LDL stands for low density lipoprotein, known as "bad cholesterol". HDL stands for high density lipoprotein, known as "good cholesterol" (see further down for an explanation on cholesterol).
We are exposed to perfluoroalkyl acids through dust, food packaging, breast milk, microwave popcorn, air and occupational exposure, and drinking water, the authors explain.
Perfluoroalkyl acids are used in the manufacture of fluoropolymers, which give cookware their non-stick and heat-resistant qualities. Perfluoroalkyl acids are also used in fabrics and upholstery to make them waterproof.
According to recent national survey results, PFOA and PFOS hahaves been detected in virtually all samples of human serum.
When compounds used as coating for commercial food packaging, factory treatment for fabrics and carpets and manufacturer pre-treatment for stain resistant clothing break down, certain amounts of PFOA and PFOS are produced.
Perfluoroalkyl acid exposure primarily affects the liver, according to animal studies, with the potential effect in humans of raising LDL cholesterol levels.
Stephanie J. Frisbee, M.Sc., M.A., West Virginia University School of Medicine, Morgantown, and team examined the serum lipid levels of 12,476 children and teens included in the C8 Health Project, the result of a settlement of a class-action lawsuit regarding PFOA tainted drinking water in the mid-Ohio Valley.
After enrolling in 2005-2006, the participants (average age, 11.1 years) gave blood samples:
- Their average PFOA concentration was 69.2 nanograms per milliliter
- Their average PFOS concentration was 22.7 nanograms per milliliter
- Among 12- to 19-year old participants, PFOA concentrations were higher than those detected in a nationally representative survey (29.3 nanograms per milliliter vs. 3.9 nanograms per milliliter)
- PFOS concentrations were similar (19.1 nanograms per milliliter vs. 19.3 nanograms per milliliter)
The researchers found that (on average) the 20% of the children and adolescents with the top PFOA levels had total cholesterol levels 4.6 milligrams per deciliter higher and and LDL cholesterol levels 3.8 milligrams per deciliter higher than the 20% with the lowest PFOA levels.
Additionally, the researchers detected an average difference of 8.5 milligrams per deciliter in total cholesterol levels and 5.8 milligrams per deciliter in LDL cholesterol levels between the one-fifth of participants with the highest and lowest PFOS levels.
The authors wrote:
The non-linear nature of the observed associations, particularly for PFOA, suggests a possible saturation point in an underlying physiologic mechanism. PFOA and PFOS specifically, and possibly perfluoroalkyl acids as a general class, appear to be associated with serum lipids, and the association seems to exist at levels of PFOA and PFOS exposure that are in the range characterized by nationally representative studies.
Because of the design of the study, the cause-and-effect interpretations are limited, the authors stressed. Even so, the results suggest that the link between PFOA and PFOS and higher cholesterol levels warrants further study.
Should the association prove to be etiologic, the cumulative effects of such an elevation in cholesterol on long-term cardiovascular health are unclear given the early age at which these associations were observed.
What is cholesterol?Cholesterol is a lipid (fat) which is produced by the liver and is vital for normal body functioning. Cholesterol exists in the outer layer of every cell in our body and has several functions. It is a waxy steroid and is transported in the blood plasma of all animals. It is the main sterol synthesized by animals - small amounts are also synthesized in plants and fungi.
Cholesterol is carried in the blood by molecules called lipoproteins. A lipoprotein is any complex or compound containing both lipid (fat) and protein. The three main types are:
- LDL (low density lipoprotein) - people often refer to it as bad cholesterol. LDL carries cholesterol from the liver to cells. If too much is carried, too much for the cells to use, there can be a harmful buildup of LDL. This lipoprotein can increase the risk of arterial disease if levels rise too high. Most human blood contains approximately 70% LDL - this may vary, depending on the person.
- HDL (high density lipoprotein) - people often refer to it as good cholesterol. Experts say HDL prevents arterial disease. HDL does the opposite of LDL - HDL takes the cholesterol away from the cells and back to the liver. In the liver it is either broken down or expelled from the body as waste.
- Triglycerides - these are the chemical forms in which most fat exists in the body, as well as in food. They are present in blood plasma. Triglycerides, in association with cholesterol, form the plasma lipids (blood fat). Triglycerides in plasma originate either from fats in our food, or are made in the body from other energy sources, such as carbohydrates. Calories we consume but are not used immediately by our tissues are converted into triglycerides and stored in fat cells. When your body needs energy and there is no food as an energy source, triglycerides will be released from fat cells and used as energy - hormones control this process.
The amount of cholesterol in human blood can vary from 3.6 mmol/liter to 7.8 mmol/liter. The National Health Service (NHS), UK, says that any reading over 6 mmol/liter is high, and will significantly raise the risk of arterial disease. The UK Department of Health recommends a target cholesterol level of under 5 mmo/liter. Unfortunately, two-thirds of all UK adults have a total cholesterol level of at least five (average men 5.5, average women 5.6).
The dangers of high cholesterol High cholesterol levels can cause:
- Atherosclerosis - narrowing of the arteries.
- Higher coronary heart disease risk - an abnormality of the arteries that supply blood and oxygen to the heart.
- Heart attack - occurs when the supply of blood and oxygen to an area of heart muscle is blocked, usually by a clot in a coronary artery. This causes your heart muscle to die.
- Angina - chest pain or discomfort that occurs when your heart muscle does not get enough blood.
- Other cardiovascular conditions - diseases of the heart and blood vessels.
- Stroke and mini-stroke - occurs when a blood clot blocks an artery or vein, interrupting the flow to an area of the brain. Can also occur when a blood vessel breaks. Brain cells begin to die.
Results From the C8 Health Project
Stephanie J. Frisbee, MSc, MA; Anoop Shankar, MD, PhD; Sarah S. Knox, PhD; Kyle Steenland, PhD; David A. Savitz, PhD; Tony Fletcher, PhD; Alan M. Ducatman, MD, MS
Arch Pediatr Adolesc Med. 2010;164(9):860-869. doi:10.1001/archpediatrics.2010.163