PUBLIC HEALTH ASSESSMENT
MOHAWK TANNERY SITE
NASHUA, HILLSBOROUGH COUNTY, NEW HAMPSHIRE
Cancer incidence is the number of new cases of cancer, by specific type, that is reported for a particular area over a specific period of time. A review of the cancer incidence for selected cancers, as used in this health assessment, can help determine whether a community is experiencing greater than normal levels of cancer.
The American Cancer Society estimates that approximately 8.4 million Americans alive today have a history of cancer. For men, the lifetime risk of developing cancer is 1 in 2; for women, the lifetime risk is 1 in 3. In 2000, about 1,220,100 new cases of cancer are expected to be diagnosed .
Standardized Morbidity Ratio (SMR) Calculation Methodology
To help determine whether a community is experiencing a greater than expected rate of cancer, cancer statistics can be reviewed. First, it is necessary to verify the number of cases of cancer that actually occurred in the community. This is referred to as the observed cases. Observed cases are found through a cancer registry, in this case, the New Hampshire State Cancer Registry. Next, it is necessary to calculate the expected cases, which are the number of cases that would be anticipated to occur. The expected cases are a mathematical prediction of the number of cases that would be expected in a particular community population based on the number of cases that have occurred in a reference population, such as a metropolitan area, a state, or the nation as a whole. Prediction of the expected cases takes into account the age, sex, and race of persons in the community and assumes that the community population is similar enough to the reference population that the same proportion of any given cancer will be reflected in the community population. In the case of those living in Nashua the population of the state of New Hampshire could not be used as the reference population due to the fact that the population of Nashua (1999 Office of State Planning estimates 83,900) makes up approximately 7% of the total state population (1999 Office of State Planning estimates 1,201,000). Therefore, estimated rates for the United States, derived from the Surveillance, Epidemiology and End Results (SEER), a program of the National Cancer Institute were used as the next best reference population . Taking into account the racial make-up for the city of Nashua with 95% being considered white, rates used were of SEER data for the white population of the United States.
EXAMPLE OF SMR CALCULATION:
If the reference population has 1000 persons and 25 cases of cancer, the proportion of cancer in that population would be 25 in 1000 (25/1000) or .025. If the community has a population of 100, the method to calculate the expected number of cancers in the community would be to multiply the population of the community, 100 by .025, the proportion seen in the reference population (100 x .025). The expected number of cancers in the community would be 2.5.
The relationship between the observed and the expected cases is called a Standardized Morbidity Ratio (SMR). If the observed number of cases is the same as the expected number of cases, the SMR is 1.0 and the community has neither a measurable increased nor decreased cancer incidence. If the observed number of cancer cases is lower than the expected number, then the SMR is less than 1.0 and the community has fewer cases than expected. If the observed number of cancer cases is higher than the expected number of cases, the SMR is greater than 1.0 and it is possible that the community is experiencing a greater than expected rate of cancer.
|Standardized Morbidity Ratio||What It Means|
|= 1.00||The number of cases in the community is neither higher nor lower than what would be expected based on the number of cases in the reference population.|
|< 1.00||The number of cases is lower than would be expected based on the reference population. It is possible that the community is experiencing less cancer than would be expected.|
|> 1.00||The number of cases is greater than would be expected based on the reference population. It is possible that the community is experiencing more cancer than would be expected.|
A SMR of 1.5 indicates a 50% increase in cases over what was expected, and .90 indicates a 10% decrease in cases. Interpretation of the SMR depends not only on its size, but also on its stability. A SMR based on a few cases is considered to be unstable, or more prone to chance, than would be the same SMR calculated from a large number of cases.
|For example, a SMR of 2, which indicates a 100% increase in observed cancers over expected cancers, would occur if you expected 1 case and observed 2 cases; it would also occur if you expected 100 cases and observed 200 cases. However, in the first instance the SMR is based on 1 excess case, whereas, in the second instance, the SMR is based on 100 excess cases. Both represent a 100% increase, but the latter is far more stable.|
Before the conclusion that a community is experiencing an increase or decrease in cancer can be accepted, it is necessary to determine whether the increase is statistically significant. Statistical significance takes into account, by means of a statistical test, variations in the populations and the numbers that are being compared. The SMR assumed that the populations were the same, whereas statistical significance examines the variability in the data.
When an observation is determined to be statistically significant, the association is acknowledged to be due to more than chance alone. Although this does not determine causation, it does indicate that an apparent increase in the rate is probably not due to chance alone. Scientists generally assume statistical significance when there is less than a 5% chance (probability) that a particular outcome occurred by chance alone.
|One way of looking at chance is in terms of flipping a coin. Since one has a 50/50 chance of getting either heads or tails in one flip of a coin, one would expect in 10 flips of a coin to get 5 heads and 5 tails. However, it is possible to get 7 heads and 3 tails, 4 heads and 6 tails, or even 10 heads and no tails, purely by chance. The test for statistical signficance helps to sort out how often one would expect two things to occur together due to chance alone. Data are said to be statistically significant when the occurrence by chance alone is found to be small.|
Since the data used to determine the SMR is a product of estimates, the SMR is an average or an estimate. The "true" ratio is the exact ratio that would be found if we knew exactly how many cases to expect in the population (because a larger reference population is used to estimate the expected occurrence of cancer in a smaller population) and exactly how many cases occurred (since every case of cancer may not have been recorded.
Since it is not possible to determine the true ratio, a range is defined around the SMR and is used to estimate the true ratio. Within this range, it is possible that any number could be the true ratio. Statistical significance is determined by looking at the range around the SMR. This range is referred to as a confidence interval (CI). A 95% confidence interval (95% CI) is a range of numbers around the SMR in which the true ratio falls 95% of the time.
To determine statistical significance, a 95% confidence interval is developed for the SMR. A 95% CI which includes 1, such as (0.96 - 1.13) is not statistically significant because, it is possible that the true ratio could be any number in that range, including 1. A 95% CI which does NOT include 1, such as (1.10 - 1.25), is considered to be statistically significant because it is unlikely that the true ratio would be less than or equal to 1 strictly because of chance. As with the SMR, the stability of the confidence interval must also be evaluated. A narrow confidence interval, (1.5 - 1.7), indicates that the calculated SMR is fairly close to the true SMR for the population and is considered to be stable. A wide confidence interval, (1.1 - 5.7), indicates that the true SMR could be much higher or lower than the calculated SMR and is considered to be unstable. In this situation, even though the SMR is determined significant, the confidence interval indicates a large variability in the data. Therefore, results should be interpreted with caution.
|For example: if 45 cases of breast cancer are observed and 50 cases of breast cancer are expected, the SMR would be 45/50, or 0.90 (a number less than 1, which means there is not an increase in cancer incidence). However, if 50 cases of breast cancer are expected, and 60 cases of breast cancer are observed the SMR would be 60/50, or 1.20 -a number greater than 1, which means the community might be experiencing a greater rate of cancer than is expected. To determine whether the increase is statistically significant, look at the confidence interval around the SMR. If the 95% confidence interval is (.89 - 1.32), the increase is not statistically significant because it is possible that the true ratio could be any number in that range, including .96 to 1. If, on the other hand, the 95% confidence interval is (1.20 - 1.32), the increase is statistically significant because the confidence interval does not include 1, making it unlikely that the true ratio would be less than or equal to 1 strictly because of chance.|
Relative Risk or (Risk Ratio) Methodology
Most often measures of association in epidemiological analysis utilize the calculation of a relative risk. A relative risk is the risk of an association between an exposure and a disease representing the likelihood of developing the disease in an exposed group of individuals. This and other types of proportion calculations are used to characterize a population by a selected outcome based on an exposure status. The relative risk can further be defined as the ratio of the incidence of disease in an exposed group, divided by the corresponding incidence of disease in a non-exposed group. Residential proximity to the Mohawk Tannery site was the proxy for exposure in that there are distinct land boundries (i.e. a railroad and the Nashua River) that separate the community in the identified census tracts from other communities.
