Zinc

DESIGNATIONS

CAS No.: 7440-66-6
Registry name: Zinc
Chemical name: Zinc
Synonyms, Trade names: Zinc powder; zinc dust, zinc clippings, zinc folings and others
Chemical name (German): Zink
Chemical name (French): Zinc
Appearance: Shiny, bluish white metal with elongated hexagonal lattice. The metal is brittle at ambient temperature. It becomes ductile at temperatures between 100 and 150°C and, above 250°C it is so fragile that it can easily be reduced to powder. Generally marketed as bluish grey powder.

BASIC CHEMICAL AND PHYSICAL DATA

Chemical symbol: Zn
Molar mass: 65.38 g
Density: 7.14 g/cm³(at 20°C), 6.56 g/cm³(at melting point)
Boiling point: 907°C
Melting point: 419.6°C
Vapour pressure: 1.3 x 10^-7Pa at 103.3°C
Ignition temperature: approx. 500°C
Solvolysis/solubility: dissolves in mineral acids with hydrogen being produced

BASIC DATA OF SELECTED COMPOUNDS

CAS No:	1314-13-2	7733-02-0
Chemical name:	Zinc oxide	Zinc sulphate
Chemical name (German):	Zinkoxid	Zinksulfat
Chemical name (French):	Oxyde de zinc	Sulfate de zinc
Appearance:	colourless crystals or white powder	colourless rhombic crystals
Empirical formula:	ZnO	ZnSO₄
Rel. molecular mass:	81.37 g	161.43 g
Density:	5.6 g/cm³	3.54 g/cm³
Melting point:	1975°C	above 600°C decomposition
Solvolysis/solubility:	in water: 1.6 x 10^-3 g/l

ORIGIN AND USE

Usage:
Mainly in alloyed form for castings, for the surface protection (galvanisation) of sheet iron, iron wires and consumer goods such as gutters, buckets, troughs and roofing materials. Zinc alloys contain above all Al and Cu. Both metals considerably enhance the strength of zinc. The addition of magnesium (up to 0.05%) improves corrosion resistance. Zinc is used in mechanical engineering, haulage and the motor vehicle industry. The chemical industry requires large amounts of zinc dust as a reduction agent. In comparison with the metal, zinc compounds play a minor role. The most important compounds are as follows:

- zinc oxide (white pigment, filler for rubber goods, zinc ointments, parent substance for other zinc compounds),

- zinc sulphide (luminous coating on X-ray screens, in white paint),

- zinc sulphate (used in dyes, for the production of lithopones and as an impregnating agent for wood; parent substance for the production of hydrolysed zinc)

Origin/derivation:
Trace element in humans, animals and plants (2-4 g in human body). Zn is the 26th most frequent element. It makes up 0.0058% of the Earth's crust. Zinc ores are very common. They usually contain other metals (e.g. Pb, Cu, Fe, Cd) which considerably influence the economic viability of extraction. Sedimentary deposits result from the weathering of primary layers. The most important zinc minerals are: sphalerite, wurtzite, smithsonite, hemimorphite, wilemite and zincite.

Zinc is chiefly obtained from zinc sulphides; slags containing zinc and blast-furnace dust likewise play a part. The crushed raw material is first enriched by floatation and then converted to oxides with the help of roasting methods. The roasted blends produced are further processed by zinc distillation or electrolytic methods to form metal. Zinc dust is either extracted as a by-product from the zinc distillation process or is obtained through mechanical atomisation by spraying liquid metal.

Production figures:
Extractable reserves are estimated at more than 100 million tons. The principal deposits are to be found in Australia, the USA, Canada, Russia, Peru, Mexico, Japan, Zaire, Zimbabwe, Morocco, Yugoslavia, Spain and Sweden.
Worldwide production totals some 6.4 million t/a.

Emission figures (estimated):
Roughly 314,000 t of zinc were emitted into the atmosphere in 1975, but this figure has been reduced since then. Approximately 100,000 t find their way into the sea every year.

Toxicity

Plants:

Various species	150-200 mg/kg	Reduced yield	acc. BAFEF, 1987
Young barley	120-220 mg/kg	Reduced yield	acc. BAFEF, 1987

Characteristic effects:

Humans/mammals: The inhalation of zinc-oxide vapours causes metal-fume fever with the following symptoms: fever, pain, fatigue, shivering, sweating. Large quantities of zinc salts are corrosive. Acute zinc poisoning can result, for example, from pickled foods stored for lengthy periods in zinc vessels.

Plants: Necrosis, chlorosis, inhibited growth. The phytotoxicity is predominant to the adverse effects in other organisms.

ENVIRONMENTAL BEHAVIOUR

Water:
As zinc forms a protective layer, it is stable both in freshwater and seawater. Zinc powder is highly reactive due to its large specific surface: danger of dust explosion or formation of highly flammable hydrogen.

