Environmental Contaminants - PowerPoint Presentation

Slide1

Environmental ContaminantsSlide2

Dioxins and PCBs

What are Dioxins and PCBs?

Dioxins are

colourless

,

odourless

organic compounds

containing carbon, hydrogen, oxygen and chlorine.

There are

many different dioxins

, of which 17 are known to be toxic to humans.

The most toxic known dioxin is

“2,3,7,8-tetra-chloro-di-benzo-p-dioxin (2,3,7,8-TCDD)”

Significant concentrations of this compound can be measured in

parts per trillion (PPT

).

Slide3

Dioxins

are ubiquitous environmental contaminants, having been found in:

Soil

Surface water

Sediment

Plants

Animal tissue

They are highly persistent in the environment with

half-lives ranging from months to years.

They have

low water solubility

, meaning that they

remain in soil and sediments that serve as

environmental reservoirs

from which the dioxins may be released over many years.

Slide4

PCBs (poly-chlorinated biphenyls)

are

chlorinated aromatic hydrocarbons

produced by the

direct chlorination of biphenyls

.

There are

about 209 related PCBs

, known as congeners of PCBs, of which 20 reportedly have toxicological effects.

Some of the

PCBs have toxicological properties similar to those of dioxins

and are therefore often referred to as

‘‘dioxin-like PCBs’’.

Like dioxins, PCBs are widespread environmental contaminants and are very

persistent in soil and sediments.

It has been suggested that highly contaminated bottom

sediments in sewage

and

receiving streams

may represent a

reservoir

for the continued release of

PCBs into the environment.

Slide5

Occurrence in Foods

Grazing animals

and

growing vegetables

may be

exposed directly, or indirectly, to these contaminants in the soil

.

Leafy vegetables

and

pasture

can also

become contaminated through airborne transport of dioxins and PCBs.

Dioxins

in

surface waters and sediments

are

accumulated by

aquatic organisms

and

bioaccumulated

through the food chain

.

The

concentration of dioxins in fish

may be

hundreds to thousands of times higher

than the concentrations found in surrounding water and sediments.Slide6

Because

dioxins

are

not very soluble in water

, they tend to

accumulate

in the fatty tissues

of animals and fish

.

Theoretically,

the longer the lifespan of the animal, the longer the time it has to accumulate dioxins and PCBs.

Foods

that are

high in animal fat

, such as

milk

,

meat

,

fish

,

eggs

and related products are the

main source of dioxins and PCBs

and

contribute about 80% of the overall human exposure

, although almost all foods will contain these contaminants at some (generally very low) level owing to their ubiquitous nature.

Slide7

The

main contributors to the average daily human intake of dioxins and PCBs

have been found to be:

milk and dairy products

, contributing between

16 and 39%;

meat and meat products

, contributing between

6 and 32%

fish and fish products

, contributing between

11 and 63%.

Other foods

, mainly vegetables and cereals, contributed

6–26%

Human milk

can contain elevated levels of dioxins

, some of which can pass to the infant during lactation. Slide8

Effects on Health

Humans

accumulate dioxins in

fatty tissue

mostly by eating dioxin-contaminated foods.

Dioxins and PCBs

have a broad range of toxic and biochemical effects, and some are classified as human

carcinogens

.

In

animal testing

, dioxins have been implicated in causing

damage to the immune and reproductive systems

, developmental effects and

neuro-behavioural

effects

.

The

most commonly observed adverse health effect

in

humans

following

acute over-exposure

to dioxins and PCBs is the

skin disease

chloracne

, a particularly severe and prolonged

acne-like skin disorder

. Slide9

Sources

Dioxins

are often

man-made

contaminants

and are formed as unwanted

byproducts of industrial chemical processes

, such as the manufacture of paints, steel, pesticides and other synthetic chemicals, wood pulp and paper bleaching, and also in emissions from vehicle exhausts and incineration.

Dioxins

are also produced

naturally

during

volcanic eruptions

and

forest fires

.

Most industrial releases of dioxins are strictly controlled under pollution prevention and control regulations.

Currently,

the major environmental source of dioxins

is

incineration

.

Slide10

Stability in Foods

Dioxins and PCBs

are

highly stable

with reportedly

long half-lives.

In

animals

, they

accumulate in fat

and in the

liver

and are only very

slowly

metabolised

by oxidation

or reductive

dechlorination

and conjugation.

They are therefore likely to

persist in animal tissues

, especially fatty tissue, for long periods.

They

are not

generally affected significantly by food processing

such as

heat treatments

, or

fermentation

.