|RR =||Incidence of exposed|
|Incidence of non-exposed|
|A =||People in exposed population with disease.|
|B =||People in the exposed population without disease.|
|C =||People in non-exposed population with disease|
|D =||People in non-exposed population without disease.|
|*Source: Epidemiology in Medicine |
To interpret the results of a risk ratio calculation, the following scale can be used as a guide.
Risk Ratio < 1 no association
Risk Ratio between 1 - 2 weak association
Risk Ratio between 3 - 5 moderate association
Risk Ratio between 6 - 8 strong association
Confidence Interval Calculation for Relative Risk
Calculation of the confidence interval for this statistical test is:
|Confidence Interval = |
Risk Ratio +/- 1.96 (for a 2 sided 95% interval) * sqrt(variance[log RR])
*Source: Epidemiology in Medicine 
There is no difference between the explanation of the confidence interval presented in the SMR calculation section and the one presented here.
Census Tract Determination
Using information obtained from the toxicological assessment as to potential exposure pathways the following census tracts in Nashua, NH were determined to be the most appropriate estimate of the exposed population:
33 011 0104 613
33 011 0104 614
33 011 0104 615
33 011 0104 616
33 011 0104 617
33 011 0104 618
33 011 0104 619
33 011 0104 620
The same cancer cases used in the SMR calculation were then mapped to the identified census tracts using a computerized geographic information system (GIS) (ArcView v3.1). This allowed for an evaluation of the number of cancer cases that fell within the identified census tracts (exposed) as compared to those who were outside of this area (non-exposed). In this case, the non-exposed group was represented by the entire city of Nashua except for those people falling within the identified census tracts. Missing addresses were omitted from the analysis (103 cases or 14% of the total). Among the total omitted data (103) there were 38 records, which were removed due to the inability to map because of the use of a post office box of RFD address.
1 American Cancer Society (2000). Cancer Facts & Figures - 2000. U.S. Department of Health and Human Services. Atlanta, GA. 2000.
2 Ries LAG, et al.. SEER Cancer Statistics Review, 1973-1997. National Cancer Institute. Bethesda, MD 2000.
3 Hennekens Charles H. and Julie Buring. Epidemiology in Medicine. Little Brown and Company 1987. pgs. 77-82 and 254-256.
The New Hampshire Department of Health and Human Services (DHHS) Bureau of Health Risk Assessment (BHRA) is currently conducting a Public Health Assessment of the Mohawk Tannery site in Nashua, New Hampshire, under its' cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). As part of this process, the BHRA staff conducted site visits to the neighborhood surrounding the site on December 13, 2000 and February 21, 2001. This needs assessment was undertaken as part of the planning process to develop a health education program for residents living near the Mohawk Tannery site, and also to direct the focus of the ongoing public health assessment. The goal was to document and respond accordingly to: community interest in the site, community knowledge about the site, preferred sources of information regarding the site, and residents' need for further information.
A. SCHEDULED RELEASE OF PHA
The Public Health Assessment is scheduled to be completed in the Summer of 2001.
B. ONGOING ACTIVITIES
In addition to this Needs Assessment for the Public Health Assessment, an Epidemiologist has completed a data analysis of cancers reported for the town of Nashua. The results of this analysis will be included in the Public Health Assessment document. An Environmental Risk Analyst is currently reviewing environmental data taken from the site and surrounding area.
