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    This Public Health Assessment was prepared and reviewed by:

Theresa Kilgus, Lead Health Assessor
Agency for Toxic Substances and Disease Registry
Division of Health Assessment and Consultation
Exposure Investigation and Consultation Branch

Susan Moore, Toxicologist
Agency for Toxic Substances and Disease Registry
Division of Health Assessment and Consultation
Exposure Investigation and Consultation Branch

Richard Kauffman, Regional Representative
Agency for Toxic Substances and Disease Registry
Office of Regional Operations, Region

Marie Patterson, Community Involvement Specialist
Agency for Toxic Substances and Disease Registry
Division of Health Assessment and Consultation
Community Involvement Branch

Dianne Drew, Health Educator
Agency for Toxic Substances and Disease Registry
Division of Health Education and Prevention


Safe Drinking Water Act
ATSDR Methods Summary

Safe Drinking Water Act

The municipal water system in Sitka is regulated under the Safe Drinking Water Act (SDWA). The purpose of the SDWA is to protect the public from contaminated drinking water. The SDWA requires EPA to identify contaminants in drinking water which may have an adverse effect on people's health and to specify a maximum contaminant level (MCL) for those contaminants where feasible [1]. The MCL is the National Primary Drinking Water Standard. Dioxin is one of the 83 contaminants that are required to be regulated. However, the City of Sitka has a state-wide waiver that is approved by EPA. The EPA's MCL for dioxin is 30 ppt. These standards are to be met by all public water systems. The SDWA also requires EPA to set standards for filtration and disinfection of drinking water. The National Primary Drinking Water Regulations require systems relying on surface waters like Blue Lake to use disinfection and to use filtration unless stringent standards are met for microbiological contaminants, turbidity, and protection of surface water used by the system [2]. To avoid filtration the Sitka municipal water system must [1] :

1) use disinfection and provide redundant disinfection capacity or an automatic shut-off if residual disinfectant levels drop to low;
2) must maintain disinfectant levels and operating conditions sufficient to inactivate 99.9% of Giardia lamblia cysts and 99.99% of viruses [3];
3) establish and maintain an affective watershed control program;
4) verify the watershed and disinfectant programs through annual state inspections;
5) prevent any outbreaks of waterborne disease; and
6) comply with total coliform and trihalomethane MCLs.

The watershed control program must 1) characterize the watershed hydrology and landownership; 2) identify watershed characteristics and activities which may have an adverse effecton source water quality; and 3) monitor the occurrence of activities which may have an adverseeffect on source water quality [4].

To ensure these requirements are met, an annual on-site inspection of the City of Sitka's publicwater system is conducted by a consultant certified by the State of Alaska. Up to this time, thewater system has met all requirements [5].


  1. Randle, RV. Chapter 4, Safe Drinking Water Act in Environmental Law Handbook, 11thEdition. Government Institutes, Inc. 1991, Rockville, Maryland.

  2. Williams, SE. Chapter 7, Safe Drinking Water Act in Environmental Law Handbook,13th edition, editor Thomas F.P. Sullivan, Government Institutes, Inc. 1995, Rockville,Maryland.

  3. 18ACC 80.532. Disinfection requirements for systems avoiding filtration.

  4. City and Borough of Sitka, Alaska Public Works Department Water Division. WatershedControl Program, Blue Lake Drinking Water Supply. Submitted as part of the AvoidanceCriteria of the U.S. Environmental Protection Agency Surface Water Treatment Rule 40C.F.R 141.71 Safe Drinking Water Act. June 1992.

  5. City and Borough of Sitka. Report on 1997 Annual onsite Inspection of City of Sitka Public Water System To Satisfy Annual Report Requirements for Avoidance of Filtration. December 1, 1997.