Slide11

Control Options

It is generally agreed that the

best means for preventing dioxins and PCBs

from entering the food chain

is to control their release into the environment.

The

EU

has

prohibited the use of most PCBs

from 1978 and for certain applications from 1986. Slide12

Product Use

While studies suggest that there is no cause for alarm from potential health issues concerning dioxins in the diet, may

help to

minimise

any potential exposure of consumers to

dioxins in food

:

choosing leaner cuts of meat

removing the skin from chicken

trimming the fat off meat

drinking reduced- or low-fat milk

washing of fruit and vegetables to remove any airborne dioxin-contaminated dust particlesSlide13

Legislation

New EU regulations on contaminant levels in foods have recently been introduced.

These new regulations will require tougher safety controls in food-manufacturing plants.

The regulations aim to ensure a

harmonised

approach to the enforcement of permitted contaminant levels across the EU.

Regulation (EC) 1881/2006 sets maximum levels for certain contaminants, including dioxins and dioxin-like PCBs in foods. Slide14
Slide15

Heavy Metals

What are Heavy Metals?

The term ‘‘heavy metal’’ refers to any relatively

high-density metallic element

that is toxic or poisonous

even at low concentrations.

Heavy metals

are

natural components of the earth’s crust

and

cannot be destroyed

.

Although there are many elements that are classified as heavy metals,

the ones of most concern

,

with respect to their

biotoxic

effects and presence in food

, are:

arsenic

Cadmium

Lead

mercurySlide16

Occurrence in Foods

1- Arsenic

The

major source of arsenic

in the diet is from

fish and other seafood

, although the

daily intake is estimated to be less than 0.35 mg.

The

marine environment

has a

great impact on arsenic levels

as

sea fish

have arsenic levels about 10 times higher than

freshwater fish

.

Children have a lower intake of arsenic than adults, and young

children have the lowest intake.

Slide17

2-Cadmium

None of the most commonly consumed foods

were found to be high in cadmium.

Cereals

,

fruit

and

vegetables

are the

main source of cadmium

in the diet, making up

about 66% of the mean cadmium intake

.

The

other sources (Less important)

include:

meat

Fish

Liver

Kidney

molluscs

Children have a lower intake of cadmium than adults, and

young children have the lowest intake

.

Slide18

3-Lead

None of the most commonly consumed foods

were found to be high in lead,

although some Member States reported high lead levels in

meat

and

fish.

Children have a lower lead intake than adults

.

Slide19

4-Mercury

The

main source

of mercury in the diet is

fish

,

followed by

fruit

and

vegetables

.

In fish and shellfish

,

mercury is present in the form of

methylmercury

, while

in most other food groups

it is present in

its inorganic form

.

Methylmercury

is formed from inorganic mercury

by the

action of micro-organisms in marine and freshwater sediments

.

Predatory species of fish

at the top of the food chain

,

such as tuna

, generally

contain higher levels of mercury

, but

their contribution to total mercury intake is small as consumption levels are low

.

Fruit

,

mushrooms

and

vegetables

are

other sources

of mercury.

Although

children have a low total intake of mercury than adults

,

they also have a lower bodyweight and so, potentially, a relatively larger intake/kg bodyweight

. Slide20

Effects on Health

1-Arsenic

Additionally,

inorganic As

3+

salts

are more toxic than

As

5+

salts (Organic arsenic ).

Illnesses associated with excessive

inorganic arsenic

intake include:

skin

lung

heart conditions

gastrointestinal diseases

possible carcinogenic effects. Slide21

Organic arsenic

does not cause cancer, nor is it thought to damage DNA, but exposure to high doses may cause

nerve injury

and

stomach problems

.

However, the

majority of arsenic in seafood

is present in the

organic

,

less toxic form

, and

during digestion of such compounds, the arsenic is not released, or is released only very slowly.

This explains why very few cases of arsenic poisoning are associated with seafood consumption

, despite the high levels observed.

Slide22
Slide23

2-Cadmium

Human intake of cadmium occurs mostly through

food

or through

smoking

.

In humans,

long-term exposure

may lead to

kidney damage

, as

cadmium tends to accumulate in the kidneys

.

Other adverse health effects

include:

Diarrhoea

Stomach pains

Bone defects

Immune-system damage

possible damage to DNA and carcinogenic effectsSlide24
Slide25

3-Lead

Lead enters the human body via

food

,

water

and

air

.