A brief survey (Attachment A) was developed and distributed to residents living in the adjacent neighborhood. Due to the fact that only a small number of the residents' addresses were known, the DHHS Health Educator conducted a site visit to obtain street names and house numbers to compile a more complete mailing list for the mailing of the needs assessment survey. On February 8, 2001, DHHS mailed 199 surveys to the citizens who lived in close proximity to the site. Included in the survey packet was a fact sheet describing who would be conducting the public health assessment, what is the purpose of doing a health assessment, what they could expect to learn from the public health assessment, as well as an explanation of the process of conducting a health assessment. Residents were also made aware that DHHS staff would be conducting a Public Availability Session on February 21, 2001.
All completed surveys were returned to DHHS by mail. The survey results were compiled and have been incorporated into this Educational Needs Assessment. A detailed summary of responses is attached as Attachment B.
Along with the Educational Needs Assessment survey, residents had the opportunity to express concerns and questions at a Public Availability Session that was held on February 21, 2001.
Another source of community concerns was an earlier public meeting that the U.S. EPA had conducted on May 18, 2000. A DHHS' representative was present at the meeting and recorded community concerns for incorporation into the public health assessment.
D. KEY FINDINGS
- A larger percentage of residents are interested in the Mohawk Tannery site than was previously thought.
- Currently, most residents receive site information through newspapers, mail, and the local cable station.
- Most residents would prefer to receive site information through the mail and the local newspaper.
- Nearly all of the survey respondents expressed a desire for information on contaminants found on-site, health effects and the routes of exposure.
- Half of the respondents indicated that they smell odors coming from the site.
- Almost half of the respondents indicated that they walk on an adjacent property, while one quarter indicated that they walk on the Mohawk Tannery property itself.
- Slightly over ¾ of respondents are "very interested" in the site.
- Almost two-thirds of the respondents have lived in their homes over 10 years.
- Few families have young children under the age of six.
- Over one quarter of respondents indicated that they would like their family physician to receive information about the site and the health effects of the chemicals that exist there.
- Respondents were mainly concerned with:
- The health effects of exposure to site contaminants for themselves, their families, and their pets;
- Extent of the contamination.
- Whether or not they have been exposed to site contaminants.
- The association between "odors" and "exposure to chemicals".
- Current activities regarding site clean up.
A Public Health Assessment (PHA) focuses on identifying and evaluating any public health impacts from contaminants released from a hazardous waste site and provides information to the community about health risks and effects posed by contact with site contaminants. A PHA typically consists of two, and under certain circumstances, three, main components:
- A review of available environmental data;
- A compilation and response to community concerns;
- A review of health outcome data, when applicable.
This Educational Needs Assessment is a tool that will help focus the second component of the PHA. Health Risk Assessors use the information gathered during a needs assessment to address a community's concerns, and to answer questions in the PHA document.
There was a higher than expected return rate (33.2%) on this mail-in survey, showing that residents were very interested in finding out more about the site and any potential health effects to them.
Almost two-thirds (62.1%) of survey respondents have lived in their homes over 10 years. Although very few homes (13.6%) have children under the age of six currently living there, length of residency responses indicate a high likelihood that many children have grown up in the homes surrounding the Mohawk Tannery site.
Residents' Attitudes About the Mohawk Tannery
Respondents were asked two questions to gauge their attitudes regarding the site; whether or not they smelled odors coming from the site, and how interested they were in the site. Thirty-three (50.0%) of the respondents indicated that they smelled odors coming from the site. Most descriptions of the odor described it as "sulfuric" in nature, and "nauseating at times". Many of the respondents indicated that this odor was much stronger and occurred with more frequency while the tannery was in operation.
When asked their level interest in the site, 78.8% of respondents indicated that they were "very interested", while 19.7% indicated that they were "somewhat interested". One respondent indicated that they were "not interested" in the site.
Residents' Knowledge of the site
Although no specific questions were asked about residents' knowledge of the site and its' contaminants, it is interesting to note that not once, in the survey or during the public availability session, did a respondent ask about a specific chemical or class of chemicals. Almost all respondents (92.4%) did request more information about the chemicals on the site, while even more (97.0%) requested information about the health effects of the chemicals that are associated with the site.
