2. Materials and methods
2.1. Participants and sampling
The present study is part of a larger project aimed to evaluate
environmental and health effects of extracting and processing Mn mining
product. Details concerning sampling design, geographical, population
and sociodemographical data, and mining activity on the zone can be
found in Rodriguez-Agudelo et al. (2006).
We selected 300 people by means of a random multi-step procedure. At
the moment of sampling, they lived in 8 different communities at different
distances, ranging between 0.5 and 7.4 km, from the mining and refining
plants on an irregular mountainous zone called ‘‘Sierra Madre Oriental’’.
All of the participants from the different communities were informed
about the objectives of this study and agreed to collaborate. Inclusion
criteria were age 20–85-year old, either men or women (selection was made
to be representative for the communities both, in age and gender); living
for at least 5 years in the community at sampling moment. Houses of
participants were selected randomly and then inhabitants were visited to
invite participants to this study. The list of participants was compared
with the local census to obtain a final list of subjects to match
sociodemographic characteristics of population. Exclusion criteria consisted
in miners and ex-mine workers. People suffering from diabetes,
liver-related or psychiatric diseases were also excluded. All of the
participants from the different communities were informed about the
objectives of this study and agreed to collaborate.
Blood samples were taken from cubital venous blood in metal-free
Vacutainer EDTA tubes to measure blood Mn as well as other
biomarkers: prolactin, hemoglobin and lead.
The present study was approved by the bioethics committee of our
institution.