1. Students should be familiar with the health effects
of arsenic poisoning from earlier classes. Start
class by presenting the following scenario to
Diaz lives with her family in rural Arizona.
She has lived there for about 15 years. Recently
she visited her doctor’s office with
complaints about a skin affliction on her
hands and feet. She has hyperpigmentation
(dark spots) and keratoses over her hands
and feet. The doctor asks her about when these
symptoms started appearing. Monica isn’t
able to identify when the keratoses exactly
started, perhaps a couple of months ago, but
the black spots began appearing more recently.
The doctor takes some blood work and asks
her about her occupational environment and
her water supply. Where does she get her water
from? What type of environment does she live
in, what does she have contact with, and what
does she do?What do they think is wrong with
the patient? They should use the background
they’ve gained from previous classes
to justify their reasoning. Why might the
doctor be asking the questions about environment
and water source? What other information would
the doctor need to ask or find out?
2. Review the scenario with students and point out the
evidence for arsenic poisoning.
3. Ask students how much arsenic can be in the water
and yet still be safe to drink. Students will have been
exposed to this in earlier lessons.
4. Review what the health risks of arsenic in drinking
5. Review the national (EPA) and worldwide (WHO) standards
for arsenic levels in drinking water.
6. Present the following scenario to students: Health
issues of local people in this Chilean area.
In the Elqui watershed there is an increased prevalence
of bladder and skin cancers, even among adolescents.
Many of the people have skin keratoses, and hyperpigmentation.
7. Students should recognize the similarities between
the scenario that they reviewed at the beginning of
class and this scenario. Explain that public health
officials have pinpointed arsenic as the probable cause
of the ailments. However, where is the arsenic coming
from? While the data from water close to the mine indicates
that there are significant amounts of arsenic in this
water source, there is data from other areas within
the watershed with high levels of arsenic. Is the mine
responsible for the high levels of arsenic in the water?
8. Present raw data given in Figure
1 and the map #1. Explain to students that drawing upon
the past lessons will help them determine where the
arsenic is coming from. Direct students to place the
raw data on map #1 which shows the geology.
9. Students are given the map data. Students postulate
what they think is happening.
10. Students are presented with additional information such
as increased erosion due to the weather phenomenon
known as El Nino, and increased
amounts of arsenic in the water as a result of mining
processes. Students read the abridged version
of the actual article provided and respond to questions.
11. Using the data and research paper, students
write a paper as if reporting back to the community
leaders and health officials. Included should be a description
of the problem and the suspected origin
of the problem. Can it be attributed to the mines
or are other factors responsible? Students make
a recommendation in their papers for action to be taken
for reducing risks. Students should also include
some of the maps and data points they correlated
to within their reports.
knowledge of health impacts of arsenic can be assessed
in their spoken responses to the first scenario. If
students are able to analyze data and draw conclusions,
this can be assessed in their articulation of a possible
relationship between arsenic and gold deposits in a
written statement. If students are able to use real
data to determine the source of the arsenic in the
drinking water and present that in a written format,
this can be assessed in the written report.