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HEALTH CONSULTATION

Health Risks Associated With Exposure to Contaminated Sediments

RUDDIMAN CREEK WATERSHED
(a/k/a RUDDIMAN DRAIN AREA)
MUSKEGON, MUSKEGON COUNTY, MICHIGAN


SUMMARY

The Ruddiman Creek watershed covers approximately 5.6 square miles in Muskegon County, Michigan. The west, north and main branches of Ruddiman Creek flow through areas of dense residential development. The main branch of the creek is located less than 100 feet from several apartment complexes and the Glenside Elementary School (Muskegon Public Schools). The three branches of the creek flow into Ruddiman Pond, which is located adjacent to McGraft Park, a popular suburban park. Area residents, including children, play in and around the creek branches and in the pond.

Based on existing sediment chemistry data, no apparent public health hazard exists for the sediments in Ruddiman Pond, or the north and west branches of Ruddiman Creek. However, sediments in the main branch of Ruddiman Creek, particularly the area between Glenside Avenue and Barclay Road, pose an indeterminate public health hazard. Sediments in this area are contaminated with polychlorinated biphenyls (PCBs) and lead at levels of potential concern for children playing in and around the creek.

The Michigan Department of Community Health (MDCH) recommends additional sampling to further characterize the contamination in sediments in the main branch of the creek. Sampling and analysis of fish in the watershed is also recommended. Until contaminant levels and the extent of contamination can be fully determined, the MDCH recommends posting warning signs in areas of the main branch of the creek where children are likely to be present. The MDCH strongly encourages the Ruddiman Creek Task Force to continue its public education efforts at the Glenside Elementary School. The MDCH will be available to provide assistance if requested.


BACKGROUND AND STATEMENT OF ISSUES

The Michigan Department of Environmental Quality (MDEQ) has asked the Michigan Department of Community Health (MDCH) to evaluate the human health risk associated with potential exposures to contaminated sediments in the Ruddiman Creek Watershed. The watershed is located in Muskegon County, Michigan. The west, north, and main branches of the creek flow through residential areas and into Ruddiman Pond. The pond empties into Muskegon Lake, which is connected to Lake Michigan via the Muskegon channel.

In 1998, following passage of the Clean Michigan Initiative, the MDEQ Surface Water Quality Division (SWQD) identified the Ruddiman Creek watershed as a priority for a contaminated sediment investigation. Figures 1 and 2 depict the Ruddiman Creek watershed. In October 2000, the SWQD, in cooperation with the Army Corps of Engineers, completed a Phase II environmental investigation of Ruddiman Creek under the Corps' Great Lakes Remedial Action Plan technical assistance program. The objective of the Phase II Site Investigation was a preliminary assessment of the nature and extent of impacts to the watershed. Fifty-one locations were sampled throughout the watershed, including locations in the main, west and north branches of Ruddiman Creek, and Ruddiman Pond. Three sediment depth intervals were sampled where possible, for a total of 111 discrete samples (DLZ 2000). Based on the data obtained from these samples, the following conclusions were presented in the Phase II Investigation Report:

  • Ruddiman Pond is impacted with metals, cyanide, semi-volatile organic compounds (SVOCs), volatile organic compounds (VOCs) (one sample), and polychlorinated biphenyls (PCBs) (three samples).

  • The North Branch of Ruddiman Creek is impacted with metals, cyanide, SVOCs, and VOCs.

  • The West Branch of Ruddiman Creek is impacted with metals, cyanide, SVOCs, and VOCs (one sample).

  • The Main Branch of Ruddiman Creek is impacted with metals, cyanide, SVOCs, VOCs, and PCBs.

A comparison of the detected concentrations of these compounds to levels that can cause toxicity to sediment dwelling organisms indicated that metals, SVOCs, and PCBs were the contaminants of concern for ecological effects. Based on the results of the Phase II investigation, the following objectives were identified for future activities (DLZ 2000):

  • Define the horizontal and vertical extent of impacts to the branches of the creek and Ruddiman Pond.
  • Determine the impacts of the storm water to the watershed.
  • Determine the human health effects of exposure to the contaminated sediments.

The MDCH was asked to evaluate the human health risk associated with potential exposures to contaminated sediments in the Ruddiman Creek watershed as part of the efforts to meet the last objective.


