COEUR D'ALENE RIVER BASIN
PANHANDLE REGION OF IDAHO
INCLUDING BENEWAH, KOOTENAI, & SHOSHONE COUNTIES
|Location ID||Average Lead Concentration in Residential Yard (mg/kg)||Lead Concentration in Play Area (mg/kg)||Lead Concentration in Garden (mg/kg)||Lead Conc. in Mat||Lead Conc. in Vacuum Bag||Lead Conc. in Exterior Paint||Lead Conc. in Interior Paint||Water Sample Results exceeding RAL/MCL|
|Surface Soil||Sub-surface||Surface Soil||Sub-surface||Surface Soil||Sub-surface||mg/kg)||(mg/kg)||(mg/kg)||(mg/kg)||(µg/L) all first-run|
Method I: Calculation of an estimated dose and comparison to the IOC
The following routes of exposure were considered:Ingestion:
Soil & Dust - Soil and dust ingestion were analyzed quantitatively through calculation of an external dose using average lead concentrations.
Homegrown Foods - Lead levels in garden vegetables were analyzed and their contribution examined quantitatively. However, this data was not incorporated with garden soil lead levels, because sources of the vegetables were not matched with soil sample locations. Future work should include this pathway.
Tap Water - Potable water was included where sampling indicated lead levels exceeded the EPA's action level for lead.
Air particulates - No sampling data were available, therefore background levels were used.
Soil - This pathway is considered negligible as appreciable levels of lead do not penetrate through the skin (ATSDR, 1999)
External dose for children's soil ingestion was calculated:
|Dosesoil =||C x IR x BF x CF |
|=|| Conc x 0.5 x 200mg/day x 10 -6 |
C = concentration of lead in soil, mg/kg
IR = ingestion rate, mg/day
BF = bioavailability factor
BW = body weight, kg
CF = conversion factor (kg to mg)
Concentrations used were the surface soil composite samples. The ingestion rate of 200 mg/day was used as a conservative mean estimate of children's soil ingestion (EPA, 1999)*. An average recommended body weight of 16 kg was used as a mean estimate (EPA, 1999)*. An absolute bioavailability factor of 50% for soil-born lead was used.** This leads to a mean estimate of children's exposed dose, although it needs to be remembered that use of composite surface soil measurements may result in an underestimation of the true concentration, because Ahotspots@ may not be detected.
External dose for children indoor dust ingestion was calculated:
|Dosedust =||C x IR x BF x CF |
|=|| Conc x IR x BF x 10 -6 |
The ingestion rate for dust was taken from estimates of soil and total soil and dust ingestion from the Exposure Factors Handbook (EPA, 1999). Average dust ingestion as a percentage of total soil and dust ingestion was calculated for mean and high-end estimates. Dust ingestion was separated from soil ingestion in this consultation in order to ascertain the specific contributions of dust lead and soil lead to total exposure. Prior studies have ascertained a high indoor dust contribution to total lead exposures (IDHW, 1999).
Similar methodologies were utilized for the other input routes, with the input variables presented in Table B-1 below.
|Route||Lead concentration||Reference|| Ingestion/ |
|Tap water||residence-specific||see data, Appendix A||0.58 L/day||EPA, 1999 |
for children ages 1-4
| Air |
|0.10 µg/m3||EPA, 1994||5 m3/day||EPA, 1994 |
median ventilation rate
|Food||6 µg/day||EPA, 1994, median value||n/a|
L/day = liters per day m3/day = cubic meters per day
µg/m3 = micrograms per cubic meter n/a = not applicable
Method 2: Calculation of expected blood lead levels
Surface soil and indoor house dust lead levels were entered into the EPA's IEUBK model (EPA, 1994). Based on the above calculations, soil and dust incidental ingestion were found to have an appreciably greater contribution to total dose than other exposure routes. Therefore, when using the model, other input distributions were left at default values. Only the effect of soil and indoor dust lead levels were examined. In order to keep the IEUBK model consistent with the previous calculations, soil ingestion as a percentage of total soil and dust ingestion was increased from the default value of 45% to 71%. Expected blood lead levels were then recorded as being between an upper and lower range. Expected blood lead level data can be seen in Appendix C. The blood lead upper and lower range values were then averaged to calculate an average blood lead level, and locations were categorized as having an average blood lead level either greater or less than 10 µg/dl. Several residences had average blood lead levels less than 10 µg/dl, but as the blood lead range included 10 µg/dl they were considered to represent an intermediate category.
