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Metals and chemicals are the basis of the metal finishing industry. The toughtkess use, release or

dumping of chemical residues and effluent can effect a wide range of environmental species, as welll

as causing serious human health effect . some effect occur immidiately, others may take some years

to manivet themselves. Often pollution and helath effect are closely limited.

Common process, and the chemicals used are summarized in annex c. It is important to stress that

irrespective of their measured level of toxicity, all chemicals must be treated with respect. Most

chemicals are toxic if their exposure is high enough, and all chemicals in large amounts. Information

on chemical hazards, on pollution and on management option to avoid these effect is now available

through handsbook and information networks.

Most process which involve the use of chemicals should be examined for their propensity to cause

pollution. Loss of chemicals can occur from rinsing operation, from spills, or the discarding of spent

solutions. In a few instances even the products from the industry may be enviromental concern, eg .

object plated with cadmium.

While waste water treatment will greatly reduce quantities of pollutans reaching the environment. It

is also now realized such treatment can itseld lead to some environmental problems if not carefully

done. In some cases the sludges resulting from waste water treatment are consideredhazrdous

wastes- by regularly authorities, die to their high metal concentrations reduction of such secondary

sources of pollution can only be achieved when a comprehensive approach to wate management,

preferably based on waste avoidance principles is adopted withih a company.A number of ancillary operations may also give rise to loss of chemicals to the environment. These

include :

- Storage of chemicals- Transfer and handling of chemicals- Wastewater treatment and discharge- Discharge from process control laboratories- Disposal of residues- Re-use or disposal of empty chemical container

2.2 enviromental effects

Chemical pollutans can cause a wide variety of environmental effects. These effects may vary from

one target species to another, and also depend on the particular pathway that a chemical takes in

the environment. Human are particulary important targets of course, but many other parts of the

environment are also susceptible to the toxic effect of chemicals.

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With respect to the work place it is useful to identify a number of common hazard. Corrosive

chemicals such a acids and alkalis eat away at tissues and materials, eg reaction tanks. Strong

oxidizing agents may cause burns, or cause fires if they come into cntact with paper, packaging

materials, timber, or textiles. Large quantities of flammable materials are fire hazar dan sometimes

cause explosions. Many solvent are flammable.

With respect to human health and animal and plant life, the following terms are often encountered.

Toxicity refers to poisoning of living things and can be immediate (acute), or can manifest itself after

long periods of time (chronic) . many chemicals such as heavy metals tend to gradually accumulate

the body and may begin to show effects only years after exposure begun. Only rarely can sickness

then be prevented form proceeding. Cancer producing properties of chemicals (carcionegenicity)

and their potential to alter genetic codes (mutagenicity) are normally counted among the toxic

properties.

With respect to the environment it is useful to have an understanding of the following terms,

pollutions refer to damage to the environment, or upset pf ecologial system. The routes in the

environment trough which chemicals are distributed are callled enviromental pathways. Chemical

can migrates in the environment from one compartement to the next: eg. From soil into water or

from water into air . some materials and chemicals tend to degrade rapidly in the environment,

others are more or less persistent and can over time migrate to new locations under the influence

of natural force. Mertals tend to adsorb easily on surfaces like soil or sediments and show aconsiderable tendency to geo-accumulate. Many metals also have the abilty to bio-accumulate in

plant or animal tissue. Sometimes they can reach such high concentrations there that consumption

of the contaminated foodstuffs has to be regulated for the reasons of health.

The discharge of untreated metal finishing wastewaters to natural wasteways has contributed to

water poluutions in many industrial region. As well as damaging natural ecosystems, the water has

often become unfit for drinking. Fisheris may be directly destroyed, or their products rendered unfit

for eating. Purification of ater to restore its use is generally expensive.

To reduce problems of local pollution, many authorities provide a public sewerage system for

wastewaters. However if such wastewaters are too concentrated, the discharge into public drains

and sewer can still cause problems. Toxic chemicals can interfere with the purification process of

treatment systems. Heavy metals contained in effluents often accumulate in the biological sewage

sludge. If used as soil conditioners on farms, the contaminated sludge can pass the chemicals on to

food lants or to animal feed. Many public authorities now regulate the discharge of effluents into

the publc sewerage system to avoid such effects.

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The storage and transportation of heavily contaminated sludges or wastewater may also pose some

difficulties due to the composition or consistency of the materials. Hauling equipment and transfer

operations should therefore pay particular attention to these needs.

Altoug many reagents in metal finishing are relatively non volatile , air pollution problem may still be

important. Substansial quantities of acid fumes and mists may be released from some operations.

Certain hazardous gases may be released from process reaction.

The dumping of treatment sludges and chemical water into poorly located, badly constructed or

carelessly managed landfill sites can lead to groundwater pollution problems. Obviously health and

safety problems for workers can also result from such practice.

Hazard from old waste dumps,a bandoned storage and plant sites are now well knowns and

documented in many parts of the world. The high concentration of toxic chemicals sometimes found

there have led to costly excavation programmes in order to prevent continued damage to health

and the environment,

Accident involving chemicals can be very serious matter. Prevention of accidents is far more

effective and less costly than paying for the clean up and damehe after they have occured.

Prevention menas installing equipment that is not accident prone, ensuring safe operating

procedures, and having suitable emergency response procedurs in place. Proper training of

personnnel is essential to ensure safe operating procedures. Recruitment of shop floor personnelshould pay due regard to their need for safety training.

Direct exposure of workers to chemical reagents and fumes can cause a number of long term

illnesess. Severe exposure may cause acute illness, or even death. Unhygenic conditions at work and

eating and smoking in the work place greatly contribute to the chance of exposure.