Protocols for Environmental and Health Assessment of Mercury Released By Artisanal and Small Scale Gold Miners

293 Pages·2006·12.99 MB·English

by  United Nations

Project EG/GLO/O 1/ G3 4
Removal of Barriers to Introduction of Cleaner Artisanal Gold Mining and
Extraction Technologies
Protocols for Environmental and Health Assessment of Mercury
Released by Artisanal and Small-Scale Gold Miners
Global Mercury Project, Coordination Unit
Pablo Huidobro, Project Manager, UNIDO
Marcello M. Veiga, Chief Technical Advisor, UNIDO
Svitlana Bogoslavska, Administrative Assistant, UNIDO
Primary Authors
Marcello M. Veiga
University of British Columbia, Dept. Mining Engineering
6350 Stores Rd., Vancouver, BC, V6T 124, Canada
Randy F. Baker
Azimuth Consulting Group
218-2902 W. Broadway Ave., Vancouver, BC, V6K 2G8, Canada
Editing: Marvin B. Fried and Denise Withers
Covers: Jogo Pedro Veiga using UNIDO photographs from Venezuela and
Lao PDR
Disclaimer: The designations employed and the presentation of the material
in this document do not imply the expression of any opinion whatsoever of
the Secretariat of the United Nations Industrial Development Organization
(UNIDO) concerning the legal status of any country, territory, city or area of
its authorities, or concerning the delimitation of itsfiontiers or boundaries.
Mention of company names and commercial products does not imply the
endorsement of WIDO.
Protocols for Environmental and Health Assessment of Mercury
Released by Artisanal and Small-scale Gold Miners
Global Mercury Project
UNIDO, Vienna International Center
P.O. Box 300
A- 1400 Vienna, Austria
www.globalmercury.org
Children and women are main victims of the misuse of mercury by
artisanal gold miners
Protocols for Environmental and Health Assessment of Mercury
Released by Artisanal and Small-scale Gold Miners1M.M. Veiga,
R.F. BakerIVienna, Austria: GEFIUNDPIUNIDO, 2004,289~.
1. mercury pollution, 2. artisanal gold mining, 3. environmental
and health assessment, 4. monitoring methods.
ISBN 92- 1- 106429-5 UNIDO ID: ID1422
UN Sales No.: E.04.II.B.23
Global Mercury Project - Protocols for Environmental and Health Assessment i
Summary
Ai-tisanal and small-scale gold mining (ASM) is a poverty-driven activity that
provides an important source of livelihood for rural communities. As the
price of gold has been increasing, the number of artisanal gold miners has
risen to between 10 and 15 million people worldwide, producing from 500 to
800 tonnes of goldla and emitting as much as 800-1000 tonnesla of mercury
(Hg). These activities are frequently accompanied by extensive
environmental degradation and deplorable socio-economic conditions, both
during operations and long after mining activities have ceased.
One option to determine the extent of environmental and human health
effects of ASM Hg is to conduct an Environmental Assessment (EA). In
general, EA is a tool used to identifl, predict adverse effects and determine if
mitigative actions are required.
However, the methodologies used in EA for large mining projects involving
heavy metals are not ideally suited to assess the effects caused by Hg released
by ASM in developing countries. This means that environmental assessments
of ASM activities must be innovative and adapted to particular situations in
the different countries where the activities take place. This is especially true
when working with artisanal miners in impoverished and developing
countries, where remote and difficult environments with little infrastructure
and logistic support can pose many challenges.
Metallic mercury, which is the main form of Hg released by ASM, is
capricious and difficult to work with. Because of the naturally volatile state
of Hg and other confounding anthropogenic sources of Hg, this makes data
interpretation difficult. Perhaps more importantly, the transformation of
metallic Hg into its most toxic form, methylmercury (MeHg), is not clearly
understood and there are no general rules governing this transformation.
When Environmental and Health Assessments (E&HA) are conducted to
determine Hg exposure, geochemical and biological samples should be
carefully chosen to fulfil1 assessment objectives. In most cases, limitations of
resources and time result in "short cuts" that can significantly impair data
interpretation later on. Knowing that, the purpose of each monitoring step
must be defined clearly before starting any field activities. Proper design of
monitoring programs before entering the field is absolutely vital to establish
the relevance and priorities for the sampling procedures.
Since 1995, UNIDO has been providing technical assistance to the small-
scale mining sector in developing countries. Through numerous projects
dealing with the introduction of cleaner technologies and mercury pollution
abatement, the Organization has assessed the environmental and health
Global Mercury Project - Protocols for Environmental and Health Assessment ii
impacts of Hg pollution caused by artisanal gold miners, inter alia in
Venezuela, Ghana, and the Philippines. It is widely accepted that problems
associated with artisanal gold mining in different developing countries are
similar in nature. As such, solutions need a globally consistent and
effectively coordinated approach in order to deal with these complex
problems on a local level. The GMP (Global Mercury Project) was initiated
by UNIDO in August 2002 to help demonstrate ways of overcoming barriers
to the adoption of best practices, waste minimization strategies and pollution
prevention measures that limit contamination of international waters. The
Project, funded by GEF and CO-funded by UNDP and UNIDO, is
complemented by a suite of ongoing activities that are financed either
through the participating countries' resources andlor bilateral programs.
The main goals of the GMP are to:
reduce Hg pollution caused by artisanal miners on international
waters;
introduce cleaner technologies for gold extraction and teach miners
how to use these technologies;
develop capacity and regulatory mechanisms within local
governments that will enable the sector to minimize Hg pollution;
introduce environmental and health monitoring programs;
build capacity in local laboratories to assess the extent and impact of
Hg pollution.
The monitoring component of the Global Mercury Project (GMP) has
specific goals, which are described in Objective 3 of the project proposal:
"identzfi hotspots in project demonstration sites, conduct geochemical and
toxicological studies and other Jield investigations in order to assess the
extent of environmental (mercuuyl pollution in surrounding water bodies and
devise intervention measures."
One key feature of the monitoring program should be that it is designed to
follow the evolution of Hg pollution in a mining area over time. To be
successful, the program must focus on investigating bioavailability and
bioaccumulation of Hg. Biota are the ultimate indicators providing direct
evidence that Hg in the environment has become bioavailable and is being
bioaccumulated. This document highlights the relevance of sampling aquatic
biota and diminishes the importance of sampling water due to the low Hg
levels in solution. Evidence of bioaccumulation must be obtained or
predicted, in order to evaluate the appropriate course of action. If impacts to
biota were not demonstrated at a contaminated site, then containment and
long-term management would be more appropriate than other aggressive
Global Mercury Project - Protocols for Environmental and Health Assessment iii
remediation measures. This, of course, is based on the acceptability to
regulators.
As such, the monitoring program should establish simple, replicable and
sustainable operational protocols for observing how Hg levels in different
environmental and biological samples change over time. These protocols
must then be transferred to environmental agencies, mining-related
institutions and researchers to ensure that these groups apply sound
techniques for sampling, sample preservation, transportation, analysis, etc.
An important objective of the monitoring steps of the GMP is the
identification of mining hotspots, which are sites with high concentration of
metallic Hg. Often, mercury has been dumped by artisanal miners, into or
near streams. There are also sites with the potential to become
environmental hotspots; these are sites where Hg has been transformed into
a more toxic and available form (i.e. methylmercury). Hotspots can have
dimensions of a few square meters to hundreds of square meters and are the
main sources of Hg dispersion into aquatic systems. Thus, they impact
thousands of people who may or may not be involved with the mining
activities. Identification and assessment of the risks posed by these hotspots
should be a main objective of the Environmental Assessments.
Sampling procedures for such hotpots must be site-specific, taking into
consideration the characteristics of the mining activity; the biodiversity of the
region; the accessibility and availability of resources; risks; logistics; etc.
