1. HEAVY METALS
(IAQ)

2. Introduction Heavy metals are toxic to human health
Most common heavy metals are lead(Pb), mercury(Hg), cadmium(Cd) and arsenic(As)
Indoor concentration of heavy metals is generally less than their outdoor concentration
They are mainly produced by industrial activities, and deposit slowly in the surrounding water and soil

3. Properties of heavy metals
They occur near the bottom of the periodic table
Have high densities
Toxic in nature
Nondegradable
Note: Arsenic is not actually a metal but is a semimetal i.e. its properties are intermediate between those of metals and nonmetals.

4. Transport phenomenon Water Food Air
Adsorption or absorption onto various materials
Example: Over half of the heavy metal input into Great Lakes is due to deposition from air.

5. Toxicity of heavy metals
Mercury is highly toxic in vapor form but lead,cadmium and arsenic are more toxic in their cationic form
Toxicity arises from strong affinity of the heavy metal cations for sulfur
Medicinal treatment for heavy metal poisoning is done by chelation therapy by administering compounds known as chelates
Example : British Anti-Lewisite(BAL), ethylene diamine tetra acetic acid(EDTA).

6. Toxicity of trace heavy metals
Route of Entry
Toxicity Effect
TWA by
ACGIH
(mg / m³)
Carcinogen (suspected by NIOSH)
Arsenic
Inhalation and ingestion
Irritation of respiratory system, Liver and Kidney damage, Loss of appetite, nausea and vomiting etc
0.20
Yes
Cadmium
Lung, liver and kidney damage; Irritation of respiratory system
0.05
Chromium
Inhalation, ingestion, and absorption through skin
Lung damage and Irritation or respiratory system
0.5

7. Toxicity of trace heavy metals
Route of entry
Toxicity Effect
TWA by ACGIH
(mg / m³)
Carcinogen (suspected by NIOSH)
Mercury
Inhalation,ingestion and absorption through skin
Irritation of respiratory system; lung, liver and kidney damage
0.05
(vapor)
Yes
Lead
Inhalation and ingestion
Lung and liver damage; loss of appetite, nausea etc
0.15 No
Nickel
Inhalation
Lung, liver and kidney damage
1.00

8. Mercury

9. Mercury Most volatile of all metals Highly toxic in vapor form
Liquid mercury itself is not highly toxic, and most of that ingested is excreted

10. Sources of Mercury
Elemental mercury is employed in many applications due to its unusual property of being a liquid that conducts electricity
Used in electrical switches, fluorescent light bulbs and mercury lamps
Emission of mercury vapor from large industrial operations
Unregulated burning of coal and fuel oil
Incineration of municipal wastes
Emissions from mercury containing products :batteries, thermometers, etc.
Mercury amalgams: dental fillings

11. Health effects Skin burns Irritation of nose and skin Rashes
Excessive perspiration
Damage to the kidneys
Damage to vision
Minamata disease
Dysfunctions of the central nervous system
Loss of hearing and muscle coordination
Severe brain damage
Death

12. Concentration of Mercury Vapor Indoors
Location
Mercury Concentration
(mg / m³)
Comments
House 1
21 months after painting with latex paint
Study room
68.2
Living room 69
Bed room 1
66.5
Bed room 2
139
House 2:
164
4 months after painting with latex paint
House 3:
Bed room
262
9 months after painting with latex paint

13. Concentration of Mercury Vapor Indoors
Location
Mercury Concentration
(ng / m³)
Comments
House 4:
Living room
1560
New home, painted with latex paint 30 days before
Office building
203
Doctor’s room
4950
Painted with latex paint 6 months before
Dentist’s office
5550
Hg thermometer broken in the past
1295
Mixing area for Hg-amalgam
Hospital laboratory
307
Inactive for previous 4 days
930
Near the sink
Laboratory
592
Near the desk
398
Office away from laboratory
Source: Foote, 1972.

14. Lead

15. Lead Has a very low melting point of 327 degrees C
Used as a structural metal in ancient times and for weather proofing buildings
Romans used it in water ducts and in cooking vessels
Analysis of ice-core samples from Greenland indicate that atmospheric lead concentration reached a peak in roman times that was not equaled again until the renaissance

16. Sources of lead
Commonly used in the building industry for roofing and flashing and for soundproofing
Used in pipes
When combined with tin, it forms solder, used in electronics and in other applications to make connections between solid metals
Lead is also used in ammunition
Note: Lead shots have been banned in United States, Canada, Netherlands, Norway and Denmark
Lead is used in batteries and sinkers in fishing

17. Sources (contd.) Used in paints
Lead chromate is the yellow pigment used in paints usually applied to school buses. Lead is also used in corrosion-resistant paints and has a bright red color
Used in ceramics and dishware
The leaching of lead from glazed ceramics used to prepare food is a major source of dietary lead, especially in Mexico
In the past, lead salts were used as coloring agents in various foods
Lead is used in some types of PVC mini-blinds

18. Health effects
At high levels, inorganic lead is a general metabolic poison
Lead poisoning effects the neurological and reproductive systems, example: downfall of roman empire
Lead breaks the blood-brain barrier and interferes with the normal development of brain in infants

19. Health effects(contd.)
Lead is observed to lower IQ levels in children
Lead is transferred postnatally from the mother in her breast milk
At elevated levels, lead poisoning would eventually result in death

20. Lead content of House Dust
Activities
Shoes off
Shoes on
Walk-off Mat
After Remodeling
No. of homes studied 5 32 6 9
Home age (yrs) 73 71 76 72
Total amt. Of dust, g / m²
3.5 26
6.7 63
Lead content of dust, ppm
320
780
430
1320
Lead content of soil, ppm
860
1530
1350
2140
Source: Roberts et al., 1990.

