What are the critical blood concentration levels for PCBs?

Definition of a PCB blood toxicity threshold

PCB toxicity is not directly related to the quantity consumed at a given time but mainly to its accumulation in the body. ANSES reviewed the existing scientific data to determine the thresholds below which health risks are regarded as negligible. These thresholds are called “critical blood concentration levels”.

Why study PCB levels in the body?

Exposure to PCBs in humans occurs mainly through food consumption. The Agency’s 2007 assessment of food-related exposure to PCBs in the French population showed that in the most highly exposed populations, mainly children and adults who consumed large amounts of fish, the tolerable daily intake (TDI) – amount of PCB to which an individual may be exposed daily over a lifetime, without any risk to health – was exceeded.

However, the level of toxicity of PCBs is not directly related to the quantity consumed at a given time (periodic exposure to PCBs through eating a single highly contaminated food has little impact on health) but is essentially dependent on the amount accumulated in the blood and fatty tissues over time (the concentration level in the body). PCBs can accumulate in the body’s fatty tissues and may then be found in high levels in mother’s milk and blood-lipid fractions. Since evaluating the quantity of PCB to which the population is exposed daily is insufficient for risk assessment, it is thus necessary to know the quantity of PCBs stored in the body, i.e., the body burden. To do this, the presence of PCB in the blood is measured because it reflects the overall body burden.

What impact can chronic exposure to PCBs have on health?

The impact of PCBs on human health has been examined in various epidemiological studies conducted in the United States, Canada and Europe, respectively.

In 2007, the Quebec National Institute for Public Health (INSPQ) provided a critical overview of all the studies published since 1997 in order to analyse the causal relationship between exposure to PCBs and the onset of health problems in exposed individuals.

In Europe, the impact on health of chronic exposure to low doses of PCBs has also been demonstrated through analysis of the results of the PCBRISK project, an epidemiological study. This study, conducted in a historically polluted region of Eastern Slovakia, is the most exhaustive European epidemiological study in terms of levels of exposure and PCB blood concentration.

To date, the effects on health linked to exposure to PCBs that are most commonly reported in humans are:

  • effects on mental and motor development, and disturbances in immune mechanisms in children exposed in utero or during the perinatal period through breastfeeding and up to age three;
  • effects on the endocrine system (especially the thyroid) in the rest of the population.

Other effects have sometimes been reported with no clearly established causal relationship with chronic exposure to PCBs. This particularly applies to impaired fertility in men, metabolic disturbances (glucose metabolism in particular) and adult neurological disorders.

What does “critical concentration level” mean?

Critical concentration levels are the body burden levels of PCBs below which the probability of effects on health is regarded as negligible.

They serve as benchmarks:

  • to place in context the blood PCB levels observed in populations;
  • to guide public policy for protecting the general population and vulnerable populations in particular (women of childbearing age, breastfeeding women, children under three years of age and regular consumers of highly contaminated foods related to a local emission source, for example).

To date, critical concentration levels reported in the international literature for women of childbearing age, breastfeeding women, and children under three years of age vary between 700 and 1000 ng of total PCB per gram of maternal plasma lipids. They were established based on effects observed in children exposed during the perinatal period.

What is the Agency’s position?

In the current state of knowledge, the Agency considers that the effects of PCBs on the mental and motor development of children exposed in utero are the best documented “critical effects” for establishing the critical concentration level in humans, and therefore recommends setting the critical concentration threshold for pregnant women, women of childbearing age, breastfeeding women and children under three years of age at 700 ng of total PCB per gram of plasma lipids.

Due to the persistent nature of PCBs in the body and the associated gradual rise in concentration levels with age, the Agency also recommends applying this threshold level to young and teenage girls.

In boys over three years of age, adult men and women beyond childbearing age, the Agency considers that the available data are fragmentary and even contradictory and therefore difficult to interpret on a clinical level.

Nevertheless, the Agency recommends setting the critical concentration level for the rest of the population at 1800 ng of total PCB per gram of plasma lipids.

The average concentration of total PCBs in the French general population is 480 ng per gram of lipids [French Nutrition and Health Survey (ENNS) conducted by the French Institute for Public Health Surveillance (InVS), 2011].