Therefore, these Protocols, designed for the GMP, do not provide many
details for such sampling. However, the Protocols do present the scientific
rationale behind the decisions on what must be preferentially sampled and the
methodologies. The researcher conducting E&HA must have a great deal of
flexibility to adapt these concepts to the field conditions and the available
budget. In EH&A, researchers must be careful not to create false expectations
among local stakeholders related to solutions regarding Hg pollution.
Environmental assessment is merely an initial step in addressing the issue by
identifying problems and proposing solutions. This is frequently not
understood by local stakeholders or by government regulators, who want to
see procedures implemented and problems solved as quickly as possible.
In terms of technical solutions, when a situation with Hg vapour exposure is
identified, such as when miners are burning amalgam in open pans, there are
a number of quick and simple solutions that can be implemented immediately
to reduce Hg exposure. These include the use of homemade retorts to recover
Hg, removing women and children from the amalgamation area and
discouraging the burning of amalgams in closed areas such as kitchens. These
simple measures can be brought to the attention of miners and other
Global Mercury Project - Protocols for Environmental and Health Assessment iV
individuals exposed to Hg easily, thus reducing the community's exposure to
Hg significantly. To limit exposure of individuals or families to MeHg, the
consumption of large amounts of carnivorous fish should be avoided.
Instead, they should consume fish with lower MeHg concentrations or dilute
their meals with vegetables, when these are available.
There is considerable controversy as to whether or not therapies should be
discussed with Hg intoxicated people during a monitoring campaign. For
ethical reasons, UNIDO has adopted the approach to inform the local and
regional health care authorities when Hg intoxication problem is detected.
UNIDO's mandate is to provide assistance in eradicating pollution sources,
not to undertake active intervention. Although the organization understands
that the health conditions of affected communities must be considered,
medical intervention should only be undertaken by physicians operating
within organizations better qualified for this task than UNIDO.
This document gathers information from many scientific publications and
from the practical experience of the authors and their colleagues. Many
"hints" provided here have been discovered through trial and error on
projects not reported in scientific journals, for a number of international
institutions. This information is offered to facilitate the implementation of the
EH&A Protocols and to assist researchers who are operating in difficult field
situations.
Global Mercury Project .Pr otocols for Environmental and Health Assessment V
Table of Contents
SUMMARY ................................................................................................................................... I
TABLE OF CONTENTS .............................................................................................................. V
LIST OF TABLES ...................................................................................................................... IX
LIST OF FIGURES ............................................................................................................... IX
ACKNOWLEDGEMENT ............................................................................................................ X
IMPORTANT NOTE .................................................................................................................. XI
PART 1 - ENVIRONMENTAL ASSESSMENT ...................................................................... 12
1. 1 . AMALGAMATION AND MERCURY RELEASES ........................................................ 17
1.1.1. Mercury Used by ASM ................................................................................................. 18
Amalgamating ................................................................................................................. 18
Cyanidation of Tailings ................................................................................................... 21
Removing Excess Hg ...................................................................................................... 23
Burning Amalgams ......................................................................................................... 23
Recycling Mercury .......................................................................................................... 28
Melting Gold ................................................................................................................... 28
The Hglost:Auprodurcaetdio ................................................................................................. 29
Other Important Aspects ................................................................................................. 34
1. 1 . 2 . Evaluating Hg Releases ................................................................................................ 37
Sampling ASM Operations ............................................................................................. 37
1.2. CHARACTERIZING CONTAMINATION AND POLLUTION ...................................... 39
1.3. SOILS AND SEDIMENTS ................................................................................................. 42
1.3.1. Determining Soil and Sediment Background ............................................................... 46
Sampling Soils and Sediments for Background Determination .....................................4 8
1.3.2. Dispersed Contamination. ............................................................................................. 52
Atmospheric Deposition Rates ....................................................................................... 56
Atmospheric Deposition Forms ...................................................................................... 59
Sampling Soils and Sediments with Dispersed Hg Contamination ............................... 60
1.3.3. Hotspots ........................................................................................................................ 62
Sampling and Locating Mining Hotspots ..................................................................... 64
Sampling Air in Hotspots ................................................................................................ 69
Sampling and Locating Environmental Hotspots ........................................................... 70
1.3.4. Mercury Mobility .......................................................................................................... 75
Predicting Hg Mobility ................................................................................................... 77
Sampling to Establish Mercury Mobility ....................................................................... 78
1.4. WATER ................................................................................................................................ 80
Sampling Water ............................................................................................................... 84
1. 5 . ASSESSING MERCURY BIOAVAILABILITY ............................................................... 85