Air:
A thin colourless layer made up of alkaline zinc carbonates and zinc oxide forms on the surface of the metal and thus prevents further reaction.

Soil:
Accumulation can be established in soil up to a distance of several kilometers from zinc works. Agriculture is impossible in the immediate vicinity of such works.

Degradation, decomposition products, half-life.
When exposed to heat, zinc oxidises to form zinc oxide.

Food chain:
Zinc is taken up by several plants.

ENVIRONMENTAL STANDARDS

Medium/ acceptor	Sector	Country/organ.	Status	Value	Cat.	Remarks	Source
Water:	Drinkw	WHO	G	5 mg/l			WHO, 1984
	Surface	D	G	0.5 mg/l		⁶⁾	DVGW, 1975
	Surface	D	G	1 mg/l		⁷⁾	DVGW, 1975
	Surface	EC	G	0.5 mg/l		Guide value³⁾	acc. LAU-BW¹⁾, 1989
	Surface	EC	G	3 mg/l		Limit value³⁾	acc. LAU-BW, 1989
	Surface	EC	G	1 mg/l		Guide value⁴⁾	acc. LAU-BW, 1989
	Surface	EC	G	5 mg/l		Limit value⁵⁾	acc. LAU-BW, 1989
	Surface	⁹⁾	G	5 mg/l		Limit value⁵⁾	acc. LAU-BW, 1989
	Waste water	CH	G	2 mg/l		Direct/indirect introduction	acc. LAU-BW, 1989
	Waste water	D(BW)	G	5 mg/l			acc. LAU-BW¹⁾, 1989
	Surface	EC	G	0.3 mg/l		Salmonoid weight²⁾	EC, 1978
	Surface	EC	G	1 mg/l		Cyprinid weight²⁾	EC, 1978
	Groundw	D(HH)	G	0.2 mg/l		Further investigation	acc. LAU-BW¹⁾, 1989
	Groundw	D(HH)	G	0.3 mg/l		Rehabilitation	acc. LAU-BW, 1989
	Groundw	NL	G	65 m g/l		Reference	acc. TERRA TECH, 6/94
	Groundw	NL	L	800 m g/l		Intervention	acc. TERRA TECH, 6/94
	Irrigation	USA		2 mg/l (max.)		Contin. irrigation	EPA, 1973
	Irrigation	USA		10 mg/l (max.)		Fine-grain soils, 20a	EPA, 1973
	Marine	USA		0.1 mg/l (max.)		Hazard threshold	EPA, 1973
	Marine	USA		0.02 mg/l (max.)		Minimal risk	EPA, 1973
Soil:			G	0.5-5 mg/kg DS			acc. CES, 1985
			G	130 mg/kg		Available	acc. ICRCL, 1983
		CH	G	200 mg/kg		Total	acc. LAU-BW, 1989
		CH	G	0.5 mg/kg		Available	acc. LAU-BW, 1989
		D	G	300 mg/kg		Tolerance value	acc. LAU-BW, 1989
		D(HH)	G	1,000 mg/kg DS		Further investigation	acc. LAU-BW, 1989
		NL	G	140 mg/kg		Reference	acc. TERRA TECH, 6/94
		NL	L	720 mg/kg		Intervention	acc. TERRA TECH, 6/94
		USA	G	250 mg/kg FS		Available	acc. LAU-BW, 1989
		USA	G	5,000 mg/kg FS		Total	acc. LAU-BW, 1989
	Sew.sludge	CH	L	3,000 mg/kg DS		¹⁴⁾	acc. LAU-BW, 1989
	Sew.sludge	D	L	300 mg/kg		⁹⁾¹²⁾	acc. LAU-BW, 1989
	Sew.sludge	D	L	3,000 mg/kg		¹⁰⁾¹¹⁾	acc. LAU-BW, 1989
	Sew.sludge	EC	G	150-300 mg/kg DS		^9)11)13)	acc. LAU-BW, 1989
	Sew.sludge	EC	G	2.5-4 g/kg DS		¹⁰⁾¹³⁾	acc. LAU-BW, 1989
	Fertilisers	D	L	100 mg/kg		Residual lime	acc. LAU-BW, 1989
	Fertilisers	D	L	<= 5%		Copper fertiliser	acc. LAU-BW, 1989
	Fertiliser	D	L	<= 5%		Co-cu-fertiliser	acc. LAU-BW, 1989
	Compost	A	G	300-1500 ppm DS			acc. LAU-BW, 1989
	Compost	CH	L	500 mg/kg DS		¹⁵⁾
	Compost	D	G	300 mg/kg.		⁹⁾	acc. LAU-BW, 1989
Air:		CH	(L)	400 µg/m³/d		a-average in dust	acc. LAU-BW, 1989
		D	L	50 µg/m³	MIK	a-average	acc. LAU-BW, 1989
		D	L	100 µg/m³	MIK	24-h average	acc. LAU-BW, 1989
Zinc chloride:	Workpl	AUS	(L)	1 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	B	(L)	1 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	CH	(L)	1 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	I	(L)	1 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	NL	(L)	1 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	PL	(L)	1 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	S	(L)	1 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	SF	(L)	1 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	USA	(L)	1 mg/m³		Long/short-time average	acc. MERIAN, 1984
Zinc chromate:	Workpl	B	(L)	0.1 mg/m³		8-h average	acc. MERIAN, 1984
Zinc chromate:	Workpl	NL	(L)	0.1 mg/m³		8-h average	acc. MERIAN, 1984
Zinc oxide (fumes):	Workpl	AUS	(L)	5 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	B	(L)	5 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	BG	(L)	5 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	CH	(L)	5 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	CS	(L)	5 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	CS	(L)	15 mg/m³		Long-time value	acc. MERIAN, 1984
	Workpl	D	L	5 mg/m³		MAK	acc. DFG, 1994
	Workpl	DDR	(L)	5 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	DDR	(L)	15 mg/m³		Long-time value	acc. MERIAN, 1984
	Workpl	I	(L)	5 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	H	(L)	5 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	J	(L)	5 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	NL	(L)	5 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	PL	(L)	5 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	SF	(L)	5 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	S	(L)	1 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	SU	(L)	6 mg/m³		8-h average	acc. MERIAN, 1984
	Workpl	USA	(L)	5 mg/m³		8-h average	acc. MERIAN, 1984
Plants:	Fodder plants	D	G	500 mg/kg (max.)	Poor quality		acc. BAFEF, 1987