DISCUSSION

The Ruddiman Creek watershed is located in an area of dense residential development. The main branch of the creek is located less than 100 feet from several apartment complexes (DLZ 2000). Local members of the Muskegon Lake Remedial Action Plan Public Advisory Committee, Ruddiman Creek Task Force (RCTF) have reported that near-by residents wade, canoe, and fish in the creek. Observed activities on the creek bed include digging for worms (i.e., fish bait), bird watching, and building temporary structures (e.g., children's "forts"). Children play in and around the creek after school, and this is a popular play area in the summer. McGraft Park, a popular suburban park, is located adjacent to Ruddiman Pond. Park users sometimes enter the pond to retrieve lost articles such as hats and balls or other play equipment. Individuals occasionally enter the pond, although steep banks make it less attractive as a play area for children. RCTF members also report that activity around the main branch of Ruddiman Creek does not diminish significantly in the colder months. Ruddiman Pond is a popular area for ice fishing and ice-skating in the winter (Theresa Bernhardt, RCTF Chair, personal communication, 2000).

Human Exposure Pathways

Near-by residents engaging in the activities described above could make direct contact with the creek and pond sediments. Routes of exposure for direct contact include incidental ingestion of and direct dermal contact with sediments. Inhalation of contaminants during these activities is unlikely because the SVOC contaminants of concern are not generally volatile at ambient temperatures. Inhalation of contaminants bound to soil or dust is unlikely due the wet condition of the sediments.

Children have been observed playing in and around the branches of Ruddiman Creek and around Ruddiman Pond. It is unlikely that very young children would be allowed to play unsupervised in all areas of the creek or pond. However, children ages 5 to 9 years as well as older children and adolescents aged 10 to 16 years may play in some areas of the creek especially those in closest proximity to residential developments. Children are likely to frequent these areas several times per week during the summer months and less frequently during colder weather. Two exposure frequencies, 36 and 60 days per year, were used to span the likely range of days that a child might play in the creek area during the warmer months. While children and other individuals might spend time near the creek during colder weather, it is unlikely that significant exposure to contaminants in the creek sediments will occur during these activities.

Environmental Contamination

The ranges of detected concentrations are presented in Tables 1 through 4 for the contaminants of concern identified for each branch of Ruddiman Creek and for Ruddiman Pond (DLZ 2000). Since it is unlikely that people could be exposed to contaminants detected at the deeper sampling intervals, data are presented only for those samples taken from the zero to one-foot depth in the creek and the zero to three-foot depth in the pond. Since sample locations are widely dispersed throughout the watershed, no attempt was made to statistically combine the data.

Tables 1 through 4 also present MDEQ Generic Residential Soil Direct Contact Criteria (DCC) for each contaminant of concern (MDEQ 2000). The DCC are protective of incidental ingestion of and direct dermal contact with soil under a residential exposure scenario. These criteria assume long-term (30 year), frequent exposure (350 days per year); account for the biological availability of contaminants bound to soil; and are developed to be protective of young children (MDEQ 2001). The DCC do not account for differences between soil and sediment that may affect the uptake of contaminants. However, if concentrations in sediments are far less than the DCC, it may reasonably be concluded that contaminant levels do not pose a public health hazard. If sediment concentrations are greater than the DCC, a more detailed site-specific assessment is necessary to determine if exposure could result in adverse effects to human health. Contaminants found in each branch of the creek and in the pond are discussed separately below.

Ruddiman Pond
Of the contaminants detected in sediments at the zero to three-foot depth in Ruddiman Pond, only arsenic and lead exceed the MDEQ residential DCC (Table 1). Other contaminants were found at concentrations up to 10,000 times less than their DCC. Lead was found at a concentration less than twice its DCC. Arsenic was detected at a concentration only slightly more than twice it's DCC. Similar concentrations of arsenic are frequently found in river and lake sediments because the higher organic content of these media bind and hold the arsenic in place. The binding ability of sediments also makes the arsenic found in these media less biologically available. When a person is exposed to arsenic in sediments, less of the contaminant will be absorbed into the body. Direct exposure to pond sediments will be infrequent and it is unlikely that exposure to lead and arsenic in the pond sediments could result in adverse human health effects.

West Branch of Ruddiman Creek
Of the contaminants detected in sediments at the zero to one-foot depth in the west branch of Ruddiman Creek, only benzo(a)pyrene and lead exceed the MDEQ residential DCC (Table 2). Other contaminants were found at concentrations up to 10,000 times less than their DCC. Benzo(a)pyrene was detected in only one sample, and at a concentration less than twice the DCC. Lead was detected throughout the west branch, but at levels less than twice the DCC. Since the frequency of exposure to the creek sediments is likely to be far less than was assumed for the development of the DCC, it is unlikely that exposure to these levels of contaminants could result in adverse human health effects.

