Perfluorononanoic acid, or PFNA, is a synthetic

perfluorinated carboxylic acid Perfluoroalkyl carboxylic acids (PFCAs), or perfluorocarboxylic acids are compounds of the formula CnF(2n+1)CO2H that belong to the class of per- and polyfluoroalkyl substances. The simplest example is trifluoroacetic acid. These compounds are o ...

and

fluorosurfactant Per- and polyfluoroalkyl substances (PFASs) are synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain. An early definition, from 2011, required that they contain at least one perfluoroalkyl mo ...

that is also an environmental contaminant found in people and wildlife along with PFOS and

PFOA Perfluorooctanoic acid (PFOA; conjugate base perfluorooctanoate; also known colloquially as C8, for its 8 carbon chain structure) is a perfluorinated carboxylic acid produced and used worldwide as an industrial surfactant in chemical processes a ...

Chemistry and properties

In acidic form it is a highly reactive strong acid. In its

conjugate base A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a ...

form as a

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

it is stable and commonly ion paired with ammonium. In the commercial product Surflon S-111 (CAS 72968-3-88) it is the primary compound present by weight. PFNA is used as surfactant for the production of the fluoropolymer

polyvinylidene fluoride Polyvinylidene fluoride or polyvinylidene difluoride (PVDF) is a highly non-reactive thermoplastic fluoropolymer produced by the polymerization of vinylidene difluoride. PVDF is a specialty plastic used in applications requiring the highest pur ...

.Supporting Information
(PDF). It is produced mainly in Japan by the

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

of a linear

fluorotelomer Fluorotelomers are fluorocarbon-based oligomers, or telomers, synthesized by telomerization. Some fluorotelomers and fluorotelomer-based compounds are a source of environmentally persistent perfluorinated carboxylic acids such as PFOA and PFNA, w ...

olefin mixture containing F(CF₂)₈CH=CH₂. It can also be synthesized by the

carboxylation Carboxylation is a chemical reaction in which a carboxylic acid is produced by treating a substrate with carbon dioxide. The opposite reaction is decarboxylation. In chemistry, the term carbonation is sometimes used synonymously with carboxylatio ...

of F(CF₂)₈I. PFNA can form from the

biodegradation Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegrada ...

of 8:2 fluorotelomer alcohol. Additionally, it is considered a probable degradation product of many other compounds. PFNA is the largest perfluorinated carboxylic acid surfactant. Fluorocarbon derivatives with terminal

carboxylate In organic chemistry, a carboxylate is the conjugate base of a carboxylic acid, (or ). It is an ion with negative charge. Carboxylate salts are salts that have the general formula , where M is a metal and ''n'' is 1, 2,...; ''carboxylat ...

s are only surfactants when they possess five to nine carbons. Fluorosurfactants reduce the surface tension of water down to half of what

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...

surfactants can by concentrating at the liquid-air interface due to the

lipophobicity Lipophobicity, also sometimes called lipophobia (from the Greek λιποφοβία from λίπος ''lipos'' "fat" and φόβος ''phobos'' "fear"), is a chemical property of chemical compounds which means " fat rejection", literally "fear of fat ...

of fluorocarbons. PFNA is very stable and is not known to degrade in the environment by oxidative processes because of the strength of the

carbon–fluorine bond The carbon–fluorine bond is a polar covalent bond between carbon and fluorine that is a component of all organofluorine compounds. It is one of the strongest single bonds in chemistry (after the B–F single bond, Si–F single bond, and H–F ...

and the

electronegativity Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the ...

of fluorine.

Environmental and health concerns

Like the eight-carbon

, the nine-carbon PFNA is a developmental toxicant and an

immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splint ...

toxicant. However, longer chain

s (PFCAs) are considered more

bioaccumulative Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance at a rate faster than that at which the substance is lost or eliminated ...

and

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...

. PFNA is an agonist of the

nuclear receptors In the field of molecular biology, nuclear receptors are a class of proteins responsible for sensing steroids, thyroid hormones, vitamins, and certain other molecules. These receptors work with other proteins to regulate the expression of specif ...

PPARα Peroxisome proliferator-activated receptor alpha (PPAR-α), also known as NR1C1 (nuclear receptor subfamily 1, group C, member 1), is a nuclear receptor protein functioning as a transcription factor that in humans is encoded by the ''PPARA'' gen ...

and PPARγ. In the years between 1999–2000 and 2003–2004, the geometric mean of PFNA increased from 0.5

parts per billion In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they ...

to 1.0 parts per billion in the US population's blood serum. and has also been found in human follicular fluid In a

cross-sectional study In medical research, social science, and biology, a cross-sectional study (also known as a cross-sectional analysis, transverse study, prevalence study) is a type of observational study that analyzes data from a population, