Mercury in Chile

Rev Environ Contam Toxicol 183: 1-19 Springer-Verlag 2004

Mercury Contamination in Chile: A Chronicle of a Problem Foretold

Carlos A. Barrios-Guerra

Contents

1. Introduction A. Historical Use of Mercury in Chile .............................................................. . B. Geography and Sources of Mercury in Chile ................................................ 2 C. Present Conditions ... ... ... .... ........ ..... ...... .... .... ... ....... ... ... ........ ... ... ........ ...... ...... 4

II. Environmental Contamination ............................................................................. 6 A. Plants. Animals, Soil, and Bays ..................................................................... 6 B. Rivers .............................................................................................................. 9

III. Human Contamination .. ... ...... ...... ... ..... .... ... ... ....... ...... ...... .... ........ ..... ...... ... ......... 11 A. Occupational Exposure ................................................................................... I I B. General Population Exposure ......................................................................... I I C. The Case of a Small Mining Industry and Independent Mining .................. 13

IV. Government Limits for Mercury Contamination ................................................ 14 V. Conclusions .......................................................................................................... 15

Summary .................................................................................................................... 16 References ...... ... ................. ... .... ... ........ ......... ...... ... ....... .................. ... ... ...... ........... .... 17

1. Introduction A. Historical Use of Mercury in Chile

The Incas and the people they dominated, some of which lived in the northern central region of Chile, used mercury for a long time without understanding much about it. At first, its usage was only as an adornment on objects utilized in their sacred ceremonies. The mercury was found along with other metals in a rock that was known as Llimpi (Quechua = color, paint). After the arrival of the Spaniards to America, between the years 1566 and 1567, a Portuguese rec-ognized that the rock called Llimpi was the same as a rock from Castilla (Spain) known as "bermel/un." This finding led to the search and eventual discovery of mercury mines. The mercury extracted from these mines in Chile was distrib-uted all over the Spanish empire as far north as Mexico to obtain gold and silver. Even the residues from old mines were reused to acquire additional gold and silver.

In this process, the mineral was ground and then sifted into boxes where

Communicated by Lilia Albert.

C.A. Barrios-Guerra Laboratorio de Toxicologfa. Facultad de Farmacia. Universidad de Concepci6n (Chile), Casilla 237, Barrio Universitario, Concepci6n, Chile.

2 C.A. Barrios-Guerra

saturated salt water was added to extract the mud. The amalgamated metal was placed into tubs containing water where the mud was further extracted using presses that precipitated the amalgam. This mixture of mercury and metal was then put into a cloth and squeezed under pressure, resulting in a residue (pella) with only one sixth part being pure metal and the other being mercury. To separate the metal, the residue was put into clay jars and covered with charcoal, which was ignited to produce the necessary amount of heat. Under this condi-tion, the mercury evaporated and then condensed as it came in contact with the walls of the jar. This condensation was then distilled resulting in a pure metal of the same form and size only five parts less in weight than the original. As the Scriptures say, Secut argentums probatum terrae, purgatum septulum (to remove silver from the earth and mud where it resides, it must be purged and purified seven times). What was never recorded during this time was how many people became ill or died as a result of extracting gold and silver by amalgam-ation of mercury in South America.

According to Encina and Castedo (1956), the exploitation of gold and silver has developed industrially in Chile since the 17th and 18th Centuries in gold panning areas from Tiltil and Peldehue (Metropolitan Region, M.R.), Limache (Marga-Marga), Petorca, La Ligua, Vallenar (Agua Amarga), Illapel, La Serena (Arqueros), and Copiapo (Regions V, IV, and III), Alhue, Rancagua (Region VI) and Magallanes (Region XII). By the end of the 18th Century, 253 mines and permanent panning areas were in existence where gold and silver extraction was being accomplished with the use of mercury. In 1832, Juan Godoy, a miner, discovered the silver mine of Chafiarcillo in the south of Copiapo, and soon afterward other miners discovered the Three Point mine and free and fixed streams of silver. However, when the metal was exhausted, mercury extraction was incorporated to remove the remaining silver. The amount of mercury re-leased into the environment as a result of this exploitation is unknown. How-ever, it is estimated that 21,000 kg pure silver was produced in Chafiarcillo alone during its peak production period.