North Branch of Ruddiman Creek
Of the contaminants detected in sediments at the zero to one-foot depth in the north branch of Ruddiman Creek, only benzo(a)pyrene, arsenic, and lead exceed the MDEQ residential DCC (Table 3). Other contaminants were found at concentrations up to 10,000 times less than their DCC. Benzo(a)pyrene was detected at a concentration slightly more than twice its DCC. Arsenic and lead were detected at concentrations less than twice their DCC. For the reasons discussed above, it is unlikely that exposure to these contaminants in creek sediments could result in adverse human health effects.

Main Branch of Ruddiman Creek
Benzo(a)pyrene, arsenic, lead, and PCB 1260 were detected in sediments at the zero to one foot depth in the main branch of Ruddiman creek at levels exceeding the MDEQ residential DCC (Table 4). Arsenic was detected at concentrations less than twice its DCC. Benzo(a)pyrene was detected at concentrations up to three and a half times its DCC. However, most detections of benzo(a)pyrene were at concentrations less than twice the DCC. It is unlikely that exposure to arsenic and benzo(a)pyrene in creek sediments could result in adverse human health effects.

Lead was detected consistently throughout the sediments in the main branch of the creek at concentrations two to three times its DCC. PCB 1260 was detected in two areas of the main branch of the creek at concentrations up to almost six times its DCC. The area of highest PCB concentration is less than 100 feet from several apartment complexes and an elementary school. Children may be particularly sensitive to the adverse health effects of lead and PCBs. Therefore, a child/adolescent receptor, ages 10 to 16, was used to estimate the dose of PCB and lead to a child playing in and around the main branch of the creek. The potential for adverse health effects from exposure to PCBs and lead in the creek sediments is discussed below.

Toxicological Evaluation

The potential for adverse health effects that might result from exposure to contaminated media is evaluated by estimating a dose of each contaminant of concern. These doses are calculated for scenarios in which individuals might come into contact with the contaminated media. In order to calculate these doses, assumptions are made about the way people behave, the amount of contaminated media they may ingest, inhale, or make skin contact with, and how long and how frequently they may make contact with the contaminated media. Table 5 presents the exposure assumptions used to calculate intake doses for children playing in the creek. These calculated doses are then used along with chemical-specific toxicological information to evaluate the risk of noncancer and cancer health effects.

PCBs
Noncancer effects
In order to assess the potential for noncancer health effects, estimated doses are compared to an Agency for Toxic Substances and Disease Registry (ATSDR) minimal risk level (MRL) or the U.S. Environmental Protection Agency's (EPA's) oral reference dose (RfD). MRLs and RfDs are doses below which noncancer adverse health effects are not expected to occur. They are derived from toxic effect levels obtained from human population and/or occupational studies, and laboratory animal studies. Toxic effect levels identified from these studies may be either a no observed adverse effect level (NOAEL), or the lowest observed adverse effect level (LOAEL). Since the NOAEL is the highest dose that does not result in any adverse health effects, this effect level is preferred as the basis for an MRL or an RfD. The LOAEL is the lowest dose at which adverse health effects are seen, and is used when a NOAEL cannot be identified.

Because there is uncertainty in both human and animal studies, NOAELs and LOAELs are divided by "uncertainty factors" to derive the more protective RfD or MRL. These uncertainty factors are generally in multiples of ten, but may sometimes be less depending on the quality of the study or the seriousness of the observed adverse effect. An additional uncertainty factor is applied when an RfD or MRL is based on a LOAEL.

Given the level of uncertainty in the development of RfDs and MRLs, they should not be considered as a strict line between a safe and an unsafe dose. If a calculated dose exceeds either the RfD or the MRL, it is important to consider the magnitude of the exceedance as well as the uncertainty surrounding the calculated dose before determining if noncancer health effects are likely.

The ATSDR has developed an oral chronic MRL of 0.02 micgrograms per kilogram per day (ug/kg-day) based on immunological effects in adult monkeys exposed to PCBs for up to 4 and 1/2 years. The MRL is supported by human data that suggests a NOAEL of 0.05 ug/kg-day for neurobehavioral developmental effects in human offspring. This is a dose at which no significant developmental effects were observed in human infants. If the human NOAEL were divided by an uncertainty factor of 3, the resulting MRL would be equal to the MRL of 0.02 ug/kg-day based on animal studies (ATSDR 2000).