1S .1. Using Selective Extraction to Assess Bioavailability .................................................. 85
1.5.2. Using Fish to Assess Bioavailability ............................................................................ 90
Standardizing Approach .................................................................................................. 91
Impoundment Effect ....................................................................................................... 95
Sampling Fish .................................................................................................................. 97
Preserving Fish Samples ............................................................................................... 103
Bioassays ....................................................................................................................... 104
1.5.3. Using Invertebrates to Assess Bioavailability ............................................................ 106
Sampling Aquatic Invertebrates .................................................................................... 110
Global Mercury Project .Pr otocols for Environmental and Health Assessment
1.5.4. Taxonomic Richness and Abundance to Assess Bioavailability ................................ l l l
1.5.5. Using Physico-chemical Variables to Assess Bioavailability .................................... 1 12
Humosity ........................................................................................................................ l 13
Water Conductivity ........................................................................................................ 1 13
Sediment pH .................................................................................................................. 1 13
Sediment Eh ................................................................................................................... 114
Biomass .......................................................................................................................... l 14
Temperature .................................................................................................................. 1 14
1.5.6. Using Humans to Assess Bioavailability .................................................................... 114
Urine .............................................................................................................................. 1 15
Sampling Urine .............................................................................................................. 11 7
Creatinine in Urine ......................................................................................................... 118
Proteinuria in Urine ....................................................................................................... 119
Blood .............................................................................................................................. 119
Sampling Blood ............................................................................................................. 120
Hair ................................................................................................................................ 120
Sampling Hair .......................................................................................................... 1 2 3
1.6. ANALYTICAL PROCEDURES ........................................................................................ 126
1.6.1. Water ............................................................................................................................ 126
1.6.2. Sediment ..................................................................................................................... 127
Digestion Procedures ..................................................................................................... 127
Direct Mercury Analysis .............................................................................................. 128
Measurement of total Hg using CVAAS ....................................................................... 129
Measurement of total Hg using CVAFS ....................................................................... 130
Measurement of total Hg using ICP/MS ....................................................................... 130
Analyzing MeHg in Soils and Sediments ............................................................... 131
1.6.3. Biota Tissue ................................................................................................................. 131
1.6.4. Urine, Blood and Hair ................................................................................................. 132
1.6.5. Other Analytical Procedures ....................................................................................... 133
1.7. QUALITY ASSURANCE/QUALITY CONTROL .......................................................... 134
1.7.1. Precision ...................................................................................................................... 134
1.7.2. Accuracy ..................................................................................................................... 135
1.7.3. Method Detection Limit .............................................................................................. 136
PART 2 - HEALTH ASSESSMENT ....................................................................................... 137
2.1. HEALTH EFFECTS CAUSED BY MERCURY VAPOUR ............................................ 139
Symptoms of Hg Vapour Exposure ....................................................................................... 139
Health Problems of ASM Exposure to Hg Vapour ............................................................... 141
2.2. HEALTH EFFECTS CAUSED BY METHYLMERCURY ............................................ 145
2.2.1. Iraq Tragedy ................................................................................................................. 145
2.2.2. The Minamata Outbreak .............................................................................................. 146
2.2.3. MeHg Poisoning .......................................................................................................... 147
Effects of MeHg on the Brain ........................................................................................ 147
Main Symptoms ............................................................................................................. 147
Congenital Effects of MeHg .......................................................................................... 149
2.2.4. Low-level MeHg Exposure ......................................................................................... 150
2.3. GUIDELINES AND REFERENCE DOSES .................................................................... 153
2.3.1. Hg in Urine .................................................................................................................. 153
2.3.2. Hg in Fish .................................................................................................................... 153
2.3.2. Hg inHair .................................................................................................................... 154
2.4. SAMPLING FISH FOR HEALTH ASSESSMENT .......................................................... 155
Global Mercury Project Protocols for Environmental and Health Assessment vii
.