B. Geography and Sources of Mercury in Chile Chile is geographically located in the extreme southwest of South America, between the Pacific Ocean and the Andes Mountains (parallel 17 30' and 90 00' S latitude), with a meridian axis of 70 W. Chile occupies an area of 756,626 km2, the length of which is 4,270 km, from the border with Peru to Cape Hom, and a width of 200 km (90-445 km), with 80% of the country being mountain-ous (Fig. 1). Its landscape varies from desert areas in the north to valleys, moun-tains, and polar zones in the south. The short distance between the Andes Moun-tains and the seacoast prevents good development of the rivers. Chile is a country with a high amount of seismic activity and several active volcanoes. It has a population of 15 million with an annual demographic growth rate of 1.15%. Thirty-nine percent of the people are younger than 20 years of age and the life expectancy is 75.4 years. Illiteracy afflicts 4.8% of the total population, and the degree of urbanization is 85%.

..

South Pacific Ocean

Isla San Ambrosio

Isla San Felix

o I o

Easter Island and Isla Sala y Gomez are nol shown.

200 400 km , , I

200

Mercury in Chile

B 0 L I V I

NT I N A

Ocean

,

400 ml

Fig. I. Geographic location of Chile in South America.

3


Large industrial growth within the past 50 years, especially in the areas of mining, forestry, and production of cellulose and paper, has increased the level of environmental contamination in the more industrialized zones of the country, which have a higher population density. Two situations arise from this: (1) an uncontaminated ocean 100 miles off the coast, and (2) a greatly contaminated coastline due to human activity. The majority of the large cities and industrial centers are no farther than 90 km from the coast, which results in 75% of their wastes being eliminated into the ocean, specifically between the Aconcagua and BioBio Rivers (Regions V and VIII) (Fig. 2). Despite the fact that the Chilean coast possesses many beneficial conditions, such as open areas, low tempera-tures, circulation of large currents, and a narrow continental plate that helps in absorbing and decreasing the concentration of chemical substances, there exist specific areas with extremely high levels of pollution (Barrios 1979; Gutierrez 1991; Arcos et al. 1992).

Existing information shows that in the Chilean coastal zone, from Regions I and II, the main sources of contamination are heavy metals and industrial resi-dues coming from the mining industry or from storage in territorial zones with the subsequent contamination of rivers and streams. This situation is aggravated by the climatic phenomenon known as "Bolivian winter," which brings heavy rains during the summer months that cause flooding and subsequent spillover of large amounts of deposited minerals, along with overflowing of wastes aban-doned by mining companies in the area.

Due to the high population and industrial density found from Regions IV to VIII, there is a significant concentration of heavy metals, as well as sewage and untreated industrial liquid residues, in the rivers and other water sources. The area presenting the highest levels of industrial and domestic contamination, re-sulting from forestry debris and cellulose (Chuecas 1989; Barrios 1994), is the coastal zone from the Aconcagua and Maipo rivers (Region V, M.R.) to the BioBio river and the Bays of Concepcion, San Vicente, Coronel, and the Gulf of Arauco (Region VIII). The Chilean Oceanographic Administration has re-ported that this is the most contaminated area of the country. The zones least contaminated by metals are located from Regions IX to XII, as well as Antarc-tica, due to the large expanse of virgin soil and strict controls maintained on the activities involved to avoid future deterioration of the environment in this area (Chiang 1992).

C. Present Conditions

For many centuries, the problem of contamination was never seen in its true perspective because the objective was to demonstrate the efficiency of mercury in different industrial processes. Nowhere else was this more apparent than in developing countries where it was necessary to exploit the natural resources to elevate the quality of life. The principal concern of their governments was to explore and exploit new sources of minerals. The increase in exploitation of raw materials in Latin American countries has had, as a consequence, the elimination

Mercury in Chile

"

III

IV

V l """-R.M J. ~--1

VIIV~ VIII tI. I

IX -..= I

Tarapaca

Antofagasta

Atacama

Coquimbo

Valparaiso Region Metropolitana Liberlador General Bernardo O'Higgins Maule

Biobefo

Araucanfa

Los Lagos

Aisen del General Carlos Ibanez del Campo

Magallanes y Anlarlica Chilena

Fig. 2. Regional map of Chile.

5

6 c.A. Barrios-Guerra

of large amounts of mercury, resulting in contamination problems in the air, ground, and water (Barrios 1985, 1994; Martinelli et al. 1988; MaIm et al. 1990; Branches et al. 1993). For years, Latin America has viewed the environment, especially the oceans, as one large garbage dump that is capable of processing anything that goes into it. For that reason, the coastal zones have been laden with chemical wastes, minerals, and industrial liquids with the passing of the years. Worst of all, humankind seems to be unconscious of the fact that not only are they destroying the plants and animals, both on land and in water, but that these toxic substances are returned through the air, water, and food, which subsequently endangers their own health.

II. Environmental Contamination A. Plants, Animals, Soil, and Bays

The first work carried out on the environment in relation to mercury (Hoffmann 1978) was done in the Lenga Estuary (33 44' S; 73 9' W), located in Region VIII. This estuary and its surrounding waters in the San Vicente Bay (11.5 km2; 36 44' S, 73 09' W; Fig. 3) represent a very important ecosystem for the breed-ing of different fish species, as well as providing a seasonal resting area for breeding of local and other aquatic birds from the northern hemisphere. Hoff-man's results showed that the concentration of total mercury in the water of Lenga Estuary ranged from 6.0 to 140.1 J..lgIL, whereas from San Vicente Bay the values were 0.8-5.8 J..lgIL. In plankton from San Vicente Bay, the concentra-tion of total mercury ranged from 0.213 to 4.70 J..lg/g, with mercury concentra-tions in sediment ranging from 0.042 to 167.6 J..lg/g WW (0.045-265.6 J..lg/g DW).

In Gracilaria chilensis algae found in the Lenga Estuary, the mercury con-centration was 1.627 ppm WW, whereas Iridaea laminarioides had a concen-tration of 0.344 ppm WW. San Vicente Bay, on the other hand, showed a G. chilensis average mercury concentration of 0.048 ppm (38.22 J..lg/g WW). The mercury concentration measured in the Cyperaceae plant Scirpus sp., which grows along the edge of this body of water, ranged from 0.045 to 265.6 J..lg/g DW (0.04-38.22 J..lg/g WW).

Mercury concentrations found in Aulacomya alter (a mussel) from Concep-cion Bay (160 km2; 36 40 S, 73 02 W), San Vicente Bay, and the Gulf of Arauco (492.5 km2; 36 48 S, 73 10 W), were 0.19, 0.14, and 0.24 mg/g DW, respectively. Concholepas concholepas (abalone), however, showed mercury concentrations ranging from 0.003 to 0.780 J..lg/g DW. These results show that mercury concentrations increase the higher one moves up in the food chain.

A study carried out by the University of Concepcion for the Regional Secre-tariat for the Ministry of Planning in Region VIII (SERPLAC 1980) found mer-cury concentrations in marine sediment at 0.15 ppm from Concepcion Bay, 0.38 ppm from San Vicente Bay, 0.25 ppm from the Gulf of Arauco, and 72.9 ppm from Lenga Estuary. Water samples taken from Concepcion Bay, San Vicente Bay, and the Gulf of Arauco had mercury concentrations of 1.50, 0.31, and 0.31

74.00

N~ 36.30

Bahia San Vicente

37.00 Isla Santa Maria~

Punta de Lavapie

37.30

38.00

o () u: C3 il: o z ..: w u o

Isla l;jMOCha

38.30

Mercury in Chile

73.00 72.00

o 20 40 km.

-Fig. 3. Sketch of Biobio (Region VIII) the first industrial region of Chile.

7

/lg/L, respectively; normal levels are from 0.05 to 0.19 /lg/L. Two investigations by Salamanca et al. (1986, 1988) from Concepcion Bay, San Vicente Bay, and the Gulf of Arauco reported mercury concentrations in surface sediment of 0.16 0.08, 0.38 0.05, and 0.25 0.15 ppm DW, respectively.

Another study by Diaz (1992) in Region VIII determined that the concentra-tion of metals, one of which was mercury, in Tagelus dombeiii (clams, sea aspara-gus) was representative of the marine life on the seashore from the area under


study and, therefore, a good indicator of water quality. Concentrations of total mercury and methyl mercury were measured in ocean water, suspended solids, sediments, industrial effluent, and in the liver from clams in samples taken at four seasonal periods during the year. A similar zone from Nercon (Region X) having little human influence was chosen as a control population. The results revealed significant differences in total mercury and methyl mercury concentra-tions, not only between sample locations but also between seasonal periods. In liquid and suspended solid samples, for example, the highest average concentra-tion corresponded to the sampling site of industrial effluent (3.75 JlglL, n = 8 in liquid; 44.58 Jlglg in solids). The highest concentration for methyl mercury corresponded to the liver of T. dombeii (0.87 Jlg [CH3Hglg] DW). The results showed that the concentrations of total mercury and methyl mercury were less in the control zone than in the zone under study, with the exception of total mercury concentration in sediment from San Vicente Bay, because the quality of water from this area does not meet international standards. Concerning human health risks, the concentration of total mercury and methyl mercury found in the liver organ from T. dombeii (1.96 1.42 JlgHg/g and 0.81 0.43 Jlg CH3Hg/ g) exceeded the recommended standard set by the U.S. Food and Drug Adminis-tration (1 Jlg/g) and the guidelines of the World Health Organization (200 Jlg CH3Hg/personlwk).