Two exposure scenarios were used to estimate the dose of PCB that could be received by a child/adolescent playing in and around the main branch of Ruddiman Creek in the area of the highest detected PCB concentrations. The dose of PCBs that could be received by a child ages 5 to 9 years ranged from 0.037 ug/kilogram of body weight - day (ug/kg-day) for an exposure frequency of 36 days/year to 0.062 ug/kg-day for an exposure frequency of 60 days/year. The dose of PCBs that could be received by a child or adolescent ages 10 to 16 years ranged from 0.027 ug/kg-day for an exposure frequency of 36 days/year to 0.046 ug/kg-day for an exposure frequency of 60 days/year. The calculated dose for both age groups under both exposure scenarios exceeds the ATSDR MRL discussed above. The calculated dose for a child ages 5 to 9 under the 60-day/year exposure scenario exceeds the NOAEL for developmental effects in human offspring.

Cancer Risk
Cancer risk is estimated by calculating a dose and multiplying it by a cancer potency factor, known as the cancer slope factor. Some cancer slope factors are derived from human population or occupational studies. Most of these studies are of individuals, such as occupational groups, that are exposed at higher levels than the general population.

When no human data are available, cancer slope factors are calculated from data obtained from animal studies in laboratories. The dose of contaminant to which animals are exposed in the laboratory is generally far higher than would result from environmental exposures and animals are exposed to chemicals throughout their life spans. Use of animal data, therefore, introduces uncertainty into the cancer slope factor due to differences in metabolism, life span, and body size between test animals and humans. Differences in exposure patterns, for example continuous vs. intermittent exposure, introduce additional uncertainty.

For most cancer causing chemicals (carcinogens), it is generally thought that an increasingly lower dose will result in a proportionally lower cancer risk. The cancer slope factor quantitatively defines this relationship between the dose and the risk of developing cancer. In order to calculate the slope factor, it is necessary to extrapolate high doses from either human or animal studies to lower, more realistic levels of exposure. Extrapolation below the observed dose level introduces uncertainty into the cancer slope factor. Cancer risk estimates are, therefore, measures of the chance of developing cancer as a result of exposure to an estimated dose. Cancer risk estimates are generally expressed as the number of individuals in a larger population that may develop cancer. Note that these estimates are for excess cancers that might occur as a result of exposure to contaminants at this site in addition to those that would be expected in an unexposed population. Cancer is a common illness. A population with no known exposure to chemical contaminants could be expected to have a substantial number of cancer cases.

This consultation describes cancer risk qualitatively using terms like moderate, low, very low and no significant increase in cancer risk. The table below shows the relationship between the quantitative estimates of cancer risk calculated based on site-specific exposures and the qualitative term used to describe the risk.

Quantitative Risk Qualitative Term
1 in 1,000,000 No increased risk
1 in 100,000 Very low increased risk
1 in 10,000 Low increased risk
1 in 1,000 Moderately increased risk
1 in 100 High increased risk
1 in 10 Very high increased risk

A cancer slope factor for PCBs of 2.0 (mg/kg-day)-1 is recommended by the EPA for assessing the cancer risk associated with ingestion of contaminated soil or sediments, or when assessing early-life exposures. This slope factor is based on an increased incidence of liver tumors in female rats exposed to a mixture of PCBs over their lifetime. Based on this slope factor, a child ages 5 to 9 would have a low to very low increased risk of developing cancer as a result of exposure to the highest levels of PCBs in the main branch of Ruddiman Creek. A child/adolescent ages 10 to 16 would have a very low increased risk of developing cancer as a result of exposure to these levels of PCBs at both the 36 and 60 day/year exposure frequency.

There are several factors that contribute to the uncertainty surrounding the estimated dose of PCBs. (1) It was assumed that a child would be exposed to PCBs at the highest detected concentration of PCBs in the main branch of the creek. PCB concentrations vary throughout the watershed, however large stretches of the creek have not been sampled and PCB concentrations in these areas could be either lower or higher. However, the highest detected concentrations of PCBs were found in an area less than 100 feet from several apartment complexes and the Glenside Elementary School. (2) Assumptions were made about the bioavailability of PCBs in sediments based on information about the behavior of PCBs in soil. PCBs may be more or less bioavailable due to the increased moisture and organic content of sediments as compared to soil. (3) Assumptions were made about the way children behave and how often they will play in the creek sediments that may vary from one child to the next. (4) It was assumed that children were not exposed to PCBs from any other source. Local residents fish in the Ruddiman watershed. There are no data concerning PCB concentrations in fish in Ruddiman Creek; however, the MDCH has issued a fish advisory for Muskegon Lake based on PCB contamination (MDCH 2001). If children are eating contaminated fish, their dose of PCBs will be greater than that estimated for exposure to the impacted sediments alone.

