Environmental Health and Metals

Toxic Metals

  • Include:
    • Heavy metals (e.g., lead, mercury, nickel)
    • Other metallic compounds (e.g., aluminum, iron, tin)
  • Featured in the CERCLA Priority List of Hazardous Substances

CERCLA Priority List of Hazardous Substances

  • Created by Agency for Toxic Substances and Disease Registry (ATSDR)
  • Rank-ordered list of hazardous substances
  • Revised and published on a 2-year basis, with a yearly informal review and revision

Characteristics of Hazardous Substances on the CERCLA Priority List

  • Pose the most significant potential threat to human health
  • Known or suspected toxicity
  • Potential for human exposure at NPL sites
  • Possible for substances with low toxicity but high NPL frequency of occurrence and exposure to be on the priority list

Top 20 Hazardous Substances from the ATSDR 2019 Substance Priority List

  • Arsenic
  • Lead
  • Mercury
  • Vinyl chloride
  • Polychlorinated biphenyls
  • Benzene
  • Cadmium
  • Benzo(a)pyrene
  • Polycyclic aromatic hydrocarbons
  • Benzo(b)fluoranthene
  • Chloroform
  • Aroclor 1260
  • DDT, p, p’-
  • Aroclor 1254
  • Dibenzo(a,h)anthracene
  • Trichloroethylene
  • Chromium, hexavalent
  • Dieldrin
  • Phosphorus, white
  • Hexachlorobutadiene

National Priorities List (NPL)

  • Prioritized by ATSDR and EPA
  • Lists “most serious uncontrolled or abandoned hazardous waste sites in the United States identified for possible long-term remedial action under Superfund”
  • Sites scored based on the Hazard Ranking System and updated at least once a year

Heavy Metals

  • Have a high atomic weight with a specific gravity that exceeds the specific gravity of water by five or more times

Classification of Toxic Effects of Metals

  • Major toxic metals with multiple effects
  • Essential metals with potential for toxicity
  • Metals related to medical therapy

Bioaccumulation

  • Toxic substances such as heavy metals become more concentrated and potentially more harmful as they move up the food chain.

Modes of Exposure to Metals

  • Lungs:
    • Through inhalation of dusts, metal fumes, and vapors
  • Skin:
    • Through contact with dusts
  • Mouth:
    • By ingestion

High- and Low-Level Contacts

  • Contact with high concentrations of toxic metals is most likely to occur in an occupational setting.
    • Example: people who work with metals
  • Lower-level exposures may result from contact with the ambient environment
    • Example: children may ingest toxic metals present in paint

Symptoms of Acute Toxic Metal Poisoning

  • Generally rapid onset of symptoms (few minutes to approximately 1 hour)
  • Symptoms vary depending on portal of entry.
  • Gastrointestinal effects (vomiting and stomach pain)
  • Neurologic effects (headaches, suppression of normal breathing, and convulsions)

Symptoms of Long-Term Exposure at Lower Levels

  • Difficult to differentiate from those of chronic medical conditions
  • Reduced cognitive functioning
  • Learning impairment

Potential Exposure Media

  • Air
  • Soil/dust
  • Water
  • Biota/food

Gender Differences and Heavy Metal Exposure Effects

  • Effects are different for women than they are for men.
  • Differences have been attributed to hormonal and metabolic processes related to menstruation, pregnancy, and menopause.

Fetuses, Infants, and Children and Exposure to Heavy Metals

  • Present serious hazards
  • Impairment of physical and mental development
  • Damage to internal organs and the nervous system
  • Some forms of cancer
  • Mortality

Effects of Exposure to Heavy Metals in Children

  • Nervous system damage
  • Memory impairment
  • Difficulty in learning
  • Range of behavioral problems, such as hyperactivity syndrome and overt aggressiveness

Heavy Metal Exposure among Children versus Adults

  • Have smaller body weight
  • Consume more food in proportion to their body weight
  • Receive higher doses of heavy metals that may be present in food

Fetal Exposure Effects

  • Lead and mercury have the capacity to cross the placental barrier.
  • Can cause potential fetal brain damage

Major Toxic Metals with Multiple Effects

  • Arsenic
  • Beryllium
  • Cadmium
  • Chromium
  • Mercury
  • Lead
  • Nickel

Arsenic

  • Varies in toxicity depending on chemical form
  • By-product of refining gold and other metals
  • Used in pesticides, wood preservatives, and manufacturing processes
  • Exposure can come from ingestion and inhalation.

Standards for Arsenic

  • 2001 EPA standard: 10μg10 \mu g of arsenic per liter of drinking water, with the year 2006 set as the compliance date
  • Prior standard: 50μg50 \mu g of arsenic per liter of water

Potential Health Effects of Arsenic Exposure

  • Skin, bladder, kidney, and liver cancer when ingested
  • Lung cancer when inhaled
  • Peripheral vascular disease
  • Cerebrovascular disease
  • Cardiovascular disease (e.g., hypertensive heart disease)
  • Diabetes (long-term exposure)
  • Adverse pregnancy outcomes
    • Spontaneous abortions
    • Stillbirths
    • Preterm births

Beryllium

  • Used widely in industry because of its special properties (lighter than aluminum and stronger than steel)
  • Employees in the metal processing industry most likely to be exposed
  • Inhalation one of the most common methods of exposure
  • Class A carcinogen

Cadmium and the General Population

  • Primary sources of cadmium exposure for the general population
    • Cigarette smoke
    • Dietary cadmium
    • Bioaccumulates in shellfish
    • Found in some species of mushrooms

Occupational Exposures to Cadmium

  • Production of nickel cadmium batteries
  • Zinc smelting
  • Paint manufacturer
  • Soldering
  • Employment in metal factories

Effects of Cadmium Exposure

  • Osteoporosis in women
  • Height loss in men
  • Kidney damage
  • Elevated blood pressure
  • Cardiovascular diseases
  • “Itai-itai” disease

Chromium

  • Naturally occurring element in the earth’s crust (e.g., in rocks, soils, and materials of volcanic origin)
  • Most common forms:
    • Chromium(0)
    • Chromium(III): an essential nutrient
    • Chromium(VI): classified as a carcinogen

Effects of Hexavalent Chromium(VI) Exposure

  • Ingestion:
    • Digestive problems
    • Damage to organs such as the kidney and liver
  • Topical:
    • Skin ulcers
  • Inhalation in high concentrations:
    • Respiratory problems (e.g., nose bleeds, perforation of the nasal septum, and runny nose)

Hexavalent Chromium [Cr(VI)]

  • One of the valence states (+6) of the element chromium. It is usually produced by an industrial process.
  • Cr(VI) is known to cause cancer. In addition, it targets the respiratory system, kidneys, liver, skin and eyes.
  • Chromium metal is added to alloy steel to increase hardenability and corrosion resistance.
  • A major source of worker exposure to Cr(VI) occurs during "hot work" such as welding on stainless steel and other alloy steels containing chromium metal.
  • Cr(VI) compounds may be used as pigments in dyes, paints, inks, and plastics. It also may be used as an anticorrosive agent added to paints, primers, and other surface coatings.

Erin Brockovich

  • Advocated for residents of Hinkley, California, against a power company accused of polluting the town’s water with chromium(VI)

Mercury

  • Naturally occurring metal
  • Highly toxic
  • Released into the environment as a by-product of industrial processes

Mercury Deposition in Lakes and Rivers

  • Potential hazard to human health even at low levels in water
  • Can increase to high levels
    • Methylation—microorganisms convert elemental mercury into methyl mercury
    • Bioaccumulation—causes mercury levels to become more concentrated in aquatic invertebrates

Legacy of Mercury Contamination

  • Minamata disease
  • Water contamination around the New Almaden mine in California

Lead

  • Sources of environmental lead:
    • Leaded gasoline
    • Tap water from soldered pipes
    • Painted surfaces in older buildings
  • Another common source of household lead:
    • Imported pottery used in food service

Lead in Water

  • The water may be lead-free coming from the reservoirs, but the lines near the homes often contain lead materials (pipes, solder, connections).