In a study carried out by Encina (1993), metal concentrations were measured in water from San Vicente Bay, Coliumo, and Quidico (Region VIII). The re-sults demonstrated that San Vicente Bay had the highest mercury concentration in its water (X = 0.26 Jlg/L, SD = 0.16) as compared to Coliumo (X = 0.17 Jlg/ L, SD = 0.06) and Quidico (X = 0.12 SD = 0.03 JlglL), these last two bays being located far from the centers of industrial water effluents. This same study also measured mercury concentration in algae that are important for the economy and ecology: G. chilensis, l. laminarioides, and Iriadaea ciliata (Table 1). With the exception of G. chilensis in Quidico, none of the samples exceeded the recommended standard for Chile (1 Jlg/g]); however, they did exceed those used by the European Economic Community and the United States (0.1 Jlg/g).

Because exportation of marine products has important economic implications for Chile, the majority of mercury research has been carried out in fish to quan-tify contamination levels and evaluate human health risks related to seafood

Table 1. Mercury levels (ppm) in algae versus location.

San Vicente Coliumo Quidico

Alga X SD X SD X SD

Gracilaria chilensis 0.l8 0.23 0.05 0.06 n.d. n.d. Iridaea ciliata 0.14 0.11 0.06 0.04 0.07 0.04 Iridaea laminarioides 0.21 0.07 0.09 0.07 0.04 0.04

n.d.: not detected.

Mercury in Chile 9

consumption (Chiang and Nunez 1983; Bore et al. 1987, 1988; Chiang 1988; Diaz et al. 1989; Chuecas et al. 1991; Gonzalez 1994). A summary of these studies is presented in Table 2.

Another study by Gonzalez (1994) investigated heavy metals in the trophic food chain: organic material found in sediment (particulate material), red shrimp (Pleuroncodes monodon), and black cusk-eel (Genypterus maculatus) from the Gulf of Arauco. The concentration of mercury found in sediment was 0.39 ppm, which was less than that found in neighboring Coronel Bay, 0.46 ppm. Particu-late material in suspension at the bottom of the Gulf of Arauco revealed a mer-cury concentration of 10 ppb whereas on the surface the concentration increased to 37 ppb, indicating that the source of mercury was principally discharges from the BioBio River. Mercury concentration in red shrimp was 0.31 0.29 ppm, which was similar to that found in muscle tissue from black cusk-eel (0.33 0.26 ppm), with 86% of the mercury present in the sediment being found in both species. Black cusk-eel possessed 110% of the mercury found in its princi-pal source of food, red shrimp, which, in turn feeds off the organic material contained in marine sediment. all of which is reflected in these mercury concen-tration factors: black cusk-eel/shrimp, 1.01 and black cusk-eel/sediment, 0.94.

In the city of Antofagasta (Region 11). another region with high contamination levels, an environmental study carried out by a consulting company (Dames & Moore) between the years 1993 and 1996 reported the following mercury con-centrations in marine sediment from the seashore of Antofagasta: 1993, 8.6 ppm; 1994, 20.0-23.8 ppm; 1995. 19.5-25.4 ppm; and 1996, 20.5-28.4 ppm. The high concentrations found in these sediments during this time was attributed to wastes from an old gold refinery located in the northern section of the city that stopped operating in the year 1970.

B. Rivers

Investigations in rivers and effluents from the central zone of the country (Re-gions V, VI, and M.R.) in 1989 found mercury concentrations of 2.2 /-lg/L, much higher than those allowed by national and international standards, in one of the canals (Zanjon de la Aguada) in Santiago city (Villalobos 1989; Salas 1991). This contamination resulted from domestic and industrial residues from the southern section of the city and posed a health risk to the popUlation because these waters were used for irrigating nearby crops used for human food. The mercury concen-tration from the principal river that crosses the city of Santiago (Mapocho), on the other hand, was

......

o

Tabl

e 2.

Mer

cury

co

ncen

trat

ions

(/.1g!

g mu

scle

tiss

ue) i

n fis

h, C

hile

(198

3-199

9).