In the IEUBK model, the Geometric mean blood lead level which corresponds to a probability of 10 µg/dl is approximately 5 µg/dl. This relationship is sensitive to the geometric standard deviation (GSD): default = 1.6.
Method 3: ATSDR's integrated exposure regression analysis
Numerous longitudinal and cross-sectional studies have attempted to correlate environmental lead levels with blood lead levels. These studies have provided a number of regression analyses and corresponding slope factors () for various media including air, soil, dust, water, and food. The ATSDR integrated exposure regression analysis utilizes slope values from select studies to integrate all exposures from various pathways, thus providing a cumulative exposure estimate expressed as total blood lead (ATSDR 1999).
The general form of the model is:
Pbs = soil lead concentration
Pbd = dust lead concentration
Pbw = water lead concentration
Pbao = outside air lead concentration
Pbai = inside air lead concentration
Pbf = food lead concentration
T = relative time spent
|Air||Children (1-18 yrs)||1.92 + 0.60||Angle et al, 1984 as cited in ATSDR 1999, App D|
|Water||Children|| 0.16 at <15 µg/L |
0.03 at >15 µg/L
|Laxen et al, 1987 as cited in ATSDR 1999, App D|
|Diet||Infants & Toddlers||0.24||Ryu et al, 1983 as cited in ATSDR 1999, App D|
|Soil||Children (1-72 mo)||0.002 + 0.00082||Stark et al, 1982 as cited in EPA 1986|
|Dust||Children (2 yrs old)||0.002 + 0.00066||Stark et al, 1982 as cited in ATSDR 1999, App D|
µg/L = micrograms per liter
|Outdoor Air||0.1-0.2 µg/m3|
|Indoor Air||0.03-0.06 µg/m3 (0.3 x outdoor conc.)|
|Indoor Dust||947 (ave. Indoor dust conc. for 71 residences sampled)|
µg/m3 = micrograms per cubic meter
µg/day = micrograms per day
µg/L = micrograms per liter
Bioavailability was not estimated for this method, as each slope factor is based upon observed blood lead levels correlated with environmental concentrations. The average surface soil concentration was used unless a surface soil concentration was available in a Aplay area@, which was then used. For indoor dust, vacuum bag concentrations were used. For those few residences without vacuum bag data, the average vacuum bag concentration of the other 71 residences with data was used.
The example described within Appendix D of the ATSDR Toxicological Profile for Lead selected larger soil/dust slope values plus or minus three standard deviations to determine the high and low range of blood leads. In this health consultation, values more specific to children aged 1- 3 were selected, and only one standard deviation was added or subtracted for determining the low and high range of blood leads. Subtracting three standard deviations from the slope values selected for this health consultation created negative slopes at the low end, therefore, this was not done. The net effect would be to make the method utilized in this health consultation much less conservative than the example outlined in Appendix D of the Toxicological Profile. Based upon the results provided in Table 5, Appendix D of the Toxicological Profile (which showed this method to correlate well with actual blood lead levels), this would result in an underestimation of the number of residences at which the blood lead range could exceed 10 µg/dl. A benefit to be gained by this method, however, is that those residences most likely to be a problem should be highlighted in this health consultation.
