Sea Pollution and Human Health
Many waste substances that have been disposed of into the sea
can cause a variety of acute and chronic health conditions. The
concentration, biological form, chemical form, physical form and
survival of these pollutants are all aspects of whether humans
would be exposed to them. There are two major ways in which
humans can be contaminated by these pollutions. The first is
direct contact either through the skin, lungs or by being
digested; swimming in polluted sea water would be a good way of
being contaminated by a direct contact method. The second way is
an indirect way such as consuming plants or animals that have
come from the contaminated area.
Indirect contamination is a significant way in which humans can
be exposed to toxic organic chemical and metals because they can
be bio accumulated in plants and animals that humans consume.
Direct contamination is a less significant way in which humans
can be exposed to toxic organic chemical and metals because they
tend to be in sea water in low concentration. In the case of
pathogens both methods can be significant because only small
numbers of micro organisms to induce disease and because micro
organisms can reproduce in infected animals and the environment.
'Conservative' and 'persistent' pollutants such as toxic metals
and PCB's are broken down slowly if at all, while 'non
conservative' and 'labile' pollutants such as biodegradable or
volatile organic chemicals are rapidly broken down and removed
from the environment. The 'conservative' and 'persistent'
pollutants are the most problematic due to their environmental
persistence enhances their chances of reaching and affecting
humans.
There are three main categories of pollutants in the sea that
can reach and have adverse affects on human health. First toxic
metals such as arsenic, cadmium, lead and mercury, secondly
synthetic organic chemicals such as polycyclic aromatic
hydrocarbons (PAHs), chlorinated hydrocarbons, pesticides
(dioxins), 'specialised' chemicals polychlorinated biphynyls
(PCBs) and thirdly human pathogens such as viruses, bacteria,
fungi and parasites.
Metals are chemical elements and cannot be destroyed, broken
down or degenerated in the environment. Toxic metals that have
been disposed of in the sea have impacts concerning human
health, especially arsenic, cadmium, lead and mercury. These
four metals are particularly of concern because they are known
to be toxic to human health and have been found in high
concentration in river estuaries and the sea. Chromium, selenium
and copper are found in less concentrations but are still of
concern because they are in areas that come in contact with
humans. Consumption of contaminated seafood is the major
indirect route of human exposure to toxic metals. Marine
organisms such as fish, crabs and shellfish bio accumulate these
toxic metals through their gills when swimming and feeding on
matter than have been contaminated. Arsenic, cadmium, lead and
mercury can cause acute and chronic conditions including
gastrointestinal haemorrhaging, comas, liver and nerve damage,
skin and lung cancer, emphysema, anaemia, kidney, liver,
pancreatic damage, bone damage, blood disorders, reproductive
disorders, eye damage, respiratory impairments and skin lesions.
Organic chemicals are used in industry; these chemicals are used
in pesticides, cosmetics, drugs and food additives. The
behaviour of these chemicals in natural environments vary form
accumulating in organisms to not, from decomposing rapidly when
exposed to light, heat or water to being very resistant and from
being metabolized by other organisms into compounds that are
more or less toxic to resisting bio-degradation. Like toxic
metals, organic chemicals have direct and indirect routes to
affect human health, direct through contact with organic
chemicals and indirect by ingesting contaminated animals and
plants. The direct route of contact in the sea is rare as
organic chemicals are only in low concentration; this method
provides no ill effect on human health because of the low
concentrations. Again, as with toxic metals the indirect route
of consuming contaminated seafood would be the most harmful to
human health. Chlorobenzenes, chlorinated pesticides,
chlorinated hydrocarbons and aromatic hydrocarbons have all been
found in seafood. These chemicals all have adverse human health
effects such as causing cancer, skin and liver disorders.
Human pathogens are micro-organisms that are capable of inducing
human diseases. Human pathogens enter the sea from the discharge
of raw sewage, sewage sludge and wastewater effluent from sewage
treatment plants. Pathogens are also found in commercial and
domestic food waste, animal waste and biological waste from
hospitals and laboratories. Many of these pathogens are
discharged to surface waters or sewage treatment plants. In
rural areas, bacterial contamination animal waste, runoff and
poorly treated sewage discharge. The sea itself is a source of
pathogens which occur and propagate naturally in marine waters.
Viruses and bacteria are the most important of waste-borne
agents of human diseases with respect to their concentration in
waste and the environment and to diseases they cause. Both
direct and indirect exposures to humans are significant ways of
effecting human health. This is because only a small number of
organisms are required to induce disease. Evidence has shown
that some bacteria, including known human pathogens can survive
in the sea for up to three months. Many parasites and viruses
are very resistant to environmental destruction. Many human
pathogens appear to survive better in coastal or estuary region
than open ocean. Large areas of coastal or estuarine waters in
the US have been closed to shellfish fishing due to
contamination by sewage borne micro-organisms. Shellfish borne
bacteria diseases have been responsible for typhoid,
paratyphoid, cholera and viral gastroenteritis outbreaks in the
US. Some bacteria diseases such as typhoid have been contracted
by swimming or surfing in water that is contaminated with
sewage. Many scuba divers have been affected by conditions such
as dermatitis, wound infections and enteric illnesses.
In conclusion, it is best to eat fish and seafood that we know
has come from the open ocean or from estuarine and coastal
regions that have not been contaminated from industry or human
waste. It is also wise to participate in water sports in areas
that you know have not been contaminated by sewage or industrial
waste.