Spec

ies

Hg

(/.1g!g

) Sa

mpl

e R

egio

n/pl

ace

Dat

e A

utho

rs

Yea

r

Sard

inop

s sa

gax

0.06

20

I/Iqu

ique

19

86

Bor

e et

aI.

1988

Sa

rdin

ops

saga

x 0.1

3 20

IU

CaId

era

1986

B

ore

et

aI.

1988

n

Engr

aulis

rin

gens

0.4

8 20

IU

CaId

era

1991

C

huec

as e

t aI

. 19

91

?> Sa

rdin

ops

saga

x 0.1

3 20

IV

/Coq

uim

bo

1983

B

ore

et

aI.

1987

t:x

l M

erlu

cciu

s ga

yi

0.02

10

V IV

alpa

rais

o 18

83

Chi

ang

an

d N

unez

19

83

3. Tr

achu

rus

mu

rphy

i 0.0

96

10

V IV

alpa

rais

o 19

83

Chi

ang

an

d N

unez

19

83

0 '" 6

Mer

lucc

ius

gayi

0.0

02

n.r

. V

IV al

para

iso

1988

C

hian

g 19

88

$::=

Trac

huru

s m

urp

hyi

0.017

V

IV aI

para

iso

1988

C

hian

g 19

88

0 n.r

. =

t ~ Tr

achu

rus

mu

rphy

i 0.0

47

n.r

. V

IV aI

para

iso

1991

C

huec

as e

t aI

. 19

91

Mer

lucc

ius

gayi

0.0

4 n.r

. V

IV aI

para

iso

1991

C

huec

as e

t al

. 19

91

Gen

ypte

rus

ma

cu

latu

s 0.3

4 n.r

. V

III/C

once

pcio

n 19

93

Gon

zale

z 19

94

n.r

.: not r

epor

ted; S

ardi

nops

saga

x: C

hilea

n sa

rdin

e, Pa

cific

sard

ine;

Engr

aulis

rin

gens

: an

chov

y; M

erlu

cciu

s ga

yi: C

hil-

ean h

ake,

Pacif

ic ha

ke; T

rach

urus

murp

hyi:

jack m

acke

rel;

Gen

ypter

us m

acu

latu

s (II

): bl

ack

cusk

-eel.

Mercury in Chile 11

at 1.0-7.0 J.lg/L and those for drinking water at 0.1-0.2 J.lg/L (SanIes 1983, 1984; Sanies et al. 1987).

III. Human Contamination A. Occupational Exposure

A study by Maureira (1977) in an occupational group exposed to mercury va-pors in a chi oro-soda factory located in the Region VIII revealed mercury con-centrations of 0.010-0.225 ppm in urine samples taken from workers, levels below the Chilean standard of 0.30 ppm. These concentrations correspond to an average environmental air value of 0.005 mg/mJ, with an SD of 0.001-0.026 mg/m3 and a maximum environmental air concentration of 0.040 mg/m3 A follow-up study (1978-1998) on environmental concentrations of mercury vapor in electrolytic cells of this factory showed a maximum average value of 0.046 mgl m) with an SD of 0.0012-0.1 10 and a minimum average value of 0.007 mg/m3 with an SD of 0.001-0.02.

In addition, there exist many sources of contamination in Chilean workplaces that have not been studied, such as dental offices and hospitals, not to mention the massive use of batteries in domestic appliances and toys that are thrown away directly into the domestic trash.

B. General Population Exposure

The first investigations that studied the general population exposure to mercury were done in the years 1976 and 1982 in Region VIII and involved the compari-son of people living in fishing villages and their relation to mercury (Nunez et al. 1976; Barrios et al. 1982). One of these studies showed that exposure to mercury came about as a result of diet only (Tumbes), while the other (Lenga) demonstrated that the exposure was through diet and industrial contamination by the cloro-soda factory (see Fig. 3). The results from a total of 280 permanent residents from these villages showed an average of 19 ppb in those living in Tumbes and 71.02 ppb in those from Lenga, the latter demonstrating the inci-dence of industrial contamination. In the Lenga fishing village, an analysis done on the variation of mercury concentration according to age revealed an increase in mercury values until 30 yr of age, with a subsequent decrease and stabiliza-tion of these values between 34 and 40 yr (in ppb), without any significant difference between sexes. Milk samples taken from 5 women living in Lenga who were breastfeeding their children during the study showed an average mer-cury concentration of 4.9 ppb (SD = 1.8-16.2).

