and lead by children. However, ATSDR has reservations about the following: (1) Whether the use of a cancer risk assessment model for arsenic ingestion, which has been revised by the EPA Risk Assessment Forum and Environmental Criteria Assessment Office, is significant with respect to the conclusion of a public health risk resulting from arsenic ingestion; and, (2) EPA's lack of a plan for followup sampling to ascertain the effectiveness of the remedial measures.


The Celtor Chemical Works is a 2.5-acre site which is located at the north end of the Hoopa Valley in Humboldt County, California. The Hoopa Valley Indian Tribe owns the land. The U.S. Bureau of Indian Affairs and the U. S. Department of the Interior hold the land in trust, and leased the site to the Celtor Chemical Corporation in 1957. The Celtor Chemical Corporation used the site for the reduction of sulfide ore from the nearby Copper Bluff Mine by dissolved air flotation to produce copper, zinc, and precious metals. The tailings ponds for the reduction works were located on a sandbar in the adjacent Trinity River. A bulldozer broke through one of the pond dikes causing uncontrolled discharge into the Trinity River in 1962, with reported fishkills. California Department of Fish and Game citations and apparent bankruptcy of the company in 1962 seemed to correlate with suspension of activity at the site.

The site consists of the plant, an adjacent pasture used for grazing livestock, a gully connecting the plant and the Trinity River, a drainage creek that collects surface run-off and carries it into the Trinity River, and a fishing access road that is heavily used by local residents. In July 1981, the California Department of Health Services (DOHS) identified the site in a statewide survey of abandoned industrial waste facilities and conducted extensive sampling, which showed elevated concentrations of metals in soils and a very acidic surface run-off. EPA conducted a Focused Feasibility Study and an Initial Remedial Measure (IRM). IRM activities included removal to a Class 1 hazardous waste landfill of tailings and ore piles and removal from the site of ore processing vats, wooden structures, concrete-surrounded waste vats, and other concrete structures. Also, the main portion of the site was fenced, and the access road was covered with gravel. The flow of several springs was diverted away from contaminated areas and into a nearby creek emptying into the Trinity River. Topsoil removal and replacement were conducted on the plant site and a portion of the pasture. Identification during the IRM of apparent waste materials on-site, beneath tailings piles, and in a gully north of the site led to the current RI and FS and the subsequent ROD to obtain a permanent remediation of the site.


  1. California DOHS, Celtor Chemical Works Soil Data, November, 1982.

  2. California DOHS, Celtor Chemical Works Soil Data, February, 1983.

  3. Centers for Disease Control (CDC), Center for Environmental Health (CEH), Superfund Implementation Group, Memorandum Re: Hoopa Valley Hazardous Waste Sites, California, January 1983.

  4. CDC, CEH, Superfund Implementation Group, Memorandum Re: Hoopa Valley Hazardous Waste Sites, California, January 1983.

  5. CH2M Hill, Remedial Investigation Report: Celtor Chemical Works Site, Hoopa, California, Contract No. 68-01-6692, April 1985.

  6. CH2M Hill, Final Feasibility Study Report: Celtor Chemical Works Site, Hoopa, California, Contract No. 68-01-6692, January 1986.

  7. Ecology and Environment, Inc., Field Investigations of Uncontrolled Hazardous Waste Sites--Analytical Results Hoopa Valley Sites, Hoopa, California, Contract No. 68-01-6056, February 1982.

  8. Greig, KL, Weston SPER, Memorandum Re: Celtor Chemical Works Air Sampling, July 1985.

  9. Schlag, RD, and JW Stratton, California DOHS, Epidemiological Studies Section, Environmental Toxics Epidemiology Unit, Memorandum Re: Response to Request for "Health Risk Analysis" of Celtor Chemical Works Site, March 1983.

  10. Schlag, RD, and JW Stratton, California DOHS, Epidemiological Studies Section, Environmental Toxics Epidemiology Unit, Memorandum Re: Celtor Chemical-- Health Assessment, August 1983.


