PUBLIC HEALTH ASSESSMENT
CROSS COUNTY SANITATION LANDFILL
(a/k/a KESSMAN SITE)
PATTERSON, PUTNAM COUNTY, NEW YORK
INTERIM PUBLIC HEALTH HAZARD CATEGORIES
|CATEGORY / DEFINITION||DATA SUFFICIENCY||CRITERIA|
|A. Urgent Public Health Hazard |
This category is used for sites where short-termexposures (< 1 yr) to hazardous substances orconditions could result in adverse health effects thatrequire rapid intervention.
|This determination represents a professional judgement based oncritical data which ATSDR has judged sufficient to support adecision. This does not necessarily imply that the available data arecomplete; in some cases additional data may be required to confirm orfurther support the decision made.||Evaluation of available relevant information* indicates that site-specificconditions or likely exposures have had, are having, or are likely to have inthe future, an adverse impact on human health that requires immediate actionor intervention. Such site-specific conditions or exposures may include thepresence of serious physical or safety hazards.|
|B. Public Health Hazard|
This category is used for sites that pose a publichealth hazard due to the existence of long-termexposures (> 1 yr) to hazardous substance orconditions that could result in adverse health effects.
|This determination represents a professional judgement based oncritical data which ATSDR has judged sufficient to support adecision. This does not necessarily imply that the available data arecomplete; in some cases additional data may be required to confirm orfurther support the decision made.||Evaluation of available relevant information* suggests that, under site-specific conditions of exposure, long-term exposures to site-specificcontaminants (including radionuclides) have had, are having, or are likely tohave in the future, an adverse impact on human health that requires one ormore public health interventions. Such site-specific exposures may includethe 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 exposureand/or toxicologic properties at estimated exposurelevels.
|This determination represents a professional judgement that criticaldata are missing and ATSDR has judged the data are insufficient tosupport a decision. This does not necessarily imply all data areincomplete; but that some additional data are required to support adecision.||The health assessor must determine, using professional judgement, the"criticality" of such data and the likelihood that the data can be obtained andwill be obtained in a timely manner. Where some data are available, evenlimited data, the health assessor is encouraged to the extent possible to selectother hazard categories and to support their decision with clear narrative thatexplains 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 exposureto contaminated media may be occurring, may haveoccurred in the past, and/or may occur in the future,but the exposure is not expected to cause any adversehealth effects.
|This determination represents a professional judgement based oncritical 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 furthersupport the decision made.||Evaluation of available relevant information* indicates that, under site-specific conditions of exposure, exposures to site-specific contaminants inthe past, present, or future are not likely to result in any adverse impact onhuman health.|
|E: No Public Health Hazard|
This category is used for sites that, because of theabsence of exposure, do NOT pose a public healthhazard.
|Sufficient evidence indicates that no human exposures tocontaminated media have occurred, none are now occurring, andnone are likely to occur in the futur|
This summary was prepared to address comments and questions on the Public Health Assessment for theKessman/Cross County site in Patterson, Putnam County. The public was invited to review the draft duringthe public comment period which ran from July 15 to August 28, 1998. We received oral and writtencomments from residents and written comments from the New York City Department of EnvironmentalProtection (NYC DEP). Similar comments may be consolidated or grouped together and some statementsreworded to clarify the comment. If you have any questions about this summary, you may contact the NewYork State Department of Health's (NYS DOH) Outreach Unit at the toll free number: 1-800-458-1158,extension 27530.
I suggest that further studies be done about a possible link between the dump site and residents on CornwallHill Road with autoimmune diseases. I have been diagnosed with rheumatoid arthritis and others who resideon Cornwall Hill Road also have autoimmune diseases.
Based on the information reviewed there was no evidence that the residents living near the landfill are beingor have been exposed to levels of site related contaminants in soil, leachate, sediment, surface water, groundwater or air that would cause adverse health effects. Based on this information a health study of arearesidents is not warranted at this time. Residents of the area can call the NYS Center for EnvironmentalHealth at 1-800-458-1158 to discuss health concerns they may have related to the site.
