ENVIRONMENTAL
TOXICOLOGY OF CHROMIUM
EM/2012/017
A.L. Savinda Heshani
OUTLINE
• Properties and oxidation states
• Essentiality of Chromium
• Potential sources
• Exposure routes
• Toxicokinetics
• Mechanisms of toxicity and carcinogenicity
• Toxic symptoms
• Standards and regulations for Chromium
• Historical cases of poisoning
PROPERTIES OF CHROMIUM
• Chromium is a hard, steel-gray metal highly resistant to oxidation
even at high temperatures.
• one of the most abundant metals in the earth’s crust, combined
with iron and oxygen in the form of chromite ore (FeCr2O4).
OXIDATION STATES OF CHROMIUM
• series of oxidation states from −2 valence to +6.
 Elemental Chromium (0)
Trivalent Chromium (+3)
Hexavalent Chromium (+6)
ESSENTIALITY OF CHROMIUM
• Chromium (III) is considered as an essential metal.
• Biologically active Cr(IlI) facilitates the action of insulin.
• Chromium deficiency results in impaired glucose tolerance.
• The estimated safe and adequate daily dietary intake for adults and
adolescents is
50-200 /µg/day
(National Research Council, Food and Nutrition Board, Washington,
DC,1989)
• The daily minimum population mean intake
~33 μg/person (WHO)
• Adequate Intakes (AIs) for Chromium
Source: Institute of Medicine, Food and Nutrition Board, Washington, DC, 2001.
SOURCES OF CHROMIUM
• Natural sources
• chromite ore is in the trivalent state (FeCr204)
• Marine/ terrestrial volcanic eruption
• Anthropogenic sources
3 basic industries
 metallurgical
 chemical and
 refractory (heat-resistant applications)
• In the metallurgical industry
-Metal joint prostheses used in clinical orthopedics
• In the chemical industry
- primarily in paint pigments
- chrome plating
- leather tanning
- wood treatment
• Smaller amounts are used in
- water treatment
- catalysts
- safety matches
- copy machine toners
- corrosion inhibitors
- photographic chemicals
- magnetic tapes
• Refractory uses of chromium include
-magnesite-chrome firebrick
- granular chromite
EXPOSURE ROUTES OF CHROMIUM
• The entry routes of chromium into the human body are;
-inhalation (Inhalation of chromium-containing aerosols)
-ingestion (contaminated food and water)
-dermal absorption (contact)
TOXICOKINETICS OF CHROMIUM
• Major factors governing the toxicity of chromium
compounds are;
-oxidation state
-solubility
-nature of its ligands
• Toxicity of
Chromium (VI) compounds > Chromium(III) compounds
• This differing toxicity may be related to
-permeability of Cr (VI) through cell membranes
-subsequent intracellular reduction to reactive intermediates
Cellular uptake and reduction of Chromium compounds
• The bronchial tree is the primary target organ for carcinogenic
effects of chromium(VI).
• Following oral exposure, absorption of chromium in the
gastrointestinal tract is low.
• In the stomach,
Chromium(VI)
Chromium(III)
• Chromium(III) and chromium(VI) can penetrate human skin to
some extent, especially if the skin is damaged.
• Chromium transported by the blood is distributed to other
organs, the most significant retention being found in the
spleen, liver and bone marrow.
MECHANISMS OF TOXICITY AND
CARCINOGENICITY
• In both animals and humans, elimination of absorbed chromium from
the body is biphasic,
- rapid phase (clearance from the blood)
- slower phase (clearance from tissues)
• Primary route of elimination – urinary excretion (~50%)
• Minor routes
- faecal excretion (5%)
- bile
- transfer to hair and nails
- sweat
• The remaining chromium is deposited into deep body
compartments, such as bone and soft tissue.
• The estimated half-life for whole-body chromium elimination
chromium(VI) – 22 days
chromium(III) – 92 days
TOXIC EFFECTS OF CHROMIUM
• In general, chromium(VI) compounds are more toxic than
chromium(III) compounds.