Given the uncertainties discussed above, most importantly the lack of data for several areas of the creek, the PCB contamination in the main branch of Ruddiman Creek may present a public health hazard for children and adolescents playing in and around the creek. More data is needed so that a more thorough assessment can be conducted.

Lead
Although there is a great deal of information concerning the adverse health effects of lead exposure in humans, neither an MRL nor an RfD is available. The level of lead in the body, usually expressed as blood levels, is used to determine the potential for adverse health effects rather than an external dose in mg/kg-day. This approach is used for lead because exposure can occur from several different sources including air, food, water, and soil contamination. It is therefore difficult to determine the source and the external dose in human populations exhibiting adverse health effects as result of exposure to lead. Models that account for multiple exposures to lead are often used to assess potential effects from exposure to lead in the environment. However, these models are not generally recommended for children over seven years of age (ATSDR 1999). Given the available information, it is not possible to determine if children could experience adverse health effects as a result of exposure to the levels of lead found in the main branch of Ruddiman Creek.

Addressing the Unique Vulnerabilities of Children

Children may be at greater risk than adults from certain kinds of exposure to hazardous substances at sites of environmental contamination. They engage in activities such as playing outdoors and hand-to-mouth behaviors that increase their exposure to hazardous substances. They are shorter than an adult, which means they breathe dust, soil, and vapors close to the ground. Their lower body weight and higher intake rate results in a greater dose of hazardous substance per unit of body weight. The developing body systems of children can sustain permanent damage if toxic exposures are high enough during critical growth stages.

This assessment used MDEQ criteria protective of young children (MDEQ 2000, 2001) to determine if contaminants detected in the Ruddiman Creek watershed are a public health hazard. Where contaminant concentrations exceeded these criteria, doses were estimated for a child/adolescent and compared to health effect levels protective of children. Children may be sensitive to the effects of PCBs. Studies of young animals prenatally exposed indicate that PCBs can cause developmental effects. Studies of human infants whose mothers ate fish contaminated with PCBs while pregnant suggest that these developmental effects may also occur in human offspring (ATSDR, 2000). Young children, particularly those under the age of five years, are also particularly sensitive to the neurodevelopmental effects of lead. However, very young children are unlikely to be exposed to sediments in the watershed. It is not possible to determine if older children could be adversely affected by the levels of lead found in the main branch of Ruddiman Creek.


CONCLUSIONS

  1. No apparent public health hazard exists for children and adolescents playing in Ruddiman Pond, or the north and west branches of Ruddiman Creek.

  2. An indeterminate public health hazard exists for children and adolescents playing in the main branch of Ruddiman Creek. Once additional data are collected, a more thorough assessment will be conducted. The area between Glenside Avenue and Barclay Road is of particular concern due to the high concentrations of PCBs detected there, and the proximity to residential housing and the Glenside Elementary School. These conclusions are based on the preliminary data presented in the Phase II ESA and may change as additional sampling data become available.

RECOMMENDATIONS

  • Conduct additional sampling to fully identify the levels of contaminants and the extent of contamination in the Ruddiman watershed sediments.

  • Characterize contaminant levels in fish in the Ruddiman watershed.

  • Conduct community education to inform nearby residents of the potential risks of exposure to the contaminants in the creek sediments.

  • Post warning signs on the main branch of Ruddiman Creek where children are likely to play.

PUBLIC HEALTH ACTION PLAN

  • Additional sampling should be conducted by the MDEQ in cooperation with the Army Corps of Engineers and the RCTF. The sampling plan should be designed to fully characterize contaminants in the sediments and fish in the watershed. MDCH will review this data in a future health consultation.

  • The RCTF has made several public education presentations at the nearby elementary school. The MDCH encourages the RCTF to continue these efforts and will be available to assist in these presentations if needed.

  • The MDEQ should take the primary responsibility for posting warning signs on the main branch of Ruddiman Creek where children are likely to play. The MDCH recommends that the RCTF be consulted on the content of the message and the location for posting. The MDCH will be available to assist if needed.