|Location ID||Total Pb dose||Times Dose > IOC|| EPA IEUBK |
| ATSDR Regression |
|Species||System||Exposure Duration|| LOAEL |
|Human||hemato||7 wk at7 days/wk||0.01||decrease ALAD activity; increased RBC porphyrin|
|Human||hemato||21days at 7 days/wk||0.02||increased protoporphyrin IX in RBC (F)|
|Rat||hepatic||20-30 d||0.05||decreased RNA, glycogen: pyknosis of Kupffer cells; increased liver weight|
|Rat||hemato||6-12 mo||0.005||impaired heme synthesis|
|Rat||hepatic||6-12 mo||0.005||decreased glycogen, RNA, sulfhydryl groups, alterations in activities of oxidizing enzymes|
|Rat||cardio||159 d||0.3||increased systolic blood pressure|
|Monkey||neuro||200 d; 5 d/wk||0.05||Impaired nonspatial discrimination at 3 yrs of age|
|Rat||neuro||6-12 mo||0.005||disruption of conditioned responses and motor activity|
|Rat||repro||30 d||0.013||increased prostate weight (M)|
|Rat||repro||30 d||0.014||irregular estrus cycles (F)|
|Rat||repro||6-12 mo||0.05||decreased activity of AIDH, SDH, NAD, and DADPH-diaphorase in spermatogenic epithelium and swelling of lollicular epithelial cells in males|
|Rat||repro||23-30 d||0.005||dystrophy of Leydig cells|
|Rat||cardio||<18 mo; 7 d/wk||0.014||increase in systolic blood pressure|
|Monkey||neuro||1 yr; 7 d/wk||0.19||deficit in fixed interval schedule|
ALAD = aminolevulinic acid dehydratase; cardio = cardiovascular; d = days; F = female; hemato = hematological;
LOAEL = lowest-observable-adverse-effect level; M = male; mg/kg/day = milligrams per kilogram per day; mo =
month; neuro = neurological; RBC = red blood cell; repro = reproductive; RNA = ribonucleic acid; wk = week; yr = year
| BLL |
|<10||Reassess or rescreen in 1 year. No additional action necessary unless exposure source changes.|
|10-14|| Provide Family lead education. |
Provide follow-up testing.
Refer for social services, if necessary.
|15-19|| Provide Family lead education. |
Provide follow-up testing.
Refer for social services, if necessary.
If BLLs persist (i.e., 2 venous BLLs in this range at least 3 months apart) or worsen, proceed according to actions for BLLs 20-44.
|20-44|| Provide coordination of care (case management). |
Provide clinical management (described in text).
Provide environmental investigation.
Provide lead-hazard control.
|45-69||Within 48 hours, begin coordination of care (case management), clinical management (described in text), environmental investigation, and lead hazard control.|
|>70||Hospitalize child and begin medical treatment immediately. Begin coordination of care (case management), clinical management (described in text), environmental investigation, and lead hazard control immediately.|
Absorption: How a chemical enters a person's blood after the chemical has been swallowed, has come into contact with the skin, or has been breathed in.
Acute Exposure: Contact with a chemical that happens once or only for a limited period of time. ATSDR defines acute exposures as those that might last up to 14 days.
Adverse Health Effect: A change in body function or the structures of cells that can lead to disease or health problems.
ATSDR: The Agency for Toxic Substances and Disease Registry. ATSDR is a federal health agency in Atlanta, Georgia that deals with hazardous substance and waste site issues. ATSDR gives people information about harmful chemicals in their environment and tells people how to protect themselves from coming into contact with chemicals.
Background Level: An average or expected amount of a chemical in a specific environment. Or, amounts of chemicals that occur naturally in a specific
Biota: Used in public health, things that humans would eat B including animals, fish and plants.
Cancer: A group of diseases which occur when cells in the body become abnormal and grow, or multiply, out of control
Carcinogen: Any substance shown to cause tumors or cancer in experimental studies.
Chronic Exposure: A contact with a substance or chemical that happens over a long period of time. ATSDR considers exposures of more than one year to be chronic.
Completed Exposure Pathway: See Exposure Pathway.
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA): CERCLA was put into place in 1980. It is also known as Superfund. This act concerns releases of hazardous substances into the environment, and the cleanup of these substances and hazardous waste sites. ATSDR was created by this act and is responsible for looking into the health issues related to hazardous waste sites.
Concern: A belief or worry that chemicals in the environment might cause harm to people.
Concentration: How much or the amount of a substance present in a certain amount of soil, water, air, or food.
Contaminant: See Environmental Contaminant.
Delayed Health Effect: A disease or injury that happens as a result of exposures that may have occurred far in the past.
Dermal Contact: A chemical getting onto your skin. (see Route of Exposure).
Dose: The amount of a substance to which a person may be exposed, usually on a daily basis. Dose is often explained as Aamount of substance(s) per body weight per day@.
Dose / Response: The relationship between the amount of exposure (dose) and the change in body function or health that result.
Duration: The amount of time (days, months, years) that a person is exposed to a chemical.
Environmental Contaminant: A substance (chemical) that gets into a system (person, animal, or the environment) in amounts higher than that found in Background Level, or what would be expected.
Environmental Media: Usually refers to the air, water, and soil in which chemcials of interest are found. Sometimes refers to the plants and animals that are eaten by humans. Environmental Media is the second part of an Exposure Pathway.
U.S. Environmental Protection Agency (EPA): The federal agency that develops and enforces environmental laws to protect the environment and the public's health.
Epidemiology: The study of the different factors that determine how often, in how many people, and in which people will disease occur.
Exposure: Coming into contact with a chemical substance.(For the three ways people can come in contact with substances, see Route of Exposure.)
Exposure Assessment: The process of finding the ways people come in contact with chemicals, how often and how long they come in contact with chemicals, and the amounts of chemicals with which they come in contact.
Exposure Pathway: A description of the way that a chemical moves from its source (where it began) to where and how people can come into contact with (or get exposed to) the chemical.
ATSDR defines an exposure pathway as having 5 parts:
- Source of Contamination,
- Environmental Media and Transport Mechanism,
- Point of Exposure,
- Route of Exposure, and
- Receptor Population.
When all 5 parts of an exposure pathway are present, it is called a Completed Exposure Pathway. Each of these 5 terms is defined in this Glossary.
Frequency: How often a person is exposed to a chemical over time; for example, every day, once a week, twice a month.
Hazardous Waste: Substances that have been released or thrown away into the environment and, under certain conditions, could be harmful to people who come into contact with them.
Health Effect: ATSDR deals only with Adverse Health Effects (see definition in this Glossary).
Indeterminate Public Health Hazard: The category is used in Public Health Assessment documents for sites where important information is lacking (missing or has not yet been gathered) about site-related chemical exposures.
Ingestion: Swallowing something, as in eating or drinking. It is a way a chemical can enter your body (See Route of Exposure).
Inhalation: Breathing. It is a way a chemical can enter your body (See Route of Exposure).
LOAEL: Lowest Observed Adverse Effect Level. The lowest dose of a chemical in a study, or group of studies, that has caused harmful health effects in people or animals.
MRL: Minimal Risk Level. An estimate of daily human exposure B by a specified route and length of time -- to a dose of chemical that is likely to be without a measurable risk of adverse, noncancerous effects. An MRL should not be used as a predictor of adverse health effects.
NPL: The National Priorities List. (Which is part of Superfund.) A list kept by the U.S. Environmental Protection Agency (EPA) of the most serious, uncontrolled or abandoned hazardous waste sites in the country. An NPL site needs to be cleaned up or is being looked at to see if people can be exposed to chemicals from the site.
NOAEL: No Observed Adverse Effect Level. The highest dose of a chemical in a study, or group of studies, that did not cause harmful health effects in people or animals.
No Apparent Public Health Hazard: The category is used in ATSDR's Public Health Assessment documents for sites where exposure to site-related chemicals may have occurred in the past or is still occurring but the exposures are not at levels expected to cause adverse health effects.
No Public Health Hazard: The category is used in ATSDR's Public Health Assessment documents for sites where there is evidence of an absence of exposure to site-related chemicals.
