HEALTH CONSULTATION
KITSAP COUNTY - BAINBRIDGE ISLAND DUMP
BAINBRIDGE, KITSAP COUNTY, WASHINGTON
APPENDIX A: EXPOSURE ASSUMPTIONS
For this health consultation, it is assumed that a completed exposure pathway exists and residents were exposed 350 days per year, for thirty years to the maximum detected chemical concentrations which exceeded a screening value (i.e., those contaminants highlighted in Table 1). This exposure duration accounts for potential past and future exposures, as well as current exposure. Both adult and child through adult exposure scenarios were evaluated. Adults were assumed to consume 2 liters of water per day, and children were assumed to consume 1 liter of water per day until 5 years of age and 2 liters of water per day for the remaining 25 years. Children were assumed to be exposed for 5 years at a 16 kilogram (kg) body weight, for 10 years at a 40 kg body weight, and for 15 years at a 70 kg body weight. Children and adults were assumed to be exposed to VOCs through ingestion (drinking) and non-ingestion (inhalation and dermal contact) routes. Non-ingestion exposures are assumed to occur during household activities such as cooking, bathing, and dishwashing.
It is assumed that non-ingestion (inhalation and dermal) exposures are equal to exposures through ingestion.
Exposure dose = ((C x IR x EF x ED)/BW x AT)) x 2
Excess cancer risk = Exposure dose x CSF
where:
C = concentration of contaminant (µg/l)
IR = Ingestion rate (liters of water/day)
EF = Exposure frequency (days/year)
ED = exposure duration (total # of years in exposure period)
BW = body weight
AT = averaging time (70 years x 365 days/year)
CSF = Cancer slope factor (Estimates the excess upperbound lifetime probability
of an individual developing cancer from an exposure)
CONTAMINANT RANGES AND MAXIMUM DETECTIONS
DOMESTIC WATER WELLS (AS OF MARCH 1998)
|
Chemical Name |
Concentration Range (µg/l) |
Carcinogenic Screening Value (µg/l) |
Non-carcinogenic Screening Value (µg/l) |
Well ID |
Well Type |
Number of Residences Served |
| 1,1-Dichloroethane | ND - 0.25 |
NA |
800 (MTCA B) | BOW37 | Group B | 6 |
| 1,1,1-Trichloroethane | ND - 0.2 (J) | NA | 200 (MCL/LTHA) | BOW52 | Private | 1 |
| 1,2,4-TMB (pseudocumene) | ND - 0.3 | NA | NA | BOW73 | Group B | 2 |
| Acenaphthene | ND - 1.9 | NA | 600 (Child RMEG) | BOW31A | Private | 1 |
| Acetone | ND - 13 | NA | 1,000 (child RMEG) | BOW52 | Private | 1 + school |
| Arsenic | 10.7 - 26.2 | 0.02 (CREG) | 3 (child chronic EMEG) | BOW31A | Private | 1 |
| Bis (2-ethylhexylphthalate) | 2.7 | 3 (CREG) | 200 (child RMEG) | BOW52 | Private | 1 |
| Bromoform | ND - 0.1 (J) | 4 (CREG) | 200 (child RMEG) | BOW04 | Private | 2 |
| 2-Butanone (MEK) | ND - 6.9 | NA | 6,000 (child RMEG) | BOW52 | Private | 1 |
| Carbon disulfide | ND - 0.4 | NA | 1,000 (child RMEG) | BOW15 | Private | 1 |
| Chloroethane | ND - 0.2 | NA | NA | BOW37 | Group B | 6 |
| Chloroform | ND - 2.7 | 6 (CREG) | 100 (child chronic EMEG) | BOW47 | Private | 2 |
| Chloromethane | ND - 0.2 (J) | 3 (LTHA) | 3 (LTHA) | BOW45 | Private | 1 |
| Chromium | ND - 9 (B) | NA | 50 (child RMEG) | BOW64 | Group A | 1 + school |
| Dichlorodifluromethane | 1.1 - 3.95 | NA | 2,000 (RMEG) | BOW37 | Group B | 6 |
| Diethylphthalate | ND - 1.7 | NA | 8,000 (child RMEG) | BOW31A | Private | 1 |
| Lead | 1 (B) - 67 | NA | 15 (EPA Action level) | BOW64 | Group A | 1 + school |
| Manganese | 589 | NA | 50 (RMEG) | BOW12 | Private | 1 |
| Methylmethacrolate | 0.5 | NA | 640 (MTCA B) | BOW01 | Group B | 8 |
| Methylene chloride | 0.3 | 5 (CREG) | 600 (child chronic EMEG) | BOW33 | Private | 1 |
| Naphthalene | ND - 0.4 (J) | NA | 200 (child inter. EMEG) | BOW35 | Private | 1 |
| Toluene | ND - 0.4 | NA | 200 (child inter. EMEG) | BOW73 | Group B | 2 |
| 1,2,4-Trichlorobenzene | ND - 0.1 (J) | NA | 70 (LTHA) | BOW35 | Private | 1 |
| Trichlorofluromethane | ND - 0.9 | NA | 3,000 (child RMEG) | BOW56 | Group B | 4 |
| Vinyl chloride | 0.3 - 0.77 | NA | 0.2 (child chronic EMEG) | BOW37 | Group B | 6 |
| Zinc | 398 - 430 | NA | 3,000 (child chronic EMEG) | BOW01 | Group B | 8 |
EMEG: ATSDR's Environmental Media Evaluation Guide. A concentration
in air, soil, or water (or other environmental media), which is derived from
ATSDR's MRL, and below which adverse non-cancer health effects are not expected
to occur. Separate EMEGs can be derived to account for acute, intermediate,
or chronic exposure durations.