The MDCH will be available to consult on the appropriateness and efficacy of future remedial actions.

If any citizen has additional information or health concerns regarding the Ruddiman Creek Watershed site, please contact the Michigan Department of Community Health, Division of Environmental and Occupational Epidemiology, at 1-800-648-6942.


REFERENCES

ATSDR (Agency for Toxic Substances and Disease Registry). 1999. Toxicological Profile for Lead. July 1999.

ATSDR (Agency for Toxic Substances and Disease Registry). 2000. Toxicological Profile for Polychlorinated Biphenyls. November 2000.

DLZ Michigan Inc. 2000. Phase II Site Investigation Report, Ruddiman Creek, Muskegon, Michigan. October 2000.

EPA (United States Environmental Protection Agency). 1998. Risk Assessment Guidance for Superfund Volume I: Human Health Evaluation Manual Supplemental Guidance Dermal Risk Assessment Interim Guidance. Peer Consultation Workshop Draft. November 6, 1998.

EPA (United States Environmental Protection Agency). 2000. Child-Specific Exposure Factors Handbook. External Review Draft. June 2000.

MDCH (Michigan Department of Community Health). 2001. 2001 Michigan Fish Advisory.

MDEQ (Michigan Department of Environmental Quality). 2000. Memorandum to ERD staff, subject: Interim Environmental Response Division Operational Memorandum #18: Part 201 Generic Cleanup Criteria Tables. June 7, 2000. At http://www.michigan.gov/deq/0,1607,7-135-3311_4109_9846-20527--,00.html.

MDEQ. (Michigan Department of Environmental Quality). 2001. Environmental Response Division. Part 201 Generic Soil Direct Contact Criteria: Technical Support Document. January 5, 2001.


Location Map
Figure 1. Location Map

Location of Features
Figure 2. Location of Features


PREPARERS OF THE REPORT

Michigan Department of Community Health
Division of Environmental and Occupational Epidemiology

Linda D. Larsen, Ph.D.
Toxicologist, Section Manager
Toxicology and Response Section

Robin Freer, M.A.
Geographic Information System Specialist
Toxicology and Response Section


ATSDR Regional Representative

Mark Johnson
Office of Regional Operations, Region V


ATSDR Technical Project Officer

Alan W. Yarbrough
Division of Health Assessment and Consultation
Superfund Site Assessment Branch


CERTIFICATION

This Ruddiman Creek Health Consultation was prepared by the Michigan Department of Community Health under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the health consultation was begun.

Alan W. Yarbrough
Technical Project Officer, SPS, SSAB, DHAC, ATSDR


The Division of Health Assessment and Consultation, ATSDR, has reviewed this public health consultation and concurs with the findings.

Roberta Erlwein
Chief, State Program Section, SSAB, DHAC, ATSDR


Table 1. Range of chemical concentrations detected in sediments in Ruddiman Pond.

Chemical Range of detected concentrations 0-3 foot depth* ug/kg MDEQ Residential Soil Direct Contact Criteria ug/kg
  minimum maximum  
Semi-volatile organic compounds      
Anthracene ND ND 230,000,000
Benzo(a)anthracene ND 1,100 20,000
Benzo(a)pyrene ND 880 2,000
Chrysene ND 1,300 2,000,000
Dibenzo(a,h)anthracene ND ND 2,000
Fluoranthene ND 2,600 46,000,000
Flourene ND ND 27,000,000
Naphthalene ND ND 16,000,000
Phenanthrene ND 1,500 1,600,000
Metals      
Arsenic 420 19,000 7,600
Cadmium 130 29,000 550,000
Chromium 5,500 3,200,000 790,000,000
Copper 2,500 340,000 20,000,000
Lead 6,300 630,000 400,000
Mercury ND 700 160,000
Nickel 2,200 63,000 40,000,000
Zinc 12,000 750,000 170,000,000
Other      
PCB 1260 ND 190 1,000

ND = Compound was not detected.

References: DLZ 2000, MDEQ 2000

Shaded values are greater than the MDEQ residential soil direct contact criterion.

*Depth in feet below surface of the pond bottom.


Table 2. Range of chemical concentrations detected in sediments in the West Branch of Ruddiman Creek.

