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6.27 Calculate a risk-based groundwater protection standard (in ppb) for the chemical
1,2-dichloroethane for a residential homeowner where the person’s well used for drinking
water is contaminated with 1,2-dichloroethane. Assume you are determining risk for an
average adult who weighs 70 kg. The state where you work has determined that an
acceptable risk is 1 cancer occurrence per 106 people. Use the values for route of intake,
exposure frequency, exposure duration, and averaging time provided for residential use in
Table 6.14. Assume an oral slope factor for 1,2-dichloroethane of 9.2 × 10-2 per
(mg/kg)/day.
Solution:
6.28 Determine if exposure by oral ingestion to the chemicals xylene, toluene, arsenic,
and hexavalent chromium poses a noncarcinogenic health risk. The chemical specific
reference doses (mg/kg-day) obtained from IRIS are: xylene (0.2), toluene (0.8), arsenic
(0.0003), and hexavalent chromium (0.003) Assume a 70 kg individual consumes 2 liters
of water per day with these chemicals dissolved at a concentration of 1 mg/L.
Solution:
6.29 A commercial area had its own separate groundwater supply system that provided
drinking water. Unfortunately the groundwater was contaminated with arsenic at a
concentration of 10 ppb. The property owner placed a deed restriction on accessing the
groundwater and also contacted the city to complete a hookup with the city water supply.
Determine if exposure by oral ingestion to the chemical arsenic poses a noncarcinogenic
health risk for individuals consuming drinking water after the property owner’ actions
have taken place. Assume a 70 kg individual consumes 2 liters of water per day and the
reference dose for arsenic is 0.0003 mg/kg-day.
Solution:
6.30 (a) Calculate a risk-based groundwater protection standard for the chemical
benzo(a)pyrene. Assume you are determining risk for an average adult female who
weighs 50 kg and consumes 2 L water and eats 30 g fish per day. The state has
determined that an acceptable risk is 1 cancer occurrence per 105 people. Use the values
for exposure frequency, exposure duration, and averaging time provided for residential
land use. (b) According to EPA’s Integrated Risk Information System (IRIS), what type
of carcinogen is benzo(a)pyrene, using the weight of evidence of human and animal
studies? (c) Assuming the chemical is leaching from some contaminated soil, estimate the
allowable concentration of benzo(a)pyrene in the pore water of contaminated soil.
Solution:
6.31 Is there an unsafe risk associated with a 70 kg adult eating 15 g fish every day that
contains 1 mg/kg of methylmercury? Methylmercury has been shown to cause
developmental neuropsychological impairment in human beings. The RfD for
methylmercury is 1 × 10-4 mg/kg-day.
Solution:
6.32 Is there an unsafe risk associated with a 70 kg adult eating 15 g fish every day that
contains 9.8 µg/ kg of Arochlor 1254? Arochlor 1254 can exhibit noncarcinogenic effects
in humans. Use the IRIS database to find any other information required to solve this
problem.
Solution:
6.33 Concentrations of toxaphene in fish may impair human health and fish-eating birds
(such as bald eagles) that feed on the fish. (a) If the log of the octanol–water partition
coefficient (log Kow) for toxaphene is assumed to equal 4.21, what is the expected
concentration of toxaphene in fish? (Assume that the equilibrium aqueous phase
toxaphene concentration is 100 ng/L.) (b) If it is assumed that an average person drinks 2
L untreated water daily and consumes 30 g contaminated fish, what route of exposure
(drinking water or eating fish) results in the greatest risk from toxaphene in 1 year? (c)
What route of exposure is greatest for a higher-risk group that is assumed to consume 100
g fish per day? Support all of your answers with calculations. Assume the following
correlation applies to toxaphene and our problem’s specific fish:
ow
log BCF 0.85log 0.07K= −
Solution:
6.34 Identify a brownfield in your local community, hometown, or a nearby city. What
was specifically done at the site? What are several social, economic, and environmental
issues associated with restoring the brownfield site?
Solution:
Students’ responses will vary.
6.35 The Code of Federal Regulations (CFR) is the codification of the general and
permanent rules published in the Federal Register by the executive departments and
agencies of the Federal Government. It can be accessed at http://www.gpoaccess.gov/cfr/.
What CFR number is associated with the following sections? (for example, 50 CFR for
Wildlife and Fisheries). (a) Protection of Environment; (b) Transportation, (c)
Conservation of Power and Water Resources, (d) Public Health, and (e) Highways.
Solution:
6.36 Research the safety of your personal care and household cleaning products using a
web site such as http://lesstoxicguide.ca/index.asp?fetch=personal. Develop a table that
lists 7 current personal care or household cleaning products used in your apartment,
home, or dormitory. Add a second column that lists a less hazardous alternative for each
of the 7 products.
Solution:
Students’ responses will vary but an example table is listed below.
Product
Non-hazardous alternative
1. Crest toothpaste
1. Arm and Hammer Teeth Whitening Booster
Toothpaste
2. Garnier Fructis hair conditioner
2. Dr. Bronner’s Magic Organic Citrus Hair Rinse
3. OB non-applicator tampons
3. Diva cup
4. Garnier fructis hair gel
4. Aloe vera gel
5. Oil of Olay Face Cream
5. Shea butter
6. ACT fluoride rinse
6. Tom’s of Main Natural Baking Soda
Mouthwash
7. Tom’s of Main Natural
Deodorant
7. Make your own recipe with cornstarch
6.37 Do some background research. Some good places to look for this and related
information include EXTOXNET, the National Toxicology Program (NTP), the Agency
for Toxic Substances and Disease Registry (ATSDR), and the National Library of
Medicine (choose one). (a) Is atrazine bioaccumulative and/or persistent in the
environment? Explain your answer. (b) Now consider applying atrazine to your lawn
and assume that there are children in the household and they like to eat grass, dirt, and
worms while playing on grass. Assume the atrazine is both bioaccumulative and
persistent. How does this new information about the partitioning and persistence
behavior of atrazine affect your consideration of the potential toxicity of atrazine to
humans?
Solution:
