Kemisk Institut, Kbenhavn, 13 Dezember 2006Miljbelastning med anthropogene stoffer Eksempel bly: konsekvenser, iagttagelser og helbred Hans von Storch Institut fr Kstenforschung, GKSS Forschungszentrum
The case of Germany
Is it doable to estimate lead concentrations in the atmosphere and in human blood with a simple regression-type model?
What were the levels of lead concentration in human blood in Germany in the 196s and 1970s (a time for which no measurements are available)?
How can we design scenarios of lead levels in human blood conditional upon alternative political regulations?
Annual gasoline sales and lead emissions in Germany. Volume of gasoline sold (millions of liters per year; solid) and of leaded gas (after 1985; red crosses); amount of lead added to gasoline (in tons; yellow).
We have two data sets with time series of lead concentrations in human blood (LHB), beginning in the late 1970s. No reliable earlier data about lead in the human blood in Germany is available. Data set G (Germany; Heinzow, 1998) is unsystematically collected, with samples at different locations, different methods, different age and gender groups. The second data set M (Mnster; Human-Probenbank Mnster 2002;) is better, as it is derived from a controlled sampling strategy for groups of students living in the industrial town of Mnster (51.5oN, 7.4oE) in Nordrhine-Westfalia, close to the Ruhr area with heavy industry and intensive road traffic.
Data set G (Heinzow) and M (Mnster) with lead concentration in human blood (in g/l). The G data are split into adults and children.
Similarity of lead concentration in human blood sampled in the same year. Based on G and M data.
Lead concentration in gasoline and in blood in Germany. Heinzow (G) and Mnster (M) data sets. The lead concentration in 1985 to 1995 is an "effective" concentration for West Germany, by proportionally weighting the concentrations in of leaded (0.015 g/l) and unleaded (0.013 g/l) gasoline
Data set G: There is a linear relationship between the mean concentration and the dispersion of the sample distributions. standard deviation = 0.43 mean 3.9, (1)95% quantile = 1.63 mean + 10.9 (2)Scatter diagrams of sample means (horizontal axis) and sample standard deviations (dots, red) and 95% quantiles (diamonds, green) in lead concentrations in human blood in data set G. In g/l.
Data set G: According to (1), if the mean blood concentration is 150 g/l, then on average one sixth of the population will have more than 200 g/l or less than 100g/l. This rough estimate is based on the assumption of a normal distribution, which is not really valid as the distribution of lead levels is skewed, with a long tail towards large values
. Thus, it is more appropriate to use percentiles:If the mean concentration is 150g/l, then according to (2) 5% of the population may have a concentration of more than 250 g/l.
Critical Values of Lead Concentration in Human BloodCategory 1: unobstrusive valueCategory 2: no health risks are expected but monitoring is recommendedCategory 3: health hazards are possible, clarification and mitigation is neededSource: Krause et al. 1996Defined by the `Human-Biomonitoring-Kommission in Germany* women in child-bearing age
Scatter diagrams of sample means (horizontal axis) and sample 95% (diamonds) and 90% (dots) quantiles (vertical axis) in lead concentrations in human blood in data set M. In g/l.
In case of data set M, the 90% and 95% quantiles are given. Also in this case, a clear linear relationship between the mean and the quantiles is emerging with
90% quantile = 1.46 mean 2.2(3)95% quantile = 1.75 mean 4.6. (4)
According to (3) and (4), a mean concentration of 150g/l is associated with 5% (10%) of the population having more than 258 g/l (217 g/l) lead in their blood.
A simple dynamical relationship between three variables, namely the emission of lead LEt in an area AE in the year t, the atmospheric concentration LCt in an area AC in the year t and the mean concentration of lead in human blood LHBt in the year t in the area AC.
LCt+1 = LCt + LEt+1(5)LHBt+1 = LHBt + LCt+1 + (6)
Equation (6) is equivalent to(LHBt+1 - ) = (LHBt - ) + LCt+1 (7)
with = /(1-). Formulation (7) describes the dynamics of anomalies LHBt- relative to a normal state towards which the system converges as soon as the forcing LCt ceases if
Estimates of emitted lead in Germany in tons/year.Dots: Linearly interpolated estimates by Pacyna and Pacyna (2000). Crosses: Estimates based on volume of gasoline sold in West Germany, according to MWV (1998, 2002)
Best guess of lead emissions in the 6-grid box AE surrounding Mnster in tons/year. The times with an estimate from Pacyna is given by a big dot. The blue time series is used as input in the reconstruction 1955-1995 of lead concentrations in the air (5) and in the blood (7).