The principal contaminants are arsenic, cadmium, copper, lead, iron, and zinc. Measured concentrations of these principal contaminants in water ranged from non-detectable to maxima in micrograms/1 of 50 (estimated) for arsenic, 241 for cadmium, 9,920 for copper, 45 for lead, 20,000 for iron, and 48,300 for zinc. Measured ranges of concentrations in mg/kg in soil were 6 to 600 for arsenic, non-detectable to 310 for cadmium, 26 to 124,000 for copper, non-detectable to 2,650 for lead, 13,600 to 337,000 for iron and 55 to 51,500 for zinc.


  1. Leaching of metals from contaminated soil into groundwater.

  2. Surface run-off carrying metals from contaminated soil.

  3. Direct disturbance of contaminated subsurface soil by digging or other land use activities.

  4. Generation of dust by wind from contaminated soil.


  1. Ingestion of soil or dust.

  2. Ingestion of surface water (i.e., run-off).

  3. Ingestion of groundwater.

  4. Inhalation of dust.


The Celtor Chemical Works Site, an NPL site, has contamination of soil with copper, zinc, arsenic, cadmium, lead, and iron. ATSDR has performed a public health assessment of this site in accordance with its mandate under SARA to determine and identify what public health risks, if any, are posed by this contamination.


The RI predicts an excess lifetime skin cancer risk (ELSCR) from ingestion of arsenic-laden soil on the plant site of 1x10-1 and in the pasture and gully of 4x10-3. Ingestion of soil containing background-level concentrations is shown to yield an ELSCR of 6x10-4 to 6x10-3. Therefore, the calculated ELSCR from ingestion of soils from the site was assessed by EPA to represent a public health risk. Maximum surface copper concentrations of 124,000 mg/kg on the plant site and 2,640 mg/kg in the gully, as well as the mean surface concentration of 6,240 mg/kg on the plant site exceed the CAM Total Threshold-Limit Concentration (TTLC) of 2,500 mg/kg; this constitutes a hazardous waste by California law. The maximum surface lead concentrations of 1,040 mg/kg on the plant site and 1,514 mg/kg in the pasture exceed the CAM TTLC of 1,000 mg/kg. (These concentrations also exceed the CDC level of concern for lead in soil of 500-1,000 ppm. This level of concern represents the soil concentration of lead at which children ingesting soil might be expected to experience adverse health effects.) Ingestion of soil by children would be predicted to exceed the EPA Acceptable Chronic Intake (AIC) for lead ingestion of 1.4x10-3 mg/kg/day. From the information provided, cadmium, iron, and zinc do not pose a human health risk at the Celtor Chemical Works Site.

The scenario which is considered in the RI to yield the maximal potential ingestion of arsenic in surface water is that of a swimmer in the Trinity River ingesting water which is draining from the creek and not yet diluted by the water of the Trinity River. Calculations show no ELSCR for ingestion of surface water during swimming at the confluence of the drainage creek and Trinity River. The RI states that, although surface water (run-off) concentrations of cadmium, copper, zinc, and iron exceed EPA's National Primary and Secondary Drinking Water Regulations, these metals were not assessed to pose a human health risk unless 2 liters or more of the run-off are ingested per day. The report states that the Hoopa Valley Reservation residents have a water system and do not ingest surface run-off or groundwater from the site. Presumably, the water system transports water from a source external to the site; however, if this is the case, the point would be more clearly made if this were stated explicitly in the report. If the residents, in fact, consume water from a source external to the site, ingestion of surface water or groundwater are not considered to present a problem. The information in the RI shows no significant contamination of groundwater. Finally, the FS states that drainage creek discharge into the Trinity River does not violate the EPA One-Hour National Ambient Water Quality Criteria for Protection of Freshwater Aquatic Life (WQCAL) for any of the principal contaminants after dilution of the creek discharge by the Trinity River even at short distances from the point of discharge. (It should be noted that there is no One-Hour WQCAL for iron.)