The objective of a study done between 1986 and 1988 (Interamerican Group for Research Environmental Epidemiology 1990) was to generate a hypothesis concerning the possible relationship between mercury, lead, and arsenic concen-trations and human health in communities living alongside rivers from seven Latin American countries. In Chile, the BioBio River and three riverside com-munities were chosen for study based on previous contamination background


and selected according to supposed risk, defined as high risk (Nadir, N), me-dium risk (I), and low risk (Zenith, Z), to compare exposure levels with descrip-tive and qualitative variables such as social status, geography, age, diet, and water usage. Mercury concentrations reported in these communities are shown in Table 3. Although this study concluded that the levels of metals found do not constitute a public hazard, the results highlight the importance of safeguarding potentially exposed communities that are localized on the edges of these rivers.

Other investigations by Diaz et al. (1989) and Martini et al. (1993) in heavy metals reported mercury as a food contaminant, especially in seafood products such as canned jack-mackerel (Trachurus murphyi), oil, and fish meal from Regions I, V, VIII, and the Metropolitan Region (M.R.). The results showed that mercury was the element present in the highest concentration in oil and fish meal from the Regions I, V, and VIII (0.71, 0.39, and 0.73 mg/kg, respectively). The concentration measured in canned jack-mackerel from food markets in the Metropolitan Region was 0.62 mg/kg, a value less than the highest acceptable limit (1.0 mg/kg) according to the food and health guidelines set by the Chilean Health Ministry (in 2000), but higher than the European Community and U.S. standards. A study carried out between 1991 and 1997 in pregnant women (PW) and nursing women (NW) residing in selected fishing villages along the coastal zone of Region VIII in Chile assessed the extent of environmental exposure to mercury through the diet of a population group having higher fish and seafood consumption (Bruhn et al. 1994a,b, 1995, 1997). The control group was an equiva-lent group with negligible fish and seafood consumption. The samples were scalp hair collected from the occipital head region and venous blood. Total mercury [Hg-T] reported by the first study (1991-1993) in scalp hair for the coastal group was: n = 153; X = 1.79; SD = 1.50; range = 0.14-9.72 and that for the control group n = 26; X = 0.42; SD = 0.15; range = 0.20-0.79. The arithmetic mean for the coastal group was significantly higher than the mean for the control group. These mercury levels determined in the hair are considered normal for a population with dietary habits based mainly on seafood products.

The second study (1994b) was done in a high-risk group of newly PW (aged

Table 3. Distribution (%) of total mercury level in blood (J..lg/L).

Adults Children Total

Community Z N Z N n 163 175 165 102 101 lOS SI4

30.0 0.0 0.6 0.0 2.9 0.0 0.0 0.5

Z: Zenith (low risk); I: (medium risk); N: Nadir (high risk).

Mercury in Chile 13

17-40 yr) not occupationally exposed to mercury but living in five fishing vil-lages located within the more-polluted area of the coastal zone and consuming at least one fish meal per week. The control group was made up of nine newly PW (aged 14-35 yr) residing in a town located inland in the same region far from the coastal area, with a negligible fish or seafood consumption. The fishing village represented the largest differences in Hg-T content with respect to the control group studied in 1991-1993.

The arithmetic mean of Hg-T results in scalp hair from the coastal group (2.44 l.30 mg/kg) was significantly higher than the mean obtained for the control group (0.40 0.l6 mg/kg), being almost 35% higher than the mean ob-tained in the coastal group during the 1991-1993 period, but 20% lower than the pooled mean (3/06 l.97 mg/kg; n = 46) obtained in that period for the same five fishing villages. The arithmetic mean of Hg-T in blood from the coastal group (9.04 5.05 /-lg/kg) was also significantly higher than the mean of the control group (2.73 l.27 /-lg/kg). One of the conclusions from these studies was that the concentration obtained for Hg-T and Me-Hg in the scalp hair from PW, and for Hg-T in the blood of PW, do not suggest that the selected "high-risk group" is truly at a high risk of adverse health effects due to Hg because the concentrations are within normal levels found in a population with fish consumption ranging from once a month to once a week. However, the appearance of subclinical effects in the fetuses due to low dose dietary exposure of the mother to Hg and Me-Hg should not be disregarded.

C. The Case of a Small Mining Industry and Independent Mining

The small mining industry and especially independent mining in Chile still con-tinue to exploit gold utilizing the same processes as in Colonial times (flotation, lixiviation, amalgamation) because this is an inexpensive way to obtain gold.