The site visit and physical hazards section of the public health assessment, page 6, indicates that people canenter the property by walking around the fence at the driveway. This access seems to indicate that theremedial action is not completely adequate. An additional recommendation should include some action,possible extension of the fencing to deny access of unauthorized persons.
Although there is a fence over 3/4 of the site, there is no fence on the swamp side of the site. Access to thesite from the swamp side, however, is difficult. The fencing is not meant to be a remedial action, but insteadit is meant to limit access to the site, protect the landfill cover and alert individuals to the fact that the area isan inactive hazardous waste site. Possible exposures to site-related contaminants could occur fromtrespassing if the integrity of the landfill cover is compromised or if leachate were to leave the landfill andmigrate to accessible areas. For those reasons, we recommend implementation of the long-term monitoringprogram.
If the polychlorinated biphenyls (PCBs) contaminated sediment which is below the landfill cap caused off-site contamination, how and when will this PCB contamination be removed?
Levels of PCBs as high as 2970 parts per million (ppm) were found in the drum removal area which is east of the landfill in the area between it and the Great Swamp. This PCB contaminated soil was excavated during drum removal and taken off-site to an appropriate facility. The drum area is believed to be the source of the PCB contamination in the Great Swamp. The low levels of PCBs (12.2 ppm) found in the Great Swamp are slightly above the New York State Department of Environmental Conservation (NYS DEC) level of 10 ppm in its Technical and Administrative Guidance Memorandum (TAGM). The low-level PCB-contaminated soil was excavated and placed below the landfill cap. PCBs placed beneath the cap are not expected to migrate.
Based solely on the public health assessment (PHA) and the remedial actions completed to date, we agreewith the general recommendation that the NYS DEC should continue with long-term monitoring. However,the details of the monitoring program should be provided and evaluated to ensure that the monitoringprogram encompasses all of the areas of potential concern: surface and groundwater, landfill leachate,discharges to/from Great Swamp and Muddy Brook and the four private groundwater wells. To date thequarterly monitoring of the surface water, groundwater and landfill leachate as required by the 1994 Recordof Decision (ROD) has not been accomplished. Therefore, no decisions should be made until this requiredquarterly monitoring has been accomplished and the results analyzed. Further, the leachate collection systemwas constructed for possible future use should monitoring results indicate that its use is warranted. To date,it has not been activated. The Great Swamp supports many varieties of fish and is used frequently byfishermen. The activation of the leachate collection system would help minimize further impact to all thebiota as well as the fishermen through the food chain. This site has the potential to cause a long-termcumulative public health hazard to the drinking water quality of the residents of Patterson. Protection fromthese cumulative effects can also be mitigated by the activation of the leachate collection system. I urge youto activate this leachate collection system now to prevent further contamination of the Great Swamp and itsdrinking water resources.
Some, but not all of the long-term monitoring specified in the 1994 Record of Decision (ROD) has beendone. Samples of landfill leachate were collected in September 1996, July and August 1997 and October andDecember 1998. Surface water, groundwater and private well samples were collected in July and August1997 and December 1998. The data collected from 1996 to 1998 in two areas of the site were high incompounds indicative of landfill leachate. The specific data are presented in the PHA. The NYS DOHrecommends that the leachate collection system be activated to reduce contamination entering the GreatSwamp. The NYS DEC will determine the feasibility of activating the leachate collection system.
On page 2 the document states that the railroad tracks separate the east and north sides of the site, which arewetlands, from the Great Swamp of Patterson. Historically the site in question was part of the Great Swamp,DP-22. However, after dumping occurred in the 1970's, the NYSDEC delisted the filled portion of the dumpfrom DP-22 because it was no longer a wetland, but a dump! This is a NYS DEC Class 1 wetland; therefore,the Kessman site requires the highest possible remediation and protection.
Once the landfill filled that portion of the Great Swamp, it technically had to be "reclassified" as a landfill. However, the remainder of the Great Swamp is still a NYS DEC Class 1 wetland and will continue to receivethe appropriate protection from contamination to prevent its degradation.