Residents were also very interested in having their family physicians made aware of the health effects of the chemicals found at the site. Over one-quarter of the respondents (28.8%) supplied their physicians name and address so that they could receive this information.
Associated Health Risks
Survey recipients were asked about their activities that might bring them on or near the site contaminants. Almost one quarter (24.2%) indicated that they walk on the Mohawk Tannery site property. Although most respondents indicated that they do not swim in the Nashua River near the site, 9.1% responded that they do in fact swim or wade in the Nashua River. None of the respondents indicated that they eat fish caught from the river, although some responded that they engage in sport fishing. Almost half of the respondents (44.0%) indicated that they walk in the undeveloped area south (downstream) of the site.
At the end of the survey, respondents were given an opportunity to ask health-related questions or to add any additional comments that they had regarding the Mohawk Tannery site. These comments were recorded and are on file at the Bureau of Health Risk Assessment. However, due to confidentiality issues, the questions were paraphrased to protect the respondents' indentity and to insure that the questions could be included and addressed in the Public Health Assessment.
Sources of Information
Sixty-four of the sixty-six respondents (97.0%) prefer to receive site-related information by mail or as a second preference, the local newspaper, The Nashua Telegraph. Twenty-seven respondents (41.0%) indicated that they would attend a community meeting. All of the respondents completed the name and address section of the survey so that they could be added to the mailing list.
Summary of Community Concerns
The following is a list of questions that was compiled using the written survey and public availability session.
- Can exposure to the chemicals on the site cause cancer, specifically pancreatic cancer?
- Could exposure to the chemicals in the past have caused increased cancer in the residents who live around the site?
- How many people have died of cancer and what type?
- Can exposure to the chemicals on the site cause or worsen respiratory illness, specifically asthma and sinus problems?
- Can the odors from the tannery contribute to health problems?
- Can airborne particles affect neighbors?
CHILDREN AND FAMILIES:
- How could children and fetuses be affected by contaminants from the site?
- Could children who lived in the area while the tannery was in operation experience problems later in life?
- Who would be most at risk from chemical exposure?
- In my family at risk for long-term health problems?
- How is the health of former employees of the tannery affected?
GENERAL HEALTH QUESTIONS:
- Are there health risks associated with the gate being open?
- Are there short-term health effects due to exposure from contaminants at the site?
- What precautions should we be taking?
- How safe is the air for walking outside, sleeping at night?
- Can exposure to site contaminants cause skin rashes, headaches, loss of hair?
Nature of Contamination
- Are the ground water and drinking water affected?
- The neighbors said that the tannery used to haul the hides down the street in trucks. Water would drip out of the trucks onto the road. This water would be washed onto people's lawns. Is this a problem? Would this contaminate the neighbor's yards?
Extent of Contamination
- What kind of radius are the chemicals found in?
- When actual cleanup begins, will we be subjected to any dangers by walking on the site, downstream, or by boating on the river?
- What health dangers will exist during cleanup?
Concerns about Animals
- Can animals that enter the site bring home contamination and be a danger to us?
- Can private wells be tested for contamination?
- Is the collapsed portion of the main building a physical hazard?
Community Educational Needs Assessment Survey
Site: Mohawk Tannery site, Nashua, NH
The New Hampshire Department of Health and Human Services is providing residents who live near the Mohawk Tannery site with this questionnaire in order to determine what health questions the community may have. We will be answering these health questions in a Public Health Assessment of the Mohawk Tannery site that will be available for public comment in the summer of 2001. Please limit your questions about the site to human health topics. For example, we are not able to address issues such as property values or effects on pets.
Thank you for taking the time to complete this survey so that we may better serve you in the future.