In a study by Vasters (2001) (ECOMIN, ENAMI, Copiapo) to assess envi-ronmental effects of the metal mining industry in Region II, two principal prob-lems concerning the potential high risk for public safety and heath and four problems regarding general risks for the environment were established. The first problem concerns the construction, operation, and abandonment of dams after the extraction and purification process and gravel deposits related to the more than 90 unused plants and approximately 50 active plants with one or more dams or gravel deposits. The deposit residues come principally from flotation, lixivia-tion, and amalgamation processes. Frequently, the design, construction, and op-eration, as well as the planning of leftover deposits, do not guarantee the physi-cal and chemical stability required to rule out long-term public health and environmental risks. Leftover spills close to dams, crumbling walls, and ground filtration were found in this region where the desert climate and the erosion of dry dam surfaces due to wind contribute to these spills. Mercury contamination from the amalgamation process in small gold mining is a serious problem in Region II, IV, and V areas with the highest concentration of small size and independent mining.


Mercury measurements taken in agriculture soil and dams in the Copiapo Valley (Region IV) showed that delta zones had the highest concentrations of mercury. This contamination of soil and dams poses a direct health danger to nearby popula-tions because mercury is continuously evaporating at normal temperatures.

The total mercury loss in amalgamation by plate, which is often accompanied by a combination of ground amalgamation in the bowl of trapiche, reaches between 200 to 800 glHg/d. The annual mercury consumption from small min-ing operations alone in the Copiapo zone (Region III) is estimated at more than 2 tons of metal mercury. Today, there exist 20 plants in Region III that use mercury on a regular basis, or sporadically in the recovery of unrefined gold, where a large part of the mercury is lost in the dams during the amalgamation, flotation, or accumulation stage.

In the year 2000, mercury concentrations in gold concentrates bought by ENAMI (National Mining Company) mills were found to be as high as 7.400 ppm. The average in concentrates for the same year was 772 ppm of mercury and 64 ppm of gold. The maximum value allowed of impurities for mercury concentrates is 500 ppm according to the Chilean standard. Small mining con-tributes with 1.1 tons of mercury to the total emission of mercury from the Paipote mill. The maximum mercury concentration in the flotation dams from flotation-amalgamation plants was 100 ppm. In liquid residues resulting from dam drainage, which is frequently used to irrigate crops, the concentration of mercury was 0.037 mg/L, which exceeds by 37 times the Chilean standard No 1.333. Mercury found in the concentrates is released into the environment from chimneys during the melting process, part of which precipitates in the dust fil-ters used during this process. The heating of amalgam (pella) to separate gold from mercury is done, in many cases, in the open air, which allows mercury to escape directly into the atmosphere. Analysis of environmental concentrations during the processes of dehydration and separation of mercury with fire found atmospheric concentrations of mercury at 320-400 )..lg/m3; the limit allowed by Chilean standards for organic mercury is 0.04 mg/m3. In factory workers from amalgamation plants, mercury concentrations measured in urine samples were as high as 1300 )..lg/L, the normal limit allowed by Chilean standards for biological tolerance of inorganic mercury in urine is 50 )..lg/L.

Another source of mercury contamination comes from the process of separat-ing the amalgam with nitric acid. There are 10 plants of this type situated in residential areas located in the community of Copiapo. Mercury left in the acidic solution damages sewage treatment plants, and it is estimated that 300-400 kg mercury is eliminated into the environment as a result of this damage, putting the urban zones of this region at high risk.

IV. Government Limits for Mercury Contamination

In Chile, the Supreme Decree No. 745 (daily law registry 08.06.93) established an Allowable Limit and a Biological Tolerance Limit for mercury concentra-

Mercury in Chile 15

tions in work places at 0.04 mg Hg/m3 and 50 mg/L in urine, and for methyl mercury 0.008 mg Hg/m3 in vapors and 10 mg/L in blood.

The Chilean Sanitary Health Guidelines (for 2000) and their official modifi-cations, Supreme Decree 897112.1999, 824124.11/1999, 475/12.07.1999 from the Chilean Health Department in Title IV "pertaining to contaminants," para-graph 1, "Pertaining to heavy metals" in Article 160 states: 'The following ele-ments cannot exceed, in the given food, the maximum limits expressed in mg/ kg of final product": in the case of mercury these are: cereals and legumes == 0.05; canned fish and shellfish == 1.00; fresh fish, refrigerated and frozen: small size == 0.50; large size (shark and tuna) == 1.50; fresh shellfish == 0.50. Chilean Standard No. 1333, concerning requisites for water quality, establishes that the maximum allowed concentration of mercury in water should not exceed 1 ).lglL. No values exist for mercury in sediment.