Chemical Range of detected concentrations 0-1 foot depth* ug/kg MDEQ Residential Soil Direct Contact Criteria ug/kg
  minimum maximum  
Semi-volatile organic compounds      
Anthracene ND ND 230,000,000
Benzo(a)anthracene ND 3,400 20,000
Benzo(a)pyrene ND 3,800 2,000
Chrysene ND 4,400 2,000,000
Dibenzo(a,h)anthracene ND ND 2,000
Fluoranthene ND 9,000 46,000,000
Flourene ND ND 27,000,000
Naphthalene ND 3,400 16,000,000
Phenanthrene ND 4,900 1,600,000
Metals      
Arsenic ND 8,200 7,600
Cadmium 490 5,400 550,000
Chromium 10,000 64,000 790,000,000
Copper 32,000 170,000 20,000,000
Lead 30,000 460,000 400,000
Mercury ND 540 160,000
Nickel ND 56,000 40,000,000
Zinc 87,000 780,000 170,000,000
Other      
PCB 1260 ND ND 1,000

ND = Compound was not detected.

References: DLZ 2000, MDEQ 2000

Shaded values are greater than the MDEQ residential soil direct contact criterion.

*Depth in feet below surface of the pond bottom.


Table 3. Range of chemical concentrations detected in sediments in the North Branch of Ruddiman Creek.

Chemical Range of detected concentrations 0-1 depth* ug/kg MDEQ Residential Soil Direct Contact Criteria ug/kg
  minimum maximum  
Semi-volatile organic compounds      
Anthracene ND 2,600 230,000,000
Benzo(a)anthracene 530 9,600 20,000
Benzo(a)pyrene 570 4,200 2,000
Chrysene 670 11,000 2,000,000
Dibenzo(a,h)anthracene ND 1,400 2,000
Fluoranthene 1,300 26,000 46,000,000
Flourene ND 2,400 27,000,000
Naphthalene ND 1,700 16,000,000
Phenanthrene 780 25,000 1,600,000
Metals      
Arsenic 1,000 11,000 7,600
Cadmium 320 3,900 550,000
Chromium 9,900 48,000 790,000,000
Copper 12,000 100,000 20,000,000
Lead 30,000 590,000 400,000
Mercury ND 440 160,000
Nickel 7,100 26,000 40,000,000
Zinc 8,400 580,000 170,000,000
Other      
PCB 1260 ND ND 1,000

ND = Compound was not detected.

References: DLZ 2000, MDEQ 2000

Shaded values are greater than the MDEQ residential soil direct contact criterion.

*Depth in feet below surface of the pond bottom.


Table 4. Range of chemical concentrations detected in sediments in the Main Branch of Ruddiman Creek.

Chemical Range of detected concentrations 0-1 depth* ug/kg MDEQ Residential Soil Direct Contact Criteria ug/kg
  minimum maximum  
Semi-volatile organic compounds      
Anthracene ND 4,100 230,000,000
Benzo(a)anthracene ND 6,800 20,000
Benzo(a)pyrene ND 7,000 2,000
Chrysene ND 9,900 2,000,000
Dibenzo(a,h)anthracene ND 2,200 2,000
Fluoranthene 470 27,000 46,000,000
Flourene ND 3,200 27,000,000
Naphthalene ND 1,700 16,000,000
Phenanthrene 340 30,000 1,600,000

Metals

     
Arsenic 780 12,000 7,600
Cadmium 510 200,000 550,000
Chromium 24,000 5,900,000 790,000,000
Copper 16,000 480,000 20,000,000
Lead 7,100 1,100,000 400,000
Mercury ND 2,000 160,000
Nickel 6,300 160,000 40,000,000
Zinc 91,000 1,400,000 170,000,000

Other

     
PCB 1260 ND 5,800 1,000

ND = Compound was not detected.

References: DLZ 2000, MDEQ 2000

Shaded values are greater than the MDEQ residential soil direct contact criterion.

*Depth in feet below surface of the pond bottom.


Table 5. Exposure parameters used for intake equations.

Exposure Parameter Ages 5-9 Ages 10-16
Duration in years 5 7
Frequency in days/year 36 or 60 36 or 60
Body weight in kilograms 25 52
Soil Ingestion Rate1 in milligrams (mg) /day 100 100
Oral absorption efficiency2 (unitless) 50 % 50 %
Skin surface area1 in square centimeters (cm2) 4,200 6,600
Dermal adherence factor3 in mg/cm2 2.7 2.7
Dermal absorption efficiency2 (unitless) for PCBs 0.14 0.14

1 EPA 2000
2 MDEQ 2000
3 EPA 1998


ATTACHMENT A: RESPONSIVENESS STATEMENT

Comment: Page 1, Paragraph 2, First Sentence: Suggest changing this to read "based on existing sediment chemistry data, no apparent public health hazard exists for the sediments in Ruddiman Pond, or the north and west branches of Ruddiman Creek.

