EEA info graphic

The EEA just twittered that “Across EEA-33 countries, emissions of lead have decreased by 89%, mercury by 66% & cadmium by 64% from 1990 to 2011.”

What else to say than a big THANKS to those initiatives, organizations, interest groups, green lobbies and whoever else out there was putting effort into making these reductions come true?

Well – one thing to say is that there are still 1/10th of lead emissions to go, 1/3 of both mercury and cadmium. So keep it up! And thanks to the EEA for helping to regulate these heavy metals out of our lifes.

For all those interested in knowing why we don’t want these heavy metals in our lifes, here are some points that, not surprisingly, have been known for quite a long time.I copy freely from this 1987 book chapter by Hutton, entitled “Human Health Concerns of Lead, Mercury, Cadmium and Arsenic”.

The three metals, lead, mercury and cadmium, and the metalloid arsenic have all caused major human health problems in various parts of the world. The overt toxicity of these elements has been recognized for many years; indeed, the harmful effects of lead were known as far back as the second century BC in ancient Greece (Waldron, 1973).

In cases of high exposure, clinical signs and symptoms can be observed. At lower exposure levels clin- ical manifestations may be absent but effects may be observed at the physi- ological or biochemical level.

The US Environmental Protection Agency gives a short, non-exhaustive list of the effects of lead on humans:

  • damage to the brain and nervous system
  • behavioral problems
  • anemia
  • liver and kidney damage
  • hearing loss
  • hyperactivity
  • developmental delays
  • in extreme cases, death
  • nerve damage to the sense organs and nerves controlling the body
  • increased blood pressure
  • hearing and vision impairment
  • reproductive problems (e.g., decreased sperm count)
  • retarded fetal development even at relatively low exposure levels
  • persistent fatigue
  • irritability
  • loss of appetite
  • stomach discomfort and/or constipation
  • reduced attention span
  • insomnia

The US EPA gives a non-exhaustive list of the effects of mercury on humans:

  • Hand tremor
  • increases in memory disturbance
  • slight subjective and objective evidence of autonomic dysfunction
  • Autoimmune effects
  • Developmental neuropsychological impairment

And, finally, the US EPA information on cadmium‘s effect on humans:

  • Acute inhalation exposure to high levels of cadmium in humans may result in effects on the lung, such as bronchial and pulmonary irritation. A single acute exposure to high levels of cadmium can result in long-lasting impairment of lung function. (1,3,4)
  • Cadmium is considered to have high acute toxicity, based on short-term animal tests in rats. (5)
  • Chronic inhalation and oral exposure of humans to cadmium results in a build-up of cadmium in the kidneys that can cause kidney disease, including proteinuria, a decrease in glomerular filtration rate, and an increased frequency of kidney stone formation. (1,3,4)
  • Other effects noted in occupational settings from chronic exposure of humans to cadmium in air are effects on the lung, including bronchiolitis and emphysema. (1,3,4)
  • Chronic inhalation or oral exposure of animals to cadmium results in effects on the kidney, liver, lung, bone, immune system, blood, and nervous system. (1,3)
  • The Reference Dose (RfD) for cadmium in drinking water is 0.0005 milligrams per kilogram per day (mg/kg/d) and the RfD for dietary exposure to cadmium is 0.001 mg/kg/d; both are based on significant proteinuria in humans. The RfD is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily oral exposure to the human population (including sensitive subgroups) that is likely to be without appreciable risk of deleterious noncancer effects during a lifetime.  It is not a direct estimator of risk, but rather a reference point to gauge the potential effects.  At exposures increasingly greater than the RfD, the potential for adverse health effects increases.  Lifetime exposure above the RfD does not imply that an adverse health effect would necessarily occur. (6)
  • EPA has high confidence in both RfDs based primarily on a strong database for cadmium toxicity in humans and animals that also permits calculation of pharmacokinetic parameters of cadmium absorption, distribution, metabolism, and elimination. (6)
  • EPA has not established a Reference Concentration (RfC) for cadmium. (6)
  • The California Environmental Protection Agency (CalEPA) has established a chronic reference exposure level of 0.00001 milligrams per cubic meter (mg/m3) for cadmium based on kidney and respiratory effects in humans. The CalEPA reference exposure level is a concentration at or below which adverse health effects are not likely to occur. (7)
  • Limited evidence exists for an association between inhalation exposure and a reduction in sperm number and viability in humans. (1)
  • Human developmental studies on cadmium are limited, although there is some evidence to suggest that maternal cadmium exposure may result in decreased birthweights. (1)
  • Animal studies provide evidence that cadmium has developmental effects, such as low fetal weight, skeletal malformations, interference with fetal metabolism, and impaired neurological development, via inhalation and oral exposure. (1,3,4)
  • Limited animal data are available, although some reproductive effects, such as decreased reproduction and testicular damage, have been noted following oral exposures. (1)
  • Several occupational studies have reported an excess risk of lung cancer in humans from exposure to inhaled cadmium. However, the evidence is limited rather than conclusive due to confounding factors. (1,3,6)
  • Animal studies have reported cancer resulting from inhalation exposure to several forms of cadmium, while animal ingestion studies have not demonstrated cancer resulting from exposure to cadmium compounds. (1,3,6)
  • EPA considers cadmium to be a probable human carcinogen (cancer-causing agent) and has classified it as a Group B1 carcinogen. (6)
  • EPA uses mathematical models, based on animal studies, to estimate the probability of a person developing cancer from breathing air containing a specified concentration of a chemical. EPA calculated an inhalation unit risk estimate of 1.8 × 10-3(µg/m3)-1. EPA estimates that, if an individual were to continuously breathe air containing cadmium at an average of 0.0006 µg/m3 (6 x 10-7 mg/m3) over his or her entire lifetime, that person would theoretically have no more than a one-in-a-million increased chance of developing cancer as a direct result of breathing air containing this chemical. Similarly, EPA estimates that continuously breathing air containing 0.006 µg/m3 (6 x 10-6 mg/m3) would result in not greater than a one-in-a-hundred thousand increased chance of developing cancer, and air containing 0.06 µg/m3 (6 x 10-5 mg/m3) would result in not greater than a one-in-ten thousand increased chance of developing cancer. For a detailed discussion of confidence in the potency estimates, please see IRIS. (6)

This links to my point from yesterday, that yes we have good scientific knowledge of many processes, but a certain lack of interest to thoroughly follow up on them. E.g. with all the knowledge about the dangers of these heavy metals, it seems still surprising that it took soooooo unbelievable long to regulate down these heavy metals to only 1/3 of the 1990 levels, especially given that we already knew so well before 1990 that these pollutants are so dangerous!