catapult magazine

catapult magazine

Vol 6, Num 4 :: 2007.02.23 — 2007.03.09


Trace elements in the environment

Thousands of years ago, the Greek and then the Roman civilization rose and fell.  Among their many activities, the Greeks and Romans mined ores containing silver and purified them to make currency.  Lead is a contaminant in silver ores, and is removed during the purification process.  In addition, the Romans mined and smelted lead itself, to make water pipes and other items.  During the refining of this silver and lead, some of the lead entered the atmosphere as fine particles, and traveled around the globe.  We know this because arctic ice, which is laid down in layers (one per year), contains elevated levels of lead that correspond to the rise and fall of the Greek and Roman Empires.  The Greeks and Romans left an environmental record of some of their mining activities.  Did the general use of lead and release of lead into the atmosphere adversely affect the health of the Greeks or Romans?  It is hard to say, although lead toxicity is sometimes cited as a contributing cause of the decline of the Roman Empire.  Atmospheric levels of lead (as indicated by lead levels in arctic ice) were low from the time of the Romans until the Industrial Revolution, when they rose again and greatly exceeded levels at the height of Roman lead refining.  Now, with the removal of lead from gas in much of the world in recent decades, levels of lead in the atmosphere have again begun to drop.

So, what about us today?  To what extent is our civilization releasing trace elements like lead into the environment, and what is the effect of this release?  Before we can answer the question, we need to talk about what trace elements are; their sources, where they go, and what effect they have.  Then we can discuss what can be done to minimize the potential impact of these elements on the environment and on human health.

Trace elements are elements (typically metals or metal-like elements) that are present in the living and non-living parts of the environment in trace amounts.   Since they are elements, the building blocks of all chemicals, they cannot break down over time like a pesticide can.  They simply change from one form to another and move around the environment from one compartment to another—from air to soil to plants to animals and so on.  Trace elements can be divided into two groups: essential trace elements, which are required by organisms for survival, and non-essential trace elements, which are frequently consumed and accumulated by living organisms, but are not required.

In the 1500's, Paracelsus, the father of modern toxicology, stated “Sola dosis facit venenum” (only dose determines the poison).  This means that all chemicals are potentially toxic—even ‘normal’ things like salt or caffeine.  When we state that a chemical is toxic, what we mean is that it takes little of it to cause harm. 

Chemicals themselves are not toxic, but potentially toxic.  They become toxic only under certain conditions.  First of all, we need to be exposed to them, by breathing them in, eating them, or less commonly, having them pass through our skin.  Secondly, chemicals are only toxic if we are exposed to them in amounts above a certain level.  A block of lead sitting on a table is not toxic.  On the other hand, a young woman who recently participated in a radio contest died from consuming too much water—in this case the water was toxic, because of the amount the woman drank.  Everyone consumes a little bit of cadmium, lead and mercury each day.  These elements are in the air we breathe and the food we eat.  Thankfully, few people exhibit symptoms of toxicity to these elements.  An issue with many trace elements is that they can be toxic when we are exposed to very small amounts.  Complicating matters are the essential elements like iron, zinc or selenium.  If we consume too little of these, we experience health problems, and if we consume too much, we experience other health problems.

Trace elements are naturally present in the environment.  They are found in ores, in soils, in water, in the atmosphere and in living things.  They move from place to place in a number of ways.  Small particles containing trace elements are added to the atmosphere by fires and windblown dust.  Trace elements are naturally present in small amounts in soils due to the breakdown of the rocks from which the soils were formed, and they are added to soils and water from the atmosphere.  As water runs off soil, it can carry trace elements into water.  Living things accumulate the trace elements from the environment they live in—from soil and water, or from consuming organisms that have consumed trace elements from these media.

In considering the issue of trace elements in the environment, it is clear that some sources are natural, but that we are adding to the amount as we carry out certain activities.  Soil weathering (the natural breakdown of rocks into soil), volcanic eruptions, forest fires, and wind erosion can all increase the amount of trace elements in the part of the environment from which organisms can accumulate them.  Again, this is a mechanism by which we receive the elements our bodies need to function.  Rocks containing iron break down, and the iron can then be accumulated by a plant that we eat, fending off anemia.

The increase in certain industrial activities, however, has taken more trace elements from deep underground—found in coal, oil, and metal ores, and released them into the environment.  Some of these elements bioaccumulate (build up in tissues) in living things over their lifetime.  It is difficult to know how much we can safely ingest if it takes decades to reach a maximum concentration in our body.

Cadmium is one example of a non-essential trace element.  It is naturally present in soil, accumulated by plants and consumed by us, with no evidence that harm is being done.  However, cadmium is added to the atmosphere when coal is burned, and when certain ores are mined and refined.  It is sometimes found as a contaminant in phosphate fertilizers, and is then added directly to agricultural soils.  It is also added to agricultural soils as a contaminant in sewage sludge—the composted stuff produced by sewage plants that is rich in organic matter and plant nutrients.  As a result of all this, cadmium levels in soils and water have been increasing in recent decades, and a lot of effort has gone (and is going) into determining where cadmium comes from, where it goes, and what effect it has on organisms.  For a variety of reasons, these questions are very difficult to answer.  For an idea of current research visit MITHE; this is a network of research scientists, industry and government studying how trace elements move in the environment, and the risk they pose to the environment and to human health.