Lead Exposure

  • Causes serious central nervous system effects and other adverse health consequences even when ingested at low levels
  • One of the most common environmental pediatric health problems in the US

Flint Water Crisis

  • Lead contamination in Flint, Michigan began with a switch of water supplies from Lake Michigan to the local Flint River to save money

Flint Water Quality

  • Very quickly, although the water tested ok at the source, it began to look bad at the tap

Flint Water Crisis - Pipe Changes

  • The interior surface of the pipes began to change

Flint Water Crisis - Politics

  • Politics intervened and the problem seemed to be denied

Flint Water Crisis - Health Effects

  • Although the water source was changed back to Detroit’s Lake Huron system in Fall 2015 after lead was discovered, the damage was done. The number of children with elevated blood-lead levels (≥\geq5 micrograms per deciliter) nearly doubled in Flint after the water switch, Dr. Mona Hanna- Attisha, the director of the pediatric residency program at Flint's Hurley Medical Center, pointed out in September.

Flint Water Crisis - State of Emergency

  • JAN. 5: Snyder declares a state of emergency in Flint, the same day federal officials confirm that they are investigating.
  • JAN. 12: Snyder activates the Michigan National Guard to help distribute bottled water and filters in Flint and asks the federal government for help.
  • JAN. 13: Michigan health officials report an increase in Legionnaires' disease cases during periods over the past two years in the county that includes Flint.

Lead Mitigation

  • Until the service lines are replaced, under the circumstances of Flint it will be difficult to assure a mitigation of the lead problem
  • Flint has only served to highlight a lead problem in many older urban cities.
  • New Jersey, too, has only now begun to deal with the problem of lead in its major cities with old lines that may have lead constituents in the system.

Lead Care II

  • Blood lead Testing on-site

Physiologic Effects of Lead

  • No known threshold for effects of lead
  • Affects all organ systems
  • Developmental neurologic effects of greatest concern

Renal Effects of Lead

  • Acute exposure: reversible effects
  • Chronic exposure: nephropathy (chronic interstitial nephritis)
  • Childhood exposures → adult renal disease

Hematologic Effects of Lead

  • Interferes with production of hemoglobin
  • Can induce two kinds of anemia:
    • Acute exposure → hemolytic
    • Chronic exposure → synthetic
  • Threshold for adults: 50mcg/dL50 mcg/dL

Cardiovascular Effects of Lead

  • Increases risk of hypertension
  • Inverse correlation between BLLs and vitamin D levels
  • Chronic exposure may affect thyroid function

Endocrine Effects of Lead

Neurologic Effects of Lead

  • Neurologic effects on children documented at levels below 10mcg/dL10 mcg/dL
  • Low exposure effects: lowered IQ, attention deficits
  • High exposure effects: irritability, convulsions, coma, or death
  • Similar effects in adults at higher exposure levels

Developmental Effects of Lead

  • Crosses the placental barrier
  • Affects fetal viability, and fetal and early childhood development
  • Maternal lead may affect child’s neurologic development

Children's Exposure Pathways

  • Diet
  • Drinking water
  • Paint
  • Soil / Dust
    • Outdoor
    • Indoor
  • Air
  • Other sources

Children's Exposure Compared to Adults

  • Children Take in More Air, Water and Food Per Pound Than Adults
    • 2 times resting air intake
    • 3-4 times food intake
    • 3 times skin absorption
    • 3 times water intake

Lead - Biologic Fate

  • Lead in Environment (soil, air, water, food)
    • Ingestion -> Gastro Intes.
    • Inhalation -> Lung
    • Dermal -> Skin
    • Blood -> Storage -bone -fat -organs Liver -> Feces, Lung, Urine, Secretions

Childhood Lead Exposure - Biologic Fate

  • Childhood Lead Exposure (soil or dust or in this case water)
    • Ingestion -> Gastro Intes.
    • Blood -> Storage -bone -fat -organs Liver -> Feces, Urine

Biologic Fate

  • Most lead is excreted
  • Children and pregnant women absorb more lead than others
  • Exchanged between blood, soft tissues, and mineralizing tissues

Mitigating Lead Exposure

  • There are environmental actions that can help mitigate exposure such as proper nutrition and early childhood education. But that's made more difficult in a city with inadequate resources and without a grocery store.
  • "We need some money for infrastructure," said Weaver, new mayor of Flint Michigan who took office in the wake of the scandal. "We've got to get all of these kids and all of these families the services they deserve because of what's happened.
  • New Jersey lawmakers recently advanced a plan to identify and replace lead pipes lurking under homes and businesses in New Jersey, as well as measures to better track and identify the pipes that can be a threat to children.