Notes:

¹⁾ Baden-Württemberg Regional Environment Office
²⁾ For protection of aquatic organisms
³⁾ For simple physical drinking water treatment and sterilisation
⁴⁾ For normal physical/chemical drinking water treatment and sterilisation
⁵⁾ For physical and refined chemical drinking water treatment, oxidation
⁶⁾ Impact limit up to which drinking water can be produced by natural methods
⁷⁾ Impact limit up to which drinking water can be produced using known chemical/physical methods
⁸⁾ Countries bordering on Rhine
⁹⁾ Content in soil following application
¹⁰⁾Sludge dry residue for spreading on agricultural areas
¹¹⁾Spreading possible with exceeding of limit values, approval required
¹²⁾Values should be reduced for pH values less than 6
¹³⁾Overstepping of values by 10% permitted
¹⁴⁾ Pollutant content in dry residue of sewage sludge. Sewage sludge is not to be applied to saturated, snow-covered soil, moors, hedges, perimeters of forests, banks of surface water, areas where seed is sown and in the catchment areas of groundwater protection zones etc. A maximum of 7.5 t of sewage-sludge dry matter may be spread per hectare in 3 years.
¹⁵⁾Up to 31st August 1991 possible to exceed limit value 3 times

Comparison/reference values

Medium/origin	Country	Value	Source
Soil:
Normal overall content	D	3-50 mg/kg	acc. LAU-BW,¹⁾, 1989
Tolerably contaminated	D	<10-300 mg/kg	acc. LAU-BW, 1989
Especially contaminated	D	up to 2000 mg/kg	acc. LAU-BW, 1989
Air:
Deposition rates:
"Clean-air" zones	D	80 µg/(m² d)	acc. SRU, 1988
Rural areas	D	80-500 µg/(m²d)	acc. SRU, 1988
Conurbations	D	300-several 1000 µg/ (m² d)
Near to source of emission	D	several 10 mg/(m² d)	acc. SRU, 1988
Immission in suspended dust:
Rhine Ruhr (1984)	D	160-470 ng/m³ (mean range)	acc. SRU, 1988
Rhine Ruhr (1984)	D	310 ng/m³ (mean)	acc. SRU, 1988
Stolberg (lead production)	D	800 ng/m³ (a-average)	acc. SRU, 1988
Rural areas	D	£ 0.1 µg/m³
Plants:
Normal content		10-100 mg/kg	acc. CES, 1985

Assessment/comments

As in the case of all other heavy metals, every effort should be made to stop anthropogenic zinc emissions impacting the environment. The hazard to the environment and the health risks involved with zinc are made abundantly clear by the numerous limit values for water. Other zinc compounds such as zinc chloride and zinc oxide are air pollutants and are likewise the subject of numerous regulations. Attention is to be paid to the zinc content as regards agriculture and the spreading of sewage sludge. Cultivation should be discontinued if necessary since zinc can be accumulated by plants and thus result in a human health hazard by way of the food chain.

From an ecological point of view, the assessment is the same as for aluminium, lead, cadmium, thallium etc.

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