2.5. MEDICAL EXAM ............................................................................................................. 157
2.5.1. Procedures ................................................................................................................... 157
2.5.2. Confounding Factors ................................................................................................... 162
2.5.3. Data Management ....................................................................................................... 163
2.6. PUBLIC INFORMATION ................................................................................................ 169
2.7. A SUGGESTED SEQUENCE OF ACTIONS .................................................................. 170
2.8. DISCLAIMER ................................................................................................................... 171
REFERENCES .......................................................................................................................... 172
APPENDIX 1: EXAMPLE OF A HEALTH ASSESSMENT SURVEY. ............................... 209
1. General Questionnaire ...................................................................................................... 210
2 . Health Questionnaire ........................................................................................................ 216
3 . Clinical-Neurological Examination .................................................................................. 221
4 . Specific (Neuropsychological) Tests ................................................................................ 226
5 . Specimens ......................................................................................................................... 236
6 . Laboratory Analysis Results ............................................................................................. 237
7 . Medical Score Sum ........................................................................................................... 238
8. Decision for the diagnosis of "chronic Hg intoxication" ................................................. 240
APPENDIX 2: EXAMPLE OF A SOCIO-ECONOMIC QUESTIONNAIRE ....................... 242
APPENDIX 3: USER'S GUIDE. .............................................................................................. 251
Introduction ........................................................................................................................... 251
What does one have to do before starting an E&HA? ......................................................... 251
How does one assess mercury releases from ASM? ............................................................ 252
Is it possible to estimate Hg releases from ASM based on soillsediment analyses? ........... 253
How can the Hg:Au ratio be used to estimate Hg emissions? ........................................ 253
Is it possible to analyze the levels of Hg in air? ................................................................... 253
How can one determine if the Hg pollution source is dispersed or concentrated? .............. 254
What are the main pathways of Hg to humans? ..................................................................2. 54
What is the difference between Hg contamination and pollution? ...................................... 255
How is pollution characterized? ........................................................................................... 255
What is a mining hotspot? .................................................................................................... 255
What is an environmental hotspot?. ...................................................................................... 255
How does methylation of metallic Hg occur? ...................................................................... 255
How does one determine if Hg dispersed over large areas is bioavailable? ........................ 256
What are the most favorable environments to produce methylmercury? ............................ 256
What information is obtained when one analyzes Hg in soilslsediments? .......................... 256
What is the best way to establish reference Hg levels in soillsediment? ............................. 257
How does one characterize and locate Hg mining hotspots? ............................................... 260
Can Hg from mining hotspots be dispersed (mobilized) in solution? .................................. 262
How does one characterize and locate an environmental hotspot? ...................................... 262
Is it important to analyze soillsediment around mining impacted areas? ............................ 263
How does one determine if Hg from hotspots is being dispersed? ...................................... 263
How can it be determined if mining hotspots are also environmental hotspots? ................. 265
When should a mining hotspot be mitigated? ...................................................................... 265
What is the purpose of analyzing Hg in fish? ....................................................................... 266
Is it possible to determine if Hg bioavailability is increasinglreducing over time? ............. 266
What is the most appropriate fish species to be chosen as bioindicator?. ............................ 268
If the ideal bioindicator is not edible, is it still useful to be sampled? ................................. 269
What is the procedure to sample fish for Hg analysis? ........................................................ 269
Is there another method to characterize Hg bioavailability? ................................................ 270
Is it possible to sample other animals instead of fish to characterize Hg bioavailability? .. 271