Response: The suggested change has been made.

Comment: Page 2, first Bullet: Suggest changing this to read, "Ruddiman Pond is impacted with metals, cyanide, semi-volatile organic compounds (SVOCs), volatile organic compounds (VOCs) (one sample), and polychlorinated biphenyls (PCBs) (three samples).

Response: The suggested change has been made.

Comment: Page 9: This page refers to the Bendix/Allied Automotive NPL site (which is not in the Ruddiman Creek watershed).

Response: This error has been corrected.

Comment: We were not sure what the scientific basis was for being concerned with compounds that routinely exceeded twice their DCC.

Response: It was not intended to imply that exceedance of twice the DCC for an individual compound would engender concern for human health effects. Rather, the DCC were used as a preliminary screen to determine which compounds would require further detailed analysis in the Health Consultation.

Comment: Children exposed to contaminated sediments in the main branch of Ruddiman Creek were estimated to receive a dose of 0.02 ug/PCB/kg/d. It is unclear what body weight, amount of sediment consumed, amount of PCBs absorbed through the skin and frequency of exposure were used in the calculations.

Response: Table 5, which includes this information, has been added to the Consultation.

Comment: The assessment concludes that children have a low increased risk of developing cancer as a result of exposure to PCBs. The slope factor used to calculate the potential risks was not provided in the report. One uncertainty not mentioned in the report is that the slope factor for PCBs is based on a life time exposure to laboratory animals so there is uncertainly in extrapolating from a long-term exposure in rodents to a sporadic short-term exposure in humans.

Response: The cancer slope factor for PCBs used in the Consultation has been provided and additional discussion of uncertainty has been added.

Comment: The assessment concludes that the main branch of Ruddiman Creek presents a health hazard to children. This conclusion is based primarily on a comparison between the estimated dose of PCBs that children receive at the site and the Minimum Risk Level (MRL) of 0.02 ug/kg/d developed by the ATSDR (2000) and the No Observed Adverse Effect Level (NOAEL) of 0.05 ug/Kg/d for neurobehavioral effects in human offspring. The assessment states that this is a preliminary assessment and that more samples need to be collected in order to do a complete assessment. It may be more accurate to state that the main branch of Ruddiman Creek may pose a public health hazard to children and that once additional data are collected a more thorough assessment will be conducted.

Response: The suggested change has been made to the third paragraph on page 7.

Comment: Calculations should be based on a range of exposure, including worse case exposure and ranging to the conservative exposures included in the draft Health Consultation. The worse case exposures determined by the technical committee are the following: 12 weeks at 5 days/week for 6 hours/day; and, 40 weeks at 2 days/week for 2 hours/day.

Response: A range of exposure frequency from 36 to 60 days/year has been used in the final Consultation to assess exposures for children/adolescents playing the creek. The additional exposure for 40 weeks at 2 days/week for 2 hours/day was not included in the assessment. Activities in the creek area during the colder months are not likely to result in significant exposure to contaminated sediments as would be expected during the warmer months when children would be expected to make direct contact with sediments wearing minimal clothing.

Comment: There was some question as to whether a residential exposure of one day is calculated based on the OSHA standard of 8 hours per day.

Response: The residential exposure scenario is not adjusted for the number of hours per day that exposure may occur. The intake rates for both the incidental ingestion and dermal exposure pathways are assumed to occur over the entire 24 hour day. For the incidental ingestion pathway, it has essentially been assumed that all 100 mg/day of soil ingested over the course of the day comes from contaminated sediments. While only a single dermal exposure event is assumed per day, the basis for the dermal absorption efficiency essentially assumes that contaminated soil remains on the skin for 24 hours without washing. In this way, conservatism is built into the calculations and it may safely be assumed that exposure is not underestimated and may in fact be significantly overestimated.

Comment: Calculations should be run for the age groups of 5 to 9 years in addition to the 10 to 16 year group already analyzed.

Response: A 5 to 9 year-old receptor has been added to the calculations.

Comment: An emphasis should be placed on the fish analysis for metals and PCBs.

Response: Fish samples have been taken from Ruddiman Creek and Pond and these results will be addressed in an additional Health Consultation.


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