How long have you lived at this address? ________________________
Do you have young children (6 years old or younger) who live with you? __ Yes __ No
|__||Newspapers (which one? ___________________________)|
|__||Cable / TV|
|__||Newspapers (which one? ___________________________)|
|Walk on the Mohawk Tannery site property||__ Yes||__ No|
|Swim or wade in the Nashua River||__ Yes||__ No|
|Eat fish from the Nashua River||__ Yes||__ No|
|Walk in the undeveloped area south (downstream) of the site||__ Yes||__ No|
|__||Yes||If yes, please describe the odor and when it occurs:|
|__||The chemicals that are at the site?|
|__||How people may come into contact with those chemicals?|
|__||The health effects associated with those chemicals?|
|Physician Name and |
8. Do you have any other health-related questions about the Mohawk Tannery site that you would like us to discuss in the Public Health Assessment?
Thank you again for taking the time to complete this survey. Please feel free to call us at (603) 271-4664 or toll free in NH at (800) 852-3345 extension 4664. You may also write to us at:
Mohawk Tannery site, Nashua, New Hampshire
Detailed Finding of the Community Educational Needs Assessment
|Surveys Distributed|| |
|Surveys Returned|| |
|Return Rate|| |
|Length of Residency||Responses||Rate|
|Less than 5 years|| |
|5-10 years|| |
|11-20 years|| |
|21-30 years|| |
|31-40 years|| |
|41-50 years|| |
|50+ years|| |
|No response|| |
|Families with Children Age 6 and Under||9||13.6%|
Responses to Survey Questions 1-6
|Cable / TV|| |
|Community Meeting|| |
Newspapers: Nashua Telegraph 66.7%; 1590 Broadcaster 4.5%; Union Leader 4.5%; Boston Globe 1.5%
|(1. Nashua Telegraph 41.0%)|
|(2. 1590 Broadcaster 4.5%)|
|(3. Union Leader 1.5%)|
|(4. Boston Globe 3.0%)|
|Community Meeting|| |
|Walk on the Mohawk Tannery site property|| |
|Swim or wade in the Nashua River|| |
|Eat Fish from the Nashua River|| |
|Walk in the undeveloped area south (downstream) of the site*|| |
* One respondent also noted that they ride bicycles and ATV's on the site.
|No Response|| |
* Seven of these respondents noted that odors were present in the past during the operation of the tannery.
|Very Interested|| |
|Somewhat Interested|| |
|Not Interested|| |
|Chemicals that are at the site|| |
|How people come in contact with those chemicals|| |
|The health effects associated with those chemicals|| |
- 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.
- Additive Effect:
- A response to a chemical mixture, or combination of substances, that might be expected if the known effects of individual chemicals, seen at specific doses, were added together.
- Adverse Health Effect:
- A change in body function or the structures of cells that can lead to disease or health problems.
- Antagonistic Effect:
- A response to a mixture of chemicals or combination of substances that is less than might be expected if the known effects of individual chemicals, seen at specific doses, were added together.
- 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 environment.
- Used in public health, things that humans would eat - including animals, fish and plants.
- See Community Assistance Panel.
- A group of diseases which occur when cells in the body become abnormal and grow, or multiply, out of control
- Any substance shown to cause tumors or cancer in experimental studies.
- See Comprehensive Environmental Response, Compensation, and Liability Act.
- 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.
- Community Assistance Panel (CAP):
- A group of people from the community and health and environmental agencies who work together on issues and problems at hazardous waste sites.
- Comparison Value (CVs):
- Concentrations or the amount of substances in air, water, food, and soil that are unlikely, upon exposure, to cause adverse health effects. Comparison values are used by health assessors to select which substances and environmental media (air, water, food and soil) need additional evaluation while health concerns or effects are investigated.
- 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.
- A belief or worry that chemicals in the environment might cause harm to people.
- How much or the amount of a substance present in a certain amount of soil, water, air, or food.
- 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).
- The amount of a substance to which a person may be exposed, usually on a daily basis. Dose is often explained as "amount 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.
- 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 chemicals 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.
- The study of the different factors that determine how often, in how many people, and in which people will disease occur.
- 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.
- 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.