Its

adverse effects

include:

disruption of

haemoglobin

synthesis

kidney damage

increased blood pressure

Miscarriage

nervous-system disruption

reduced fertility

learning disabilities and

behavioural

problems in children. Slide26
Slide27

4-Mercury

It is highly toxic and can cause:

disruption of the nervous system

Brain damage

damage to DNA and chromosomes

allergic reactions

adverse reproductive effectsSlide28
Slide29

Stability in Foods

Heavy metals

are

stable elements

and

persist for long periods in the environment.

There is

no evidence to suggest that levels of heavy metals in foods are changed significantly by processing

.

For example

,

methylmercury

can be found in canned fish that has undergone a severe thermal process.

Slide30

Control Options

Control of heavy metal levels in foods relies largely on

avoiding those food commodities that are likely to have been exposed to large concentrations

of metal contaminants in the primary production environment.

Examples

include

vegetables and produce grown in soils contaminated

naturally, or by industrial activity, and

large predatory fish. Slide31

It is also important to ensure that heavy-metal contamination cannot arise from the use of inappropriate food processing equipment.

Manufacturers must ensure that all equipment is constructed from ‘‘food grade’’ materials that meet the required standards.

Regulations in many countries set maximum levels

for heavy-metal contaminants in certain foodstuffs.

It is the responsibility of manufacturers to ensure that these limits are observed, and that ingredients are sourced from reputable suppliers.

It is also important to ensure that

all processing water is sourced from potable supplies that are not contaminated with heavy metals.

Slide32
Slide33
Slide34
Slide35

Perchlorate

What is

Perchlorate

?

Perchlorate

is:

a chemical that occurs naturally and is also manufactured.

very soluble in water

stable under most environmental conditions

very mobile in most media

has been

recognised

in the United States as an emerging contaminant, mainly associated with industrial activity and space exploration.

Owing to this, there has been increasing interest in the levels of

perchlorate

in soil, groundwater, drinking water, irrigation water and food.Slide36

The

perchlorate

anion

consists of a chlorine atom surrounded by four oxygen atoms

perchlorate

anion

is a

very strong

oxidising

agent

.Slide37

Occurrence in Foods

During 2004, the US FDA (Food and Drug Administration) conducted an initial survey investigating

the

perchlorate

levels in a variety of products

, including:

Milk (more important)

bottled water (more important)

lettuce

tomatoes

carrots

spinach

melonsSlide38

Effects on Health

Exposure to high doses of

perchlorate

has been found to

interfere with iodine uptake into the thyroid gland

.

Perchlorate

appears to r

emove an iodine ion from a protein that transports the iodine to the thyroid

, leading to

iodine deficiency.

This, in turn,

disrupts thyroid development and function

, and may lead to a

reduction in thyroid production

.

The

thyroid

plays an essential role in regulating metabolism

, and in the

developing

foetus

and in infants

, thyroid hormones are essential for normal

growth and development

of the nervous system.

Pregnant women and their unborn children

are therefore at the

greatest risk of iodine deficiency

.

Slide39

Sources

The

highest levels of

perchlorate

contamination

are found in

water and soil near military installations and around the industrial plants

where the chemical is manufactured

.

Perchlorate

is thought to

enter plants when they are irrigated with

perchlorate

- containing water

, or when they are cultivated in soil containing natural

perchlorate

or

perchlorate

-containing

fertilisers

or water.

Slide40

Stability in Foods

Perchlorate

is very

soluble in water

, s

table under most environmental conditions

and

very mobile in most media

.

Because of its high water solubility and stability

,

it tends to accumulate in foods that have a high water content

,

such as cucumbers, melons and tomatoes,

when they are grown in soils contaminated with

perchlorate

or irrigated with

perchlorate

-contaminated water.

Slide41

Control Options

Control is currently

centred

on

reducing contamination of soil and water with

perchlorate

.

Biological remediation

appears to have the most promise for dealing with contaminated sites

.

Some bacteria possess

perchlorate

reductase

enzymes

,

which could possibly be used to treat contaminated water

, although, currently, systems involving the use of these micro-organisms have not been

commercialised

and are not used by US water authorities.

Commercial anion-exchange systems

also offer promise for treating

perchlorate

-contaminated water.

Slide42

Legislation

The

US Environmental Protection Agency

has recommended a

safe level for

perchlorate

in

drinking water

of

24.5 mg/

litre

, but suggests that a safe level for

babies

should be

4.0 mg/

litre

.Slide43

Reference

:

Lawley

R., Curtis L. and Davis J. The food safety hazard guidebook. RSC Publishing.