Speciation Studies in Soil, Sediment and Environmental Samples

15

CHAPTER

Trace Elements and

Human Health

Mehrdad Gholami

1,

* and Hojatollah Yamini

2

Introduction

Elements which occur in the organism in very small quantities, less than

0.01 percent, are generally referred to as trace elements (Oliver 1997). Trace

elements play very important roles in nutrition and health. There have been

several reports pointing to the correlation of diseases linked to mineral

defi ciency. For instance, in the 1930s, occurrence of goiter in the goiter belt

of the United States was associated with insuffi cient iodine in plants and soil

(Zimmermann 2011, Anderson et al. 2010, White and Zasoski 1999). Another

example is the Keshan disease, widespread and endemic in some areas of

China, leading to myocardial fi brosis and necrosis. In the 1970s, selenium

defi ciency was discovered to be one of the main determinant factors of

Keshan Disease through two main observations: fi rstly, crops in the area had

an extremely low selenium content, and secondly administration of selenium

before establishment of the disease had a salutary effect on the health of

the patients (Hurst 2011, Burk and Lane 1983, Tan et al. 2002). On the other

1

Department of Chemistry, Islamic Azad University, Marvdasht Branch, Marvdasht, Iran.

Email: [e-mail]

2

Department of English, Islamic Azad University, Marvdasht Branch, Marvdasht, Iran.

Email: [e-mail]

*Corresponding author

546 Speciation Studies in Soil, Sediment and Environmental Samples

hand, for many decades, human beings have contaminated the environment

by dumping and emission of trace element species because they thought

this would be harmless due to eventual dilution of contaminations in the

environment. This was a naive idea which overlooked the transformations of

trace element species in the biosphere which can totally alter their behavior.

Trace element species without any doubt affect the food chain. However

this was a grave mistake with lethal consequences since human beings

are contaminated by various harmful trace element species. These species

accumulate in the fl ora and fauna and their concentrations increasing at

accelerating rate and ascending order in the food chain as a result of a process

known as bioaccumulation. As an example, in 1956, the subtle and serious

consequences of methyl mercury exposure became evident in Minamata,

Japan. Minamata Bay was contaminated with mercury and methyl mercury

from a factory manufacturing chemical acetaldehyde. Mercury was used

in the manufacturing process, both mercury and methyl mercury being

discharged into Minamata Bay. The fi sh in the bay accumulated increasing

amounts of methyl mercury, which was subsequently passed to the fi sh-

consuming residents of the area. This was one of the fi rst modern lessons

of the consequences of the bioaccumulation of methyl mercury (Chan

2011, Walker 2010, Gilbert 2005). Another tragic incident in Iraq clearly

documented the fatal effects of maternal methyl mercury exposure. During

the winter of 1971, some 73,000 tons of wheat and 22,000 tons of barley

were imported into Iraq. This grain, pink-colored mercury-coated seed

grain, intended for planting, was treated with various organic mercurials. A

severe drought in Iraq resulted in a loss of seed grain as people struggling

with malnutrition consumed the seed grains. Unfortunately, the illiterate

local population could not realize the English writings and warnings on

the seed bags nor recognize the pink seeds as hazardous. Bread made from

these seeds was pink, tasty, but toxic, particularly for the growing children,

resulting in the hospitalization of some 6530 and death of 459 people at the

time of the study (Bakir et al. 1973, Syversen and Kaur 2012).

Trace elements can be categorized as i) essential elements with

physiological relevance (microelements or micronutrients), ii) elements

which can become toxic at high concentrations and iii) elements that

are intrinsically toxic (Reinhold 1975). Since different organisms have

different nutritional requirements, some elements can be essential for

one organism but toxic to other ones. Calcium, cobalt, chromium (III),

copper, fl uorine, iodine, iron, magnesium, manganese, molybdenum,

potassium, selenium, sodium, and zinc are essential elements. Currently, iron,

zinc, copper, chromium, iodine, cobalt, molybdenum, and selenium are

considered essential for nutrition by the WHO (WHO 2002). Boron, nickel,

silicon, manganese, and vanadium are elements with possible benefi cial effect.

Aluminum, antimony, arsenic, barium, beryllium, cadmium, lead, mercury,