- Swallowing something, as in eating or drinking. It is a way a chemical can enter your body (See Route of Exposure).
- Breathing. It is a way a chemical can enter your body (See Route of Exposure).
- 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.
- See Cancer.
- Minimal Risk Level. An estimate of daily human exposure - 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.
- 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.
- 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.
- 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.
- A line or column of air or water containing chemicals moving from the source to areas further away. A plume can be a column or clouds of smoke from a chimney or contaminated underground water sources or contaminated surface water (such as lakes, ponds and streams).
- 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.
- A group of people living in a certain area; or the number of people in a certain area.
- Potentially Responsible Party. A company, government or person that is responsible for causing the pollution at a hazardous waste site. PRP's are expected to help pay for the clean up of a site.
- 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 "safety 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.
- The Superfund Amendments and Reauthorization Act in 1986 amended CERCLA and expanded the health-related responsibilities of ATSDR. CERCLA and SARA direct ATSDR to look into the health effects from chemical exposures at hazardous waste sites.
- Sample Size:
- The number of people that are needed for a health study.
- A small number of people chosen from a larger population (See Population).
- 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.
- A branch of the math process of collecting, looking at, and summarizing data or information.
- Superfund Site:
- See NPL.
- A way to collect information or data from a group of people (population). Surveys can be done by phone, mail, or in person. ATSDR cannot do surveys of more than nine people without approval from the U.S. Department of Health and Human Services.
- Synergistic effect:
- A health effect from an exposure to more than one chemical, where one of the chemicals worsens the effect of another chemical. The combined effect of the chemicals acting together are greater than the effects of the chemicals acting by themselves.
- 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.
- The study of the harmful effects of chemicals on humans or animals.
- Abnormal growth of tissue or cells that have formed a lump or mass.
- 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.
A. Urgent Public Health Hazard
This category is used for sites where short-term exposures (< 1 yr) to hazardous substances or conditions could result in adverse health effects that require rapid intervention.
|This determination represents a professional judgement based on critical data which ATSDR has judged sufficient to support a decision. This does not necessarily imply that the available data are complete; in some cases additional data may be required to confirm or further support the decision made.||Evaluation of available relevant information* indicates that site-specific conditions or likely exposures have had, are having, or are likely to have in the future, an adverse impact on human health that requires immediate action or intervention. Such site-specific conditions or exposures may include the presence of serious physical or safety hazards.|
B. Public Health Hazard
This category is used for sites that pose a public health hazard due to the existence of long-term exposures (> 1 yr) to hazardous substances or conditions that could result in adverse health effects.
|This determination represents a professional judgement based on critical data which ATSDR has judged sufficient to support a decision. This does not necessarily imply that the available data are complete; in some cases additional data may be required to confirm or further support the decision made.||Evaluation of available relevant information* suggests that, under site-specific conditions of exposure, long-term exposures to site-specific contaminants (including radionuclides) have had, are having, or are likely to have in the future, an adverse impact on human health that requires one or more public health interventions. Such site-specific exposures may include the presence of serious physical or safety hazards.|
C. Indeterminate Public Health Hazard
This category is used for sites in which critical data are insufficient with regard to extent of exposure and/or toxicologic properties at estimated exposure levels.
|This determination represents a professional judgement that critical data are missing and ATSDR has judged the data are insufficient to support a decision. This does not necessarily imply all data are incomplete; but that some additional data are required to support a decision.||The health assessor must determine, using professional judgement, the Acriticality@ of such data and the likelihood that the data can be obtained and will be obtained in a timely manner. Where some data are available, even limited data, the health assessor is encouraged to the extent possible to select other hazard categories and to support their decision with clear narrative that explains the limits of the data and the rationale for the decision.|
D. No Apparent Public Health Hazard
This category is used for sites where human exposure to contaminated media may be occurring, may have occurred in the past, and/or may occur in the future, but the exposure is not expected to cause any adverse health effects.