21. Facts about lead poisoning
The human groups most at risk of lead poisoning are fetuses and children under the age of seven
Chronic lead poisoning from wine and other sources is one of the factors in the downfall of the roman empire
Episodes of lead poisoning were recorded through the middle ages and even until recent times
A recent study in Mexico indicated that pregnant women can decrease the lead levels in their blood and presumably in the blood of their developing fetus by taking calcium supplements.

22. Cadmium

23. Cadmium
Cadmium lies in the same subgroup of the periodic table as zinc and mercury, but is more similar to zinc
Coal burning is the main source of environmental cadmium
Incineration of wastes containing cadmium is an important source of the metal in the environment
Cadmium is most toxic in its ionic form unlike mercury
Note: Mercury is most toxic in vapor form and lead, cadmium and arsenic are most toxic in their ionic forms.

24. Sources of Cadmium
Cadmium is used as an electrode in “nicad” batteries
Cadmium is used as a pigment in paints(yellow color)
It is also used in photovoltaic devices and in TV screens
Cigarette smoke
Fertilizers and pesticides
Note: The greatest proportion of our exposure to cadmium comes from our food supply- seafood, organ meats, particularly kidneys, and also from potatoes, rice, and other grains.

25. Health effects Severe pain in joints Bone diseases Kidney problems
Its lifetime in the body is several years
Areas of greatest risk are Japan and central Europe
In very high levels it poses serious health problems related to bones, liver and kidneys and can eventually cause death.

26. Arsenic

27. Arsenic
Arsenic oxides were the common poisons used for murder and suicide from roman times through to the middle ages
Arsenic compounds were used widely as pesticides before the organic chemicals era
Arsenic is very much similar to phosphorous

28. Sources of Arsenic Pesticides
Mining, smelting of gold, lead, copper and nickel
Production of iron and steel
Combustion of coal
Leachate from abandoned gold mines
Used as a wood preservative
Herbicides
Tobacco smoke
Wallpaper paste and pigments in wallpaper

29. Health effects Birth defects Carcinogen:
Lung cancer results from the inhalation of arsenic and probably also from its ingestion. Skin and liver cancer, and perhaps cancers of the bladder and kidneys, arise from ingested arsenic
Gastrointestinal damage
Severe vomiting
Diarrhea
Death

30. Recent studies on arsenic exposure
Arsenic emitted from a copper-smelting plant in Bulgaria has been shown recently to have produced a three-fold increase in birth defects in new born children in that area
Most daily exposure of arsenic by north American adults is due to food intake, especially of meat and seafood
Under humid conditions of molds in wallpaper paste and arsenic pigments in wallpaper, instances of mysterious illness and death have been reported

31. Recent studies..(contd.)
4/15/2017
Recent studies..(contd.)
Recent studies have shown that about 1% of Americans consume drinking water that has arsenic levels of 25 ppb or more, and in Utah and California water supplies have been found to contain as much as 500 ppb
Scientists have estimated that there is a one-in-a-thousand lifetime risk of dying from cancer induced by normal background levels of arsenic ( this equals the risk estimate due to tobacco smoke and radon exposure ).
References:-
1) Krishnamurthy, S Biomethylation and environmental transport of metals. Journal of Chemical Education 69(5)
2)Colin Baird Environmental Chemistry, W.H. Freeman and Company, New York.
IAQ

32. General sources of heavy metals in residential houses
Infiltration from outside, along with the dust carried on shoes and clothes
Indoor sources include old-lead and latex based paints, domestic water supply, burning of wood, and tobacco smoke
Pesticides and fungicides are major sources of arsenic and mercury indoors

33. Sampling and Measurement

34. Methods for measurement of trace metals
Most common method of collecting particulate matter is through filters
Identification and concentration of individual trace metals like lead,cadmium, arsenic, mercury and chromium is determined by
 Atomic absorption spectrophotometer
 X-ray fluorescence
 Atomic absorption spectrophotometry is a destructive method and requires at least 1 to 2 ml of solution
 X-ray fluorescence is a nondestructive method and works independent of the chemical state of the sample.

35. Control strategies

36. Control methods
Periodic vacuuming of the house can be effective in removal of these pollutants
Replacement of wood-burning by an equivalent gas or electrical appliance
Removal of old lead and mercury-based paints
The effective method for removal of mercury vapors is by the use of packed bed of absorbents
Gold-coated denuder can also be used for the removal of mercury from air

37. References
Krishnamurthy, S Biomethylation and environmental transport of metals. Journal of Chemical Education 69(5)
Colin Baird Environmental Chemistry, W.H. Freeman and Company, New York.