• Health effects of chromium compounds can vary with route
of exposure, with certain effects specific for the portal of
entry.
• Acute poisoning
• chronic poisoning
oral route
mainly from inhalation or skin contact
• Effects of chromium are not limited to the portal of entry,
hematological, immunological, and reproductive systems also
identified as targets for chromium.
Chromium (VI)
• The primary effects associated
chromium(VI) compounds are;
-respiratory
-gastrointestinal
-dermal
-immunological
-hematological
-reproductive
-developmental
with
exposure
to
• Respiratory effects
• Acute exposure causes;
nasal and lung irritation, altered pulmonary function,
dizziness, headache, coughing, wheezing, sneezing
• Intermediate-and chronic exposure causes;
epistaxis, chronic rhinorrhea, nasal itching and soreness,
nasal mucosal atrophy, perforations and ulceration of the nasal
septum, bronchitis, pneumoconiosis, decreased pulmonary
function, and pneumonia
Perforation of the nasal septum from
Chromium(VI) exposure
• Gastrointestinal effects
• Acute exposure causes;
abdominal pain, vomiting, gastrointestinal ulceration,
hemorrhage and necrosis, and bloody diarrhea.
• Chronic exposure causes;
oral ulcer, diarrhea, abdominal pain, indigestion, and
vomiting, epigastric pain, irritation, and ulceration
• Dermal effects
• Acute exposure causes;
skin burns
• Skin contact with chromate salts may cause;
irritation, burns, allergic type of
dermatitis rashes, untreated ulcers or sores
• Renal effects
-Acute Cr (VI) exposure - renal tubular necrosis
-Chronic exposure results in transient renal effects
• Hepatic effects
-Acute chromium exposure - hepatic necrosis
• Hematological effects
-microcytic
-hypochromic anemia
• Characterized by
-decreased mean cell volume (MCV)
-mean corpuscular hemoglobin (MCH)
-hematocrit (Hct)
-hemoglobin (Hgb)
• Reproductive effects
-effects on male reproductive organs
decreased sperm count and motility
histopathological change to the epididymis
-effects on females
complications during pregnancy and childbirth(toxicosis
and postnatal hemorrhage)
• Immunological effects
-Chromium sensitization
• Developmental effects
• No studies regarding developmental effects in humans after exposure to
chromium compounds.
• A number of oral exposure animal studies have shown
-postimplantation loss
-decreased number of live fetuses
-decreased fetal weight
-internal and skeletal malformations
-delayed sexual maturation in offspring
• Genotoxic effects
-DNA strand breaks
-chromosome aberrations
-increased sister chromatid exchange
-unscheduled DNA synthesis
-DNA-protein crosslinks
• Carcinogenic effects
-increased risk of respiratory system cancers, primarily
bronchogenic and nasal
-increased incidence of liver, lung, and kidney and
urogenital organ cancers
• According to the International Agency for Research on Cancer (IARC);
- Chromium[VI] is carcinogenic to humans (Group 1)
-Metallic Chromium and Chromium[III] compounds are not
classifiable as to their carcinogenicity to humans (Group 3)
• According to USEPA;
-Chromium(VI) - known human carcinogen by the inhalation route
of exposure.
EFFECTS OF CHROMIUM ON PLANTS
• Chromosomal abberations
• Disruption of mitosis
• Cell cycle arrest
• Polyploidization
• Reduced seed germination
• Chloroplast disorganization
• Reduced photosynthesis
• Decreased chlorophyll
• Decreased nutrient uptake, water potential
• Changes in enzymatic activities
• DNA damage
• Inhibition of electron transport processes
EFFECTS OF CHROMIUM ON AQUATIC ORGANISMS
• Chromium toxicity depends on biotic and abiotic factors.