Nickel

  • Classified as a heavy metal
  • One of the constituents of the earth’s crust
  • Human exposure to low levels likely universal and unavoidable
  • Uses of nickel
    • Production of many common appliances and tools (e.g., nickel cadmium batteries)

Effects of Nickel Exposure

  • Contact dermatitis (nickel allergy)
  • Cardiovascular-related and renal diseases
  • Fibrosis of the lungs
  • Potential carcinogenic action

Essential Metals with Potential for Toxicity

  • Toxic at high levels
    • Copper
    • Zinc
    • Iron
  • An optimal range of these essential metals is necessary to maintain health.

Copper and the Environment

  • Present in electrical wires, pipes, in combination with other metals to form alloys, as a mildew inhibitor, and as a wood and leather preservative
  • Approximately 1.4 billion pounds of copper were released into the environment during industrial processing in 2000 alone (per ATSDR estimates).

Exposure to Copper

  • Routes of exposure:
    • Inhalation
    • Ingestion of copper-containing foods and water
    • Direct contact with the skin
  • Tap water considerations
    • Small amounts may dissolve into tap water from copper piping, increasing copper levels

Effects of Copper Exposure

  • Concentrated amounts (far above trace levels):
    • Respiratory and gastrointestinal disturbances
  • Copper dust:
    • Irritation of the respiratory tract (e.g., nose and mouth)
  • Very high levels:
    • Liver and renal damage
    • Death

Zinc

  • Frequently occurring element found in the earth’s crust
  • Permeates air, soil, water, and, to some degree, all foods
  • Used commercially:
    • Coating for rust inhibition
    • Component of batteries
    • Alloys
  • Nutritional element important for maintaining health

Negative Effects of Excessive Amounts of Zinc

  • Gastrointestinal problems
    • Stomach cramps, nausea, and vomiting
  • Anemia
  • Damage to the pancreas
  • Metal fume fever (inhalation)
    • Appears to be an immune-mediated response that originates in the lungs

Iron

  • One of the most ubiquitous metals in the earth’s crust
  • Vital to human health
    • Growth of cells
    • Transport of oxygen within the circulatory system

Iron Toxicity

  • Acute iron intoxication (accidental iron poisoning)
    • Among most common childhood poisonings
  • Other groups at risk from iron overload (iron toxicity)
    • Adult men
    • Postmenopausal women
    • Often excess ingestion is through overdosing vitamin pills
  • The amount of iron ingested may give a clue to potential toxicity. The therapeutic dose for iron deficiency anemia is 3-6 mg/kg/day. Toxic effects begin to occur at doses above 20 mg/kg of elemental iron. Ingestions of more than 60 mg/kg of elemental iron are associated with severe toxicity. Often excess ingestion is through vitamins and syrups

Iron Requirements

  • Estimates of the minimum daily requirement for iron depend on age, sex, physiological status, and iron bioavailability and range from about 10 to 50 mg/day.
  • In drinking-water supplies, iron(II) salts are unstable and are precipitated as insoluble iron(III) hydroxide, which settles out as a rust-coloured silt. Anaerobic groundwaters may contain iron(II) at concentrations of up to several milligrams per litre without discoloration or turbidity in the water when directly pumped from a well, although turbidity and color may develop in piped systems at iron levels above 0.05–0.1 mg/litre. Staining of laundry and plumbing may occur at concentrations above 0.3 mg/litre.

Metals Used in Medical Therapies

  • Aluminum
  • Lithium
  • Platinum

Aluminum

  • Silver-white metal
  • Used widely in food and beverage containers, in pots and pans, and in construction sites
  • An ingredient in various medicines and cosmetics (e.g., to buffer aspirin and in antiperspirants)
  • Concern about possible association with Alzheimer’s disease