V. Conclusions

Analysis of the present situation of mercury contamination in Chile leads one to conclude that this problem has worsened over the years. The principal prob-lem of mercury use and contamination is the inappropriate use of small and independent mining operations, which still employ the same processes of gold and silver exploitation as in the 16th Century. Therefore, a change of mentality is needed concerning the environment by means of educational programs geared toward this population segment, as well as implementation of environmentally friendly technologies at an affordable cost.

In addition, there has been an increase in mercury use by industry and society (toys and battery-operated artifacts) that follows an inverse pattern in developing countries to that in developed countries. Only in the last few decades has man begun to realize that what is discarded into the environment returns in a more toxic form in food and water, and especially seafood as in the case of mercury, by the process of biotransformation through the food chain.

The major source of mercury contamination in Chile is the water. In this medium, mercury is recycled and can pass efficiently from one biological com-partment to another. This bioavailability increases the accumulation of mercury through all the levels of the food chain up through humans. This finding is what is revealed by the results from studies done up until now in Chile that show critical areas of mercury contamination in Regions J, II, III, IV, V, and VIII and the Metropolitan Region. It is important to note that the most industrialized region of the country, Region VIII, displayed mercury concentrations in the soil, river, bays (water, sediment, and material in suspension), and seafood (fish, shellfish, algae, etc.) higher than those accepted by the international community.

Chile needs to adopt measures to detect mercury contamination in popula-tions at risk. Furthermore, strict controls need to be incorporated to eliminate the origin of mercury release, something that has only been partially accom-plished within the last few years. This type of program requires awareness edu-


cation for the inhabitants along with appropriate legislative action, measures that should be applied to all contaminants that threaten the ecosystem and hu-man life.

Summary

This review analyzes the effects of environmental mercury contamination in Chile. This contamination generates one of the most important environmental conflicts in the country in that it affects air, ground, and water (rivers and oceans), which are fundamental in maintaining natural biotic equilibrium and at the same time important for the nation's economy.

Chile possesses extraordinarily wealthy mining resources between Regions I and IV that have developed into an extraction industry essential for the economy of the country. However, waste discharges from this production have created an environmental problem in that the majority of the mines are located in the Andes mountain range, or areas close by, and the water used in the extraction process is deposited into the rivers, significantly increasing the amount of chemical con-tamination. Therefore, the cities and downstream waters used in agriculture suf-fer the negative consequences of a natural resource that is becoming more and more scarce. In addition, minerals released from mills into the atmosphere are deposited onto the soil, drastically affecting the biological resources of these areas. One of these affected areas is the Metropolitan region, where one of the highest contamination levels of mercury in the country was found in one of its affluents due to industrial and domestic waste discharge. In a country that is only 200 Ian in width, the gathering of all these contaminants in the rivers results in a rapid flow to the ocean, thereby contaminating coastal waters and the biota. In general, this contamination has been detected in semiclosed bodies of water (bays).

Between Regions VII and IX, the principal sources of mercury contamination are related to cellulose industrial sites (Regions VII and VIII) and, until the 1980s, the bleach-soda industry. The most important industrial and fishing activ-ity is also found in this area. In San Vicente Bay, waste discharges released into the ocean include sewage, industrial residues, residues from fishing and mining industries, hydrocarbons, petrochemical derivatives, oils, and detergents. This combination of chemical assault makes the San Vicente Bay the most contami-nated in the country and the area where the majority of mercury contamination studies have been carried out. Between Regions X and XII, mercury contamina-tion is reduced due to decreased release of domestic residues, especially batter-ies and sanitary waste.

Beginning with the decade of the 1990s, Chile made a great effort to decrease contamination through governmental organizations (CONAMA, SERNAGEOMIN, DGA, ECOMIN, SONAMI), nongovernmental organizations (NGOs), universi-ties, government mining industries (CODELCO, ENAMI), and private mining industries (EI Indio, La Escondida, La Candelaria, Fachinal, etc). These reduc-tion efforts within the last 10 years exceed $900 million, and in the private

Mercury in Chile 17

mmmg sector alone more than 1,100 monitoring stations have been installed and more than 100,000 environmental measurements have been carried out each year. Furthermore, an important educational program on the use of mercury has been implemented in the small mining area to decrease contamination to the air, water, and soil.

However, the consequences of mercury accumulation are seen in their dam-aging effects to the rivers that deliver water to crops and cities, in the bays where food is extracted, and in the air of some cities where there exist mills that release chemical substances into the atmosphere.

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Manuscript received May 28. accepted June 3, 2003.

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