The Risk Assessment Forum and the Environmental Criteria Assessment Office of EPA have recently revised the risk assessment model for the ingestion of arsenic because of basic flaws in the study of Tseng et al. (1968), which provided the dose-response relationship upon which this risk assessment model is based. ATSDR has reservations about the use of a fundamentally erroneous risk assessment model, which has already been revised by the Risk Assessment Forum, to make assessments of the public health risk from the ingestion of arsenic at this site.

EPA's ROD identified the selected remedial alternative for the Celtor Chemical Works Site to be excavation of the contaminated soils to depths of 1 to 4 feet and disposal at an off-site RCRA-approved Class 1 hazardous waste facility. The FS assesses this alternative to reduce maximally "risks to the public health and welfare, or to the environment." Additionally, the FS states that, "After completion of the remediation measures, no environ-mental sampling or testing would be required." The report states that soil contamination was determined to extend to depths of 3 feet. These measures will presumably remove all of the contamination in soil; however, EPA apparently plans no follow-up monitoring or sampling to ascertain the adequacy of the remediation.

It may seem obvious that removal of all soils on the site to depths at which contaminant concentrations have been found would eliminate any public health risks from children ingesting soils with hazardous levels of lead and arsenic. This planned remediation would also seem to remove any potential future public health risks from bioaccumulation of toxicants in plants and grazing cattle or bioaccumulation of toxicants in fish secondary to toxicants being carried in surface run-off. However, such an assumption must not be made without demonstration, particularly in a system as complex and multi-variant as a hazardous waste site. It would be best to demonstrate elimination of the public health hazard by followup measurements; therefore, we have reservations about EPA's lack of a plan for followup sampling and that the statement in the FS that such sampling would not be necessary.


  1. Assuming that the use of a risk assessment model for ingestion of arsenic, which has been revised by EPA's Risk Assessment Forum and Environmental Criteria Assessment Office, does not affect the validity of the conclusion of an ELSCR from ingestion of arsenic at the Celtor Chemical Works Site, we can conclude that a public health risk exists at the site. Furthermore, the soil lead levels which are in excess of the CAM TTLC and CDC levels of concern would be anticipated to yield ingestion by children in excess of EPA's AIC for lead and are public health risks.

  2. The alternative selected in the ROD, removal of contaminated soils to depths of 1 to 4 feet and disposal at an off-site RCRA-approved Class 1 hazardous waste facility, seems adequate to eliminate the public health risks at the site. However, the effectiveness of these measures in eliminating the public health risks should be verified by follow-up sampling after the remediation.

Leslie J. Hutchinson, M.D.


Henry Longest
George Buynoski

ATSDR:OHA:HACA:LJHutchinson:cs 5/13/87


Heydorn, K., "Environmental Variation of Arsenic Levels in Human Blood Determined by Neutro-activation Analysis," Clinical Chim. Acta, 1970 28:349-357.

ICF Incorporated (prepared for EPA Office of Emergency and Remedial Response), Draft Superfund Public Health Evaluation Manual, December 1985 (unpublished document).

National Academy of Sciences, Committee on Medical and Biological Effects of Environmental Pollutants, Division of Medical Sciences, Assembly of Life Sciences, National Research Council, Arsenic, 1977, Washington, D.C.

Southwick, J.W., A.E. Western, M.M. Beck, T. Whitley, R. Isaacs, J. Petajan, and C.D. Hansen, "An Epidemiological Study of Arsenic in Drinking Water in Millard County, Utah," In: Lederer, W.H. and R.J. Fensterheim, eds., Arsenic: Industrial, Biomedical, Environmental Perspectives, 1983, Van Nostrand Reinhold Co., New York.

Tseng, W.P., H.M. Chu, S.W. How, J.M. Fong, C.S. Lin, and S. Yeh, "Prevalence of Skin Cancer in an Endemic Area of Chronic Arsenicism in Taiwan," Journal of the National Cancer Institute, 1968, 40:453-463.

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