Equation 5/6LCt+1 = LCt + LEt+1LC = lead concentration in the atmosphereLE = total lead emissionLHB = lead concentration in human bloodLHBt+1 = LBHt + LCt+1 +
Lead concentration LCt in the air, in ng/m3, in the 50 50 km2 grid cell containing the town of Mnster as simulated in the reconstruction, and as estimated using the linear model (5) (red) Mnster emissions LEt.LCt+1 = LCt + LEt+1 (5)
Fit of equation (7) and test of equation (4) for data set M.. The upper two curves refer to the 95%-iles, and the lower two to the means. The estimated mean curve is derived by using simulated air concentrations in Mnster and the 1981 observed blood level as initial value; the curve for the estimated 95%-iles is obtained by using the estimated means and applying formula (4).(LHBt+1 - ) = (LHBt - ) + LCt+1 (7)95% quantile = 1.75 mean 4.6. (4)
Estimated mean, 90%ile and 95%ile lead concentrations in human blood in Mnster, according to (6/7) and (3/4 (red solid lines, M). Additionally the mean level estimated with the Germany model is given as dotted blue curve (G). A level of more than 150 g/l are considered in Germany as potentially harmful for children and women in child-bearing age (HBM 3). For other adults the limit for serious concern is set to 250 g/l.
Three scenarios of reduction of lead used as anti-knock in gasoline in Germany. The big black symbols describe the actual concentrations.
Scenarios for mean lead concentrations (g/l) in human blood, as derived by the Mnster model. Scenario 1 describes an evolution without regulation (i.e., ongoing use of 0.6 g/l lead in gasoline in Germany, upper curves). In scenario 2 no unleaded gasoline has been introduced in Germany in 1985 (middle curves), and in scenario 3, regulation was instituted in Germany already in 1961 (lower curves).
ConclusionsIt is possible to reconstruct atmospheric lead concentrations and blood lead levels using a simple regression model
It is possible to estimate lead concentrations in human blood using only lead emissions
Reducing the lead content in gasoline was a successful environmental policy to limit human health risks
Rest of the world
USAAfter Kitman, Nation 270, March 20, 2000
May 8, 2001New Warnings on Lead and ChildrenBy ERIC NAGOURNEYnew study raises questions about whether the current measure used to define lead poisoning is stringent enough.Lead poisoning has been redefined over the years, as doctors have decided that smaller and smaller amounts are acceptable. It is now considered to occur at 10 micrograms of lead per deciliter of blood.But researchers told a recent gathering of the Pediatric Academic Societies of evidence that even at levels lower than that, lead in the bloodstream appears dangerous.The primary researcher, Dr. Bruce Lanphear of the Children's Hospital Medical Center of Cincinnati, said that in the children he and his colleagues had studied, I.Q. declined in those with less than 10 micrograms of lead per deciliter of blood. The findings, he said, suggest that millions more children in the United States than previously suspected may be at risk."This is clearly a major public health crisis, and there really is too much complacency about this as a public health issue," he said.The researchers studied 276 children born in five hospitals in Rochester, N.Y., and then kept track of them for five years, measuring their lead levels and then their I.Q.'s at age 5.The researchers reported finding an inverse relationship between I.Q. and lead levels. Among all the children, they said, there was an average 5.5 percent reduction in I.Q. for every 10-microgram increase in lead.
Lead Use in Gasoline in 1996Source: modified from World Bank 1997
Country Western EuropeLead Content in Gasoline (g/l)Market Share of Leaded Gasoline (%)Austria00 (since 1993)Belgium0.01326Denmark00Finland00France0.01338Germany0.0133Greece 0.4 (0.15 in Athens)67 (since 1995)Iceland0.01315Ireland 0.01335Italy 0.01356Luxembourg 0.01318Netherlands 0.01314Norway 0.0132Portugal 0.461Spain 0.477Sweden 00 (since 1994)Switzerland 0.01313Turkey 0.482United Kingdom 0.01333
Country Central and Eastern EuropeLead Content in Gasoline (g/l)Market Share of Leaded Gasoline (%)Bulgaria0.1595Croatia 0.670Czech Republic 0.1545Hungary 0.1536Moldova 0.4100Poland 0.1530Romania 0.694Russian Federation 0.650Slovak Republic 00 (since 1995)
Thomas and Kwong, 2001
Source: World Bank (1997), Heinzow et al. (1998)Blood Lead Levels in Different Cities in 1980s and 1990sUS- scientists expect health dangers for children above a blood lead level of 100mg/l.German experts are convinced there