PHA: Public Health Assessment. A report or document that looks at chemicals at a hazardous waste site and tells if people could be harmed from coming into contact with those chemicals. The PHA also tells if possible further public health actions are needed.
Point of Exposure: The place where someone can come into contact with a contaminated environmental medium (air, water, food or soil). For examples:
the area of a playground that has contaminated dirt, a contaminated spring used for drinking water, the location where fruits or vegetables are grown in contaminated soil, or the backyard area where someone might breathe contaminated air.
Population: A group of people living in a certain area; or the number of people in a certain area.
Public Health Assessment(s): See PHA.
Public Health Hazard: The category is used in PHAs for sites that have certain physical features or evidence of chronic, site-related chemical exposure that could result in adverse health effects.
Public Health Hazard Criteria: PHA categories given to a site which tell whether people could be harmed by conditions present at the site. Each are defined in the Glossary. The categories are:
- Urgent Public Health Hazard
- Public Health Hazard
- Indeterminate Public Health Hazard
- No Apparent Public Health Hazard
- No Public Health Hazard
Receptor Population: People who live or work in the path of one or more chemicals, and who could come into contact with them (See Exposure Pathway).
Reference Dose (RfD): An estimate, with safety factors (see safety factor) built in, of the daily, life-time exposure of human populations to a possible hazard that is not likely to cause harm to the person.
Route of Exposure: The way a chemical can get into a person's body. There are three exposure routes:
- breathing (also called inhalation),
- eating or drinking (also called ingestion), and
- or getting something on the skin (also called dermal contact).
Safety Factor: Also called Uncertainty Factor. When scientists don't have enough information to decide if an exposure will cause harm to people, they use Asafety factors@ and formulas in place of the information that is not known. These factors and formulas can help determine the amount of a chemical that is not likely to cause harm to people.
Source (of Contamination): The place where a chemical comes from, such as a landfill, pond, creek, incinerator, tank, or drum. Contaminant source is the first part of an Exposure Pathway.
Special Populations: People who may be more sensitive to chemical exposures because of certain factors such as age, a disease they already have, occupation, sex, or certain behaviors (like cigarette smoking). Children, pregnant women, and older people are often considered special populations.
Statistics: A branch of the math process of collecting, looking at, and summarizing data or information.
Subclinical: The presence of a disease without apparent symptoms in the individual. May be an undiagnosed or early stage of a disease, or result in impaired development or reduced potential. Effects may only be apparent after scientific comparisons of many children.
Superfund Site: See NPL.
Toxic: Harmful. Any substance or chemical can be toxic at a certain dose (amount). The dose is what determines the potential harm of a chemical and whether it would cause someone to get sick.
Toxicology: The study of the harmful effects of chemicals on humans or animals.
Uncertainty Factor: See Safety Factor.
Urgent Public Health Hazard: This category is used in ATSDR's Public Health Assessment documents for sites that have certain physical features or evidence of short-term (less than 1 year), site-related chemical exposure that could result in adverse health effects and require quick intervention to stop people from being exposed.
Figure 1 - Effects of Inorganic lead in children and adults
* The typical infant and toddler oral exploratory behaviors include repetitive mouthing which results in continuous ingestion by these children of small amounts of dust and soil over the course of a play period, ultimately adding up to a daily intake of 100 to 200 mg (Mushak 1998).
* 16 kg (roughly 35 pounds) is approximately the body weight of a child one to two years of age. The Centers for Disease Control and Prevention (CDC) has said that focus should be on children between the ages of 12 and 36 months (1-and 2-year-old children) because blood lead levels tend to be highest in this age group, and more chiuldren in this age group have blood lead levels equal to or greater than 10 µg/dl (CDC, 1997).
**The value of 50% bioavailability was selected as representative of the upper range of values seen in a variety of studies measuring absolute and relative lead bioavailability (Mushak, 1998; Maddaloni, 1998; Henningsen, 1998).