Recently the Department of United States Geological Surveys (USGS), working with the NYC DEP, documented that the Great Swamp received over 75% of its water from groundwater. On page 5 you statethe groundwater is contaminated with VOCs and SVOCs. Other contaminants are listed on page 12 and 13. All these contaminants are above NYS drinking water standards. The documented groundwater flow isnorth-easterly from the landfill towards the Great Swamp. The Great Swamp is the headwaters of the CrotonReservoir system and overlies the aquifer providing drinking water to the residents of Patterson andsurrounding communities. Protection of this vital resource is of utmost importance.
The PCB drum removal and the placement of a cap on the landfill were done to minimize movement ofcontaminated groundwater from the site into the Great Swamp. There are monitoring wells between the GreatSwamp and the landfill which are part of the system to detect whether site-related contaminants are enteringthe Great Swamp and subsequently the Croton Reservoir. Sampling of these wells is a part of the long-termmonitoring program.
The addition of the cover will not stop the continued contamination of the groundwater; it will only slowdown the flow. The rise and fall of the water table beneath the site will continue to wash contaminants fromthe site into the Great Swamp.
Although there is no liner on the bottom of the landfill, the cap or cover on top of the landfill willsignificantly reduce the flow of water through the landfill. Prior to the installation of the cap, rain andsurface water runoff were able to freely flow through the landfill, moving contaminants from the fill to thegroundwater. This caused the greatest transfer of contaminants from the site to the groundwater. Theinstallation of the cap minimizes this transfer of water through the contaminants, reducing the amount ofcontaminants in groundwater. There will be seasonal shifts of groundwater which are more vertical thanlateral due to rise and fall of the watertable. Vertical fluctuation in groundwater will not result in significantadditional groundwater contamination. Monitoring wells are in place to determine if contaminants areflowing towards the Great Swamp.
The leachate collection system was constructed for possible future use should monitoring results indicate thatits use is warranted. To date, it has not been activated. On Page (14) you state, "remedial activities at thesite, including placing a cover and installing a leachate collection system should minimize the potential forexposures of health concern..." (Emphasis added). I urge you to activate this leachate collection system nowto prevent further contamination of the Great Swamp and its drinking water resources. The Great Swampsupports many varieties of fish and is heavily used by fishermen. The activation of the leachate collectionsystem would help minimize further impact to all the biota as well as the fishermen through the food chain. This site has the potential to become a long-term public health hazard to the residents of Patterson who useprivate wells. Protection from these potential effects can be mitigated by the activation of the leachatecollection system.
Although the leachate collection system is in place, the intention was to activate the system only if significantsite-related leachate is discharged from the landfill. As stated previously, some, but not all of the long-termmonitoring specified in the 1994 Record of Decision has been done. The surface water sampling datacollected near the landfill were high in compounds indicative of landfill leachate, suggesting potentialleachate outbreak. These specific data are included in the PHA. The NYS DOH recommends that theleachate collection system be activated to reduce contamination entering the Great Swamp. The NYS DECwill determine the feasibility of activating the leachate collection system.
The PHA indicated that the NYS DEC removed a total of 272 drums and contaminated soil from the landfill,but provided no information as to whether the drums were intact or corroded, and provides no information onthe contents and concentration of potential contaminants in the drum or excavated soils. This information(which most likely is in one of the referenced documents) should be included in the PHA, as it provides someindication for the potential for D or L -NAPLs to be present. In turn, this information is needed to evaluatethe likely effectiveness of the cleanup, as well as the adequacy of the groundwater investigation.
Although some of the 272 drums removed from the landfill were in fair condition, most were in badcondition. All of the drums were over packed, placed in larger drums to contain their contents. The majorityof drums contained waste materials such as concentrated solvents which were inconsistent with thehousehold waste historically disposed of in the landfill. The excavated drums and soils were taken off-site toa designated disposal facility. After the drum and soil excavation, additional soil samples were collected toconfirm the contamination had been appropriately removed.