• Biotic factors consist of
-age
-developmental phase of an individual
-type of species
• Abiotic factors comprises
-concentration
-oxidation state of Cr
-temperature
-pH
-alkalinity
-hardness
STANDARDS AND REGULATIONS FOR CHROMIUM EXPOSURE
AGENCY
ACGIH
FOCUS
LEVEL
Air-Workplace 50µg/m3
NIOSH
Air-Workplace 1 µg/m3
COMMENTS
Advisory; TWA to avoid
carcinogenic risk from certain
insoluble chromium compounds
Advisory; TWA (10-hour) for
carcinogenic Cr (VI) salts
25 µg/m3
TWA (10-hour) for noncarcinogenic
Cr (VI) salts, including chromic acid
50 µg/m3
15-minute ceiling limit for
noncarcinogenic Cr (VI) salts
Continued……
OSHA
Air-Workplace 100 µg/m3 Regulation; PEL for chromic acid and
chromates (ceiling)
500 µg/m3 PEL for soluble chromic salts (8-hour
TWA)
1000 µg/m3 PEL for chromium metal and
insoluble salts (8-hour TWA)
EPA
AirN/A
Environment
Drinking-Water 50 µg/L
Under review
Regulation; current MCL for total
chromium; proposed MCL is 100
µg/L
SRI LANKAN STANDARDS
• According to gazette extraordinary of the democratic socialist republic of
Sri Lanka - 01.02.2008
• Tolerance limits for the discharge of
Parameter
Industrial effluents in to inland surface waters
Unit type of Tolerance
limit
Limit values
Chromium, total (as Cr)
mg/1, max.
0.5
Chromium, Hexavalent
(as Cr6+)
mg/1, max.
0.1
Industrial waste discharged on land for irrigation purpose Chromium , total (as Cr)
mg/1, max.
1.0
Industrial and domestic waste discharged into marine
coastal areas
Chromium, total (as Cr)
mg/1, max.
2.0
Chromium, Hexavalent
(as Cr6+)
mg/1, max.
1.0
Continued……
Parameter
Waste from textile industry being discharged Chromium total (as Cr)
into inland surface waters
Hexavalent
Cr+6)
Chromium
Waste from being discharged from tanning Chromium total (as Cr)
industries - to inland surface waters
Hexavalent
Cr+6)
To marine and coastal areas
Chromium
Chromium total (as Cr)
Hexavalent
Cr+6)
Chromium
Effluents into public sewers with central Chromium total (as Cr)
treatment plants
Unit type of
limit
Tolerance
Limit values
mg/1, max.
2.0
(as mg/1, max.
0.5
mg/1, max.
0.5
(as mg/1, max.
2.0
mg/1, max.
0.5
(as mg/1, max.
2.0
mg/1, max.
2.0
HISTORICAL POISONING OF CHROMIUM
Hinkley groundwater contamination
• Hinkley groundwater contamination refers to Pacific Gas and
Electric Company (PG&E) dumping "roughly 370 million gallons"
of chromium-tainted wastewater" into unlined wastewater
spreading ponds around the town of Hinkley, California, located
in the Mojave Desert from 1952 to 1966 and the ongoing process
of restitution and clean-up.
• PG&E used chromium VI one of the cheapest and most efficient
commercially available rust suppressors in their compressor
station for natural gas transmission pipelines.
• Just north of California State Highway 58, the residents continue to
face concerns over chromium (VI) in their well water from the
world's largest plume of this cancer-causing chemical.
• Samples taken in August 2010 showed that the plume of
contaminated water had started to migrate into the lower aquifer.
• As of September 2013, the Cal/EPA reports that the plume has
expanded to 6 miles long and 4 miles wide.
• In 2015 the California Regional Water Quality Control Board, Lahontan
Region served the PG&E with a new order "to cleanup and abate the
effects of the discharge of chromium waste or threatened pollution or
nuisance."
• By the time of the report the plume was "8 miles in length and
approximately 2 miles in width, throughout the Hinkley Valley and into
Harper Dry Lake Valley.
• By 2013 PG&E had spent over $750 million on
remediation.
Chromium poisoning in Noraiakheda area of Kanpur (2004)
• Kanpur was one of the most industrialized towns of Northern India.
• These industries have been poisoning the groundwater resources of the
town over the years.