|This determination represents a professional judgement based on critical data which ATSDR considers sufficient to support a decision. This does not necessarily imply that the available data are complete; in some cases additional data may be required to confirm or further support the decision made.||Evaluation of available relevant information* indicates that, under site-specific conditions of exposure, exposures to site-specific contaminants in the past, present, or future are not likely to result in any adverse impact on human health.|
E. No Public Health Hazard
This category is used for sites that, because of the absence of exposure, do NOT pose a public health hazard.
|Sufficient evidence indicates that no human exposures to contaminated media have occurred, none are now occurring, and none are likely to occur in the future.|
*Such as environmental and demographic data; health outcome data; exposure data; community health concerns information; toxicologic, medical, and epidemiologic data; monitoring and management plans.
Health assessors use health comparison values to help decide whether compounds may need further evaluation. Health comparison values are derived using information on the toxicity of the chemical and assuming frequent opportunities for exposure to the contaminated media (e.g., a residential setting). For non-cancer toxicity, DHHS typically uses Minimal Risk Levels from the Agency for Toxic Substances and Disease Registry (ATSDR) or Reference Doses from the Environmental Protection Agency (EPA), which are estimates of daily human exposure to a contaminant that is unlikely to cause adverse non-cancer health effects over a lifetime. Cancer risk comparison values are based on EPA's chemical-specific cancer slope factors and an estimated excess lifetime cancer risk of one in one million. Therefore, if the concentration of a chemical is less than its comparison value, it is unlikely that exposure would result in adverse health effects, and further evaluation of exposures to that chemical is not warranted. If the concentration of a chemical exceeds a comparison value, adverse health effects from exposure are not necessarily expected, but potential exposures to that chemical at the site should be evaluated.
Specific types of health comparisons are described below in order of preference for ATSDR Public Health Assessments of Health Consultations.
Health Comparison Values Derived by ATSDR
- Environmental Media Evaluation Guide (EMEG)
- Reference Dose Media Evaluation Guide (RMEG)
- Cancer Risk Evaluation Guide (CREG)
EMEG and RMEG values are used to evaluate the potential for non-cancer health effects. CREG values provude information on the potential for carcinogenic effects. EMEG values are derived for different durations of exposure. Actue EMEGs correspond to exposures lasting less than 14 days. Intermediate EMEGs correspond to exposures lasting between 14 days and 1 year. Chronic EMEGs correspond to exposures lasting longer than 1 year. CREG and RMEG values are derived assuming a lifetime duration of exposure. All of these comparison values are derived assuming opportunities for exposure in a residential setting.
Health Comparison Values Derived by EPA
- Risk-Based Concentrations (RBC) for air, water, soil, and food
- Lifetime Health Advisory (LTHA) for drinking water
The Superfund Technical Support Section in EPA Region III derives Risk-Based Concentrations values using available toxicological information and assuming frequent residential exposures to the contaminated media. A Lifetime Health Advisory is the concentration of a chemical in drinking water that is not expected to cause any adverse non-carcinogenic effects over a lifetime of exposure.
Environmental Regulatory Standards
- Maximum Contaminant Level (MCL) for drinking water
- Maximum Contaminant Level Goal (MCLG) for drinking water
- Ambient Groundwater Quality Standards (AGQS)
- Method 1 Soil Standards (S-1)
A Maximum Contaminant Level Goal is a non-enforceable health goal from EPA which is set at a level at which no known or anticipated adverse effect on the health of persons occur and which allows an adequate margin of safety. A Maximum Contaminant Level is the highest level of a contaminant that is allowed in drinking water, and is an enforceable standard. MCLs are set as close to the MCLG as feasible using the best available treatment technology and taking cost into consideration. Ambient Groundwater Quality Standards and Soil S-1 Standards are regulatory standards for groundwater and soil, respectively, from the New Hampshire Department of Environmental Services (see DES' Administrative Rule Env-Wm 1403 and DES' Risk Characterization and Management Policy, respectively).