The PHA indicates that various constituents were detected in leachate seeps located between the east side ofthe landfill and the railroad tracks. The NYS DOH indicated that this was not an issue for potential futureexposures because of the placement of a landfill cap and the installation of a leachate collection system. While a cap and a leachate collection system is a presumptive remedy for a landfill, there is no evaluation inthe PHA as to whether the leachate collection system is adequate, and there is no evaluation about theadequacy of the Operations and Maintenance for the cap and leachate system. It should be noted that thisinformation is probably available in the ROD for the site. However, we believe that NYS DOH is correct intheir analysis that these actions (cap and leachate collection system) will minimize the potential for exposure,additional details or general engineering designs criterial for the cap should be included in the PHA.
The NYS DOH will summarize and evaluate these data, with respect to the leachate collection system, in aletter to NYS DEC. It will be placed in the site's document repository.
The PHA indicates that surface water and sediment sampling was limited to two events. Only one off-sitesample location was selected downstream of the landfill at the confluence of a culvert and Muddy Brook. The PHA should clarify whether this off-site downstream location was sampled once or twice. The PHAindicates that some constituents were detected in surface water and sediments in the on-site samples collectedeast of the landfill and west of the railroad embankment, but that none were detected in the sample at theconfluence with Muddy Brook. Based on these results, the PHA concluded that potentially significant pastor future exposure to contaminants in surface water or sediments is unlikely. Based on the informationcontained in the PHA, it is impossible to fault this conclusion. However, given the concentrations detected atthe on-site locations, and the number of drums removed, this conclusion seems to be based on very limiteddata. In that context, the nature of the long-term monitoring program should be specified, particularly withregard to any surface water sampling. Moreover, we believe that the groundwater and surface waterinvestigations may not have been adequate for determining potential impacts on the Great Swamp, and byextension, on the surface water leading from the Great Swamp.
As stated in Response #4, some, but not all of the long-term monitoring has been done. Periodic samplingwas conducted at the site. Part of that periodic sampling included groundwater and surface water sampling. During the 1993 and 1994 on-site investigations, surface and groundwater samples were collected at strategicareas on and off-site where the potential for off-site migration into the Great Swamp would be greatest. Multiple surface and groundwater samples were collected to determine the landfill's possible impact on theGreat Swamp. Site-related contaminants were detected in the groundwater samples at levels slightly abovethe NYS DOH drinking water standards on-site and off-site within the Great Swamp. Site-relatedcontaminants were detected in the surface water samples at levels slightly above the NYS DOH drinkingwater standards on-site, but no contaminants were detected in the surface water samples from the GreatSwamp or the Muddy Creek. December 1998 monitoring results, however, show that surface water samplescontained VOCs. Although groundwater data did not show any VOC contamination, heavy metals weredetected at elevated levels during recent sampling.
Additional information on the groundwater investigation should be provided in the PHA, based on theconcentration of constituents detected on-site and in drums. Was or is there a potential for a non-aqueousphase liquid or (NAPL) to be present and was the groundwater investigation adequate to detect a dense, non-aqueous phase liquid or (D-NAPL)? Secondly, the PHA indicates that groundwater flows from the west toeast, from the site to the Great Swamp. However, no downgradient off-site wells were installed in the GreatSwamp, which is a discharge area for groundwater. Moreover, no surface water or sediment samples werecollected from within the Great Swamp, near the railroad embankment, to determine the potential forchemical constituents to migrate via groundwater, under the railroad embankment to determine the potentialfor chemical constituents to migrate via groundwater, under the railroad embankment and into the GreatSwamp. The PHA should evaluate the adequacy of the groundwater investigation for determinating past orfuture exposures via the groundwater to surface water pathway, both for recreational use and for use as a water supply.
Although high levels of volatile organic compounds (VOCs) were detected in the drums neither NAPL nor
D-NAPL were detected in the groundwater on- or off-site. Before the site remediation, drum andcontaminated soil removal, and the placement of the landfill cap, multiple soil and groundwater sampleswere taken in the Great Swamp and the site side of the railroad tracks. No site-related contaminants werefound on the off-site side of the railroad track within the swamp. Monitoring wells were placed between thelandfill and the Great Swamp to detect possible site-related contaminated groundwater flowing from the site towards the Great Swamp.
- 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 chemical 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.