• The highly polluting industries of Kanpur have rendered the groundwater
in their respective areas unsafe and unusable.
• The communities are totally
dependent on the groundwater
for their water needs.
• People have no choice but to
consume the highly chemicalised
and poisoned water.
• Noraiakheda is one of the areas in
Kanpur where the groundwater
has been reported to be heavily
contaminated with Chromium and
other toxicants.
• The groundwater of the area was reported to be laced with high
concentration of
• Chromium (6.2 mg/l)
• Iron (351.8 mg/l)
• fluorides (4.2 mg/l) and
• pesticides (Lindane 83.47 ng/l,
• DDT (192.36 ng/l)
for the first time in 1997 by Central Pollution Control Board (CPCB)
• The concentrations of Chromium 125 times greater than the desirable
limits for drinking water.
• People in the area get drinking water through hand and submersible pumps
from a depth of 60 ft to 120 ft that is absolutely unsafe for drinking.
• Some of the hand pumps spew yellowish and greenish water.
• Health effects are clearly visible amongst the local population.
• The symptoms of chromium poisoning have started surfacing and undoubtedly
an epidemic is under way.
• People are afflicted with various skin problems and stomach ailments.
• The chromium pollution is impacting the public health, the environment and
the economy.
Yunnan’s chromium trail
• 5,000 tonnes of toxic chromium tailings were dumped near a Yunnan
reservoir, contaminating water supplies and resulting water pollution killed
fish and livestock, endangered the drinking water of tens of millions of people
and attracted widespread media attention across China.
• Residents of Yuezhou township, Qujing city, are in despair: their well water
has turned yellow, their livestock were dying and their crops were withering.
• For months, chemical waste illegally dumped near the shores of
Chachong Reservoir, in this corner of Yunnan province, south-west
China, was quietly poisoning the community's main water supply.
• Rainwater, contaminated after falling on piles of poisonous chromium
tailings, flowed into the 300,000 m3 reservoir, turning it toxic.
• Levels of deadly hexavalent chromium peaked at over 200 times
permitted levels.
• Three main crops in Yangqiying and Zhaishang villages were
affected:
-tobacco leaves turned yellow and speckled
-rice and corn showed poor growth.
• The authorities quickly identified the hazardous waste as
chromium tailings dumped by Luliang Chemicals.
• This company claims to be Asia's largest producer of the
chemical compound menadione, or vitamin K3.
• It is also one of Asia's largest manufacturers of chromium salts:
each year, it produces tens of thousands of tonnes of them.
• Chromium tailings are a waste product from the manufacturing
of chromium salts and metallic chromium.
• Cleanup
Cr(VI)
Sodium
metabisulfite
Cr(III)
Alkali
Reduced acidity
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REFERENCES
http://www.euro.who.int/__data/assets/pdf_file/0017/123074/AQG2ndEd_6_4Chromium.PDF
http://www.sciencedirect.com/science/article/pii/S0379073811004956
https://link.springer.com/chapter/10.1007/978-3-642-79162-8_10
https://www.atsdr.cdc.gov/toxprofiles/tp7-c2.pdf
https://www.atsdr.cdc.gov/csem/csem.asp?csem=10&po=11
https://www.nap.edu/read/4795/chapter/23#295
https://www.eea.europa.eu/publications/GH-07-97-595-EN-C2/chapter6h.html
http://www.ievbras.ru/ecostat/Kiril/R/Ecotox/Leo%20Posthuma,%20Glenn%20W.%20Suter%20II,%2
0Theo%20P.%20Traas-Species%20Sensitivity%20Distributions%20in%20EcotoxicologyCRC%20Press%20(2001).
http://www.oregon.gov/deq/Rulemaking%20Docs/cu2016epacrit.pdfpdf
http://www.meduniv.lviv.ua/files/kafedry/bioneorgan/Chemistry/Group_VIB/Group_VIB.htm
https://www.lenntech.com/periodic/elements/cr.htm
http://www.ecofriends.org/reports/043GroundWater.htm
THANK YOU!