RMEG: ATSDR's Reference Dose Media Evaluation Guide. A concentration
in air, soil, or water (or other environmental media), which is derived from
EPA's RfD, and below which adverse non-cancer health effects are not expected
to occur. RMEGs account only for chronic exposure.
MRL: ATSDR's Minimal Risk Level. An estimate of daily human
exposure to a dose of chemical that is likely to be without an appreciable risk
of adverse noncancerous health effects over a specified duration of exposure.
MRLs are derived when reliable and sufficient data exist to identify the target
organ(s) of effect or the most sensitive health effect(s) for a specific duration
via a given route of exposure. MRLs can be derived for acute, intermediate,
and chronic duration exposures by the inhalation and oral routes.
CREG: ATSDR's Cancer Risk Evaluation Guide. A concentration
in air, water, or soil (or other environmental media), which is derived from
EPA's cancer slope factor and carcinogenic risk of 10E-6 for oral exposure.
It is the concentration that would be expected to cause no more than one excess
cancer in a million persons exposed over a lifetime.
CHRONIC RfD: An estimate (with uncertainty spanning perhaps
an order of magnitude) of the daily exposure level of the human population,
including sensitive subpopulations, to a potential hazard that is likely to
be without an appreciable risk of deleterious effects (non-cancer) during a
lifetime. It was developed to be protective for long-term exposure to a compound
(7 years or longer).
CANCER SLOPE FACTOR: A plausible upperbound estimate of the
probability of a response per unit intake of a chemical over a lifetime. The
slope factor is used to estimate an upperbound probability of an individual
developing cancer as a result of a lifetime of exposure to a particular level
of a potential carcinogen.
LOAEL: Lowest Observed Adverse Effect Level. LOAEL's have
been classified into "less serious" or "serious" effects. In dose-response experiments,
the lowest exposure level at which there are statistically or biologically significant
increases in the frequency or severity of adverse effects between the exposed
population and its appropriate control.
NOAEL: No Observed Adverse Effect Level. The dose of a chemical
at which there were no statistically or biologically significant increases in
frequency or severity of adverse effects seen between the exposed population
and its appropriate control. Effects may be observed at this dose, but were
judged not to be "adverse".
MCL: Federal Maximum Contaminant Level. A drinking water regulation
established by the Safe Drinking Water Act. It is the maximum permissible concentration
of a contaminant in water that is delivered to the free-flowing outlet of the
ultimate user of a public water system. MCLs are enforceable standards.
CARCINOGEN: Any substance that can cause or contribute to
the production of cancer.
CONTAMINANT: Any substance or material that enters a system
(the environment, human body, food, etc.) where it is not normally found.
MONITORING WELLS: Wells developed to collect groundwater samples
for the purpose of physical, chemical, or biological analysis to determine the
amounts, types, and distribution of contaminants.
PLUME: An area of chemicals in a given media, such as groundwater
REMEDIAL INVESTIGATION: A study designed to collect the data
necessary to determine the nature and extent of contamination at a site.
COMPARISON VALUE: A concentration used to select contaminants
of concern at hazardous waste sites that are further evaluated in the health
assessment process. The terms comparison value and screening level are often
used synonymously.
CLHA: Child Long-Term Health Advisory
MTCA: Model Toxics Control Act. Washington States hazardous
waste cleanup law.
MCLG: Maximum Contaminant Level Goal.