ATSDR Methods Summary

Toxic Equivalency Factors(TEFs) and Toxic Equivalents (TEQs)
Toxic Equivalency Factors (TEFs) were developed by EPA and have been used by regulatoryagencies world-wide to estimate the potential health effects of exposure to dioxin like chemicals.TEFs were derived from subchronic studies in mice using enzyme induction as an endpoint.These values will be used to predict the relative potency of mixtures of these chemicals to induceimmune suppression, oxidative stress and enzyme induction in mice and enzyme induction,thyroid hormone alterations and reproductive and developmental toxicity in rats.

The number and arrangement of the chlorine substituents determines the toxicity of dioxincongeners. The toxicity of individual congeners varies 1000-fold, which complicates the riskassessment of these compounds when found in the environment. A further complication is thatdioxins are present along with dibenzo furans, polychlorinated biphenyls, and other halogenatedaromatic compounds in complex mixtures.

To simplify the task of assessing the risk resulting from exposure to complex mixtures of dioxinsand related compounds, Toxic Equivalency Factors (TEFs) were developed. TEFs are measuresof toxicity determined relative to 2,3,7, 8-TCDD, which is given a TEF of 1.0. The 7 most toxicdioxins congeners, and the ten most toxic dibenzofuran congeners, have been assigned TEFvalues ranging from 0.5 to 0.001. The remaining 193 dioxins and dibenzofurans are less toxicand are thought to contribute comparatively little to the toxicity of a complex mixture. Theyhave been assigned a TEF value of 0. When isomer-specific data are available, the concentrationof each dioxin and dibenzofuran congener containing the 2,3,7, 8-substitution pattern ismultiplied by its respective TEF, and the products are summed to generate a single value calledthe "2,3,7, 8-TCDD Toxic Equivalent (TEQ)". A review of environmental and mechanisticconsideration which support the development of TEFs has recently been published.

While many research groups have utilized TEF approaches, the World Health Organizationsuggests that "the use of [2, 3, 7, 8] TCDD equivalents must be regarded as an interim procedurefor the measurement of the toxicity of environmental samples, in the absence of long-termtoxicity data on specific PCDD [polychlorinated dibenzo-p-dioxin] isomers and mixtures of thesecompounds." Because of the many gaps in the data at present, the use of TEFs is considered tobe imprecise, but the best that is available to date.


Occurring over a long period of time (more than one year).

Comparison Values
Estimated contaminant concentrations in specific media that are not likely to cause adverse health effects, given a standard daily ingestion rate and standard body weight. The comparison values are calculated from the scientific literature available on exposure and health effects. Please refer to Appendix E for further information on comparison values.

The amount of one substance dissolved or contained in a given amount of another. For example, sea water contains a higher concentration of salt than fresh water.

Any substance or material that enters a system (the environment, human body, food, etc.) where it is not normally found.

Contact with a chemical by swallowing, by breathing, or by direct contact (such as through the skin or eyes). Exposure may be short term (acute) or long term (chronic).

Swallowing (such as eating or drinking). Chemicals can get in or on food, drink, utensils, cigarettes, or hands where they can be ingested. After ingestion, chemicals can be absorbed into the blood and distributed throughout the body.

Soil, water, air, plants, animals, or any other parts of the environment that can contain contaminants.

Minimum Risk Level (MRL)
An estimate of daily human exposure to a chemical that is likely to be without an appreciable risk of deleterious effects (noncarcinogenic) over a specified duration of exposure. Thus, MRLs provide a measure of the toxicity of the chemical.

Petitioned Public Health Assessment
A public health assessment conducted at the request of a member of the public. When a petition is received, a team of environmental and health scientists is assigned to gather information to ascertain, using standard public health criteria, whether there is a reasonable basis for conducting a public health assessment. Once ATSDR confirms that a public health assessment is needed, the petitioned health assessment process is essentially the same as the public health assessment process.

Public Comment
An opportunity for the general public to comment on Agency findings or proposed activities. The public health assessment process, for example, includes the opportunity for public comment as the last step in the draft phase. The purposes of this activity are to : (1) provide the public, particularly the community associated with a site, the opportunity to comment on the public health findings contained in the public health assessment; (2) evaluate whether the community health concerns have been adequately addressed; and (3) provide ATSDR with additional information.

Public Health Action
Designed to prevent exposures and/or to mitigate or prevent adverse health effects in populations living near hazardous waste sites or releases. Public health actions can be identified from information developed in public health advisories, public health assessments, and health consultations. These actions include recommending the dissociation (separation) of individuals from exposures (for example, by providing an alternative water supply), conducting biologic indicators of exposure studies to assess exposure, and providing health education for health care providers and community members.

In risk assessment, the probability that something will cause injury, combined with the potential severity of that injury.

Route of Exposure
The way in which a person may contact a chemical substance. For example, drinking (ingestion) and bathing (skin contact) are two different routes of exposure to contaminants that may be found in water.

Safe Drinking Water Act
The Safe Drinking Water Act was passed in 1974 following public concern over findings of harmful chemicals in drinking water supplies. The law established the basic Federal-State partnership for drinking water used today. It focuses on ensuring safe water from public water supplies and on protecting the nations aquifers from contamination.

Total Suspended Solids (TSS)
A measure of the suspended solids in wastewater, effluent, or water bodies, determined by tests for "total suspended non-filterable solids." (See: suspended solids.) Total Suspended Particles (TSP): A method of monitoring airborne particulate matter by total weight.

Toxicological Profile
A document about a specific substance in which ATSDR scientists interpret all known information on the substance and specify the levels at which people may be harmed if exposed. The toxicological profile also identifies significant gaps in knowledge of the substance, and serves to initiate further research, where needed.

1. Haziness in air caused by the presence of particles and pollutants. 2. A cloudy condition in water due to suspended silt or organic matter.

Reference for Glossary:

APPENDIX B - List of Figures & Tables


Figure 1: Blue Lake Vicinity Map
Figure 2: Alaska Pulp Company Intro Map
Figure 3: Blue Lake Topographical Map
Figure 4: Blue Lake Water Supply Overall System Schematic
Figure 5: Sediment Sampling Locations for Blue Lake
Figure 6: Dioxin Furan Results for Sediment Samples [1]


Table 1: Turbidity in City of Sitka Water Supply 1992-1996

Figure 1. Blue Lake Vicinity Map

Figure 2. Alaska Pulp Company Intro Map

Figure 3. Blue Lake Topographical Map

Figure 4. Blue Lake Water Supply Overall System Schematic

Figure 5. Sediment Sampling Locations for Blue Lake

Figure 6. Dioxin Furan Results for Sediment Samples

Table 1.

Turbidity in City of Sitka Water Supply, 1992-1996a
  1992 1993 1994 1995 1996
Jan 2.0/1.0 0.4/0.2 8.4/3.1 0.56/0.37 0.4/0.22
Feb 1.2/0.5 0.8/0.3 3.3/2.3 1.14/0.4 1.28/0.19
Mar 1.1/0.6 0.5/0.3 1.9/2.0 0.98/0.4 1.2/0.41
Apr 0.7/0.5 0.6/0.3 1.5/0.9 0.91/0.54 2.2/0.9
May 0.9/0.6 0.6/0.3 0.5/0.4 1.3/0.63 1.7/0.4
Jun 0.7/0.5 0.6/0.3 ND 0.9/0.47 2.12/0.3
Jul 1.2/0.4 0.3/0.2 0.6/0.3 0.4/0.22 4.8/0.38
Aug 1.6/0.5 0.5/0.3 0.6/0.3 2.57/0.35 1.4/0.6
Sept 1.2/0.4 10.0/0.4 43.0/0.6 0.61/0.44 18.0/0.6
Oct 1.2/0.5 10.0/4.1 8.0/2.0 0.88/0.32 17.0/4.16
Nov 1.1/0.5 45.0/2.7 2.4/1.0 0.3/0.22 3.31/1.2
Dec 1.7/0.3 12.8/6.1 1.2/0.7 0.4/0.24 3.49/1.2
a Turbidity is shown as the hi/low for the month.

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