Except in severely contaminated sites, plants will accumulate cadmium with no negative effects.  It can then bioaccumulate over decades in the animals that eat the plants, building up mostly in the kidneys, where damage can occur once a certain threshold is reached.  Given all the variables involved, it is difficult to know how much cadmium can be safely consumed each day so that kidney damage will be avoided decades later.  Again, there is no evidence that cadmium is harming us.  As an interesting side note, cadmium is readily accumulated by tobacco leaves, and inhaled by smokers, so smokers ingest (via their food) and inhale (via their smoke) twice as much cadmium per day as non-smokers.

So far, the harm caused by trace metals has been isolated to rather unique situations.  The trace elements of greatest concern (due to their relative toxicity and ability to build up in organisms over time) are mercury (Hg), lead (Pb), and cadmium (Cd).  High levels of mercury and lead are known to negatively impact the development of the nervous system.  As mentioned, high levels of cadmium have an adverse affect on kidney function. They are also correlated with the development of certain cancers.  In the 1950s, Cd poisoning was reported in Japan; a faulty wastewater treatment system that was part of a mine released cadmium into a river for 30 years.  As a result, elevated amounts of cadmium were consumed by villagers drinking the water and eating irrigated rice, resulting in kidney failure and weakened bones.  Salts of cadmium, which have vivid colors, were once used to color icing used on pastries—another example of a practice that has been discontinued!  Due to the fact that lead salts also have vivid colors, lead was once routinely added to paint.  Small children eating paint chips (children will chew on anything!) who have had their blood tested have occasionally had abnormally high levels of lead in their blood.  Dust from houses with lead-based paint has also been measured to have elevated levels of lead; this is of concern because this dust is inhaled, giving lead the chance to enter our blood via our lungs. 

A major source of mercury is coal.  Mercury, which is very volatile, is added to the atmosphere as coal is burned.  It then comes out of the air, and is accumulated by organisms, most notably animals.  Mercury is stored in animals’ fat tissues.  Like the other trace elements, mercury travels around the globe, where it builds up in northern regions.  The result of all this is that mercury levels tend to be high in certain fish.  Health Canada recommends that pregnant or nursing mothers and young children limit their consumption of certain fish, since mercury is readily passed to nursing children in breast milk and can adversely impact the nervous system of developing children.  A more tragic story is unfolding in the far north, where fat-rich foods (seal and whale blubber) of the Inuit can have quite high levels of mercury and other contaminants.  This is made more tragic by the limited availability of other healthy food choices, the strong link between food and culture, and the fact that this culture has not benefited much if at all from the use of coal or mercury.

Centers of mining activity are where the environmental effects of mining can be seen.  Mining and refining have occurred in Sudbury, a city five hours north of Toronto, for about a hundred years.  Nickel, zinc, and copper have been processed there with a large negative impact to the local environment.  Deforestation occurred early to fuel the smelting process, and huge amounts of air pollution in the form of sulphur dioxide and trace elements were produced. Modern smelters have been designed to minimize local impact, but now the trace elements released to the environment travel globally.  Since the 1980s, a lot of money and effort has been put into remediating the environment around Sudbury and, as a result, lakes and forests have begun to recover.

It is difficult to know what consumers can do about the increase in trace elements in the environment.  Trace elements are not likely to harm most of us, and the impact on the environment and/or humans is difficult to observe, or is occurring in remote locations.  We all use energy and metals everyday.  As more has been learned about the potential for harm, certain actions have been taken.  Mercury is no longer used as a fungicide.  Lead is no longer used in paints, or in gasoline.  Due to tighter environmental regulations, industries using these elements are less free to dispose of them via sewage, where they end up in sewage sludge and applied to agricultural land, or in lakes and streams to which treated sewage is added.  This has meant that the amount of cadmium and other non-essential trace elements is lower in sewage sludge today than in sewage sludge of a few decades ago.  For years, pressure treated lumber contained arsenic, another non-essential trace element.  Among other uses, the lumber was then used to make play structures for children, who were then exposed to arsenic.  In Canada, the use of arsenic in this process is being phased out. 

One thing we can do is be very careful of how we dispose of items containing trace elements.  Mercury is present in florescent bulbs, and with the increased use of these, more mercury will find its way into landfills unless it is recycled (and I have read that this is beginning to occur). NiCd batteries contain cadmium and should not be disposed of in normal garbage; our local IKEA has a used battery collection bin.  Electronic items (e.g. computer monitors) often contain potentially toxic trace elements.  And, since mercury is in coal, careful use of electricity, or a switch away from using coal to generate electricity will mean less mercury will end up in the atmosphere.  If you live in an older home with lead based paint, simply adding an additional layer of paint covers over the lead.

As Christians, we are called to love God with all our hearts, minds, strengths, and souls, and to love our neighbors as ourselves. With respect to trace elements, this means making careful use of them and of the products that contain them.  We must minimize the release of these to the point where harm is not caused to other humans, or to the rest of the environment.  To do this, we have to be aware of these elements, of the harm that they can cause, and of how they are released. Let us not benefit from the use of products that contain trace elements if it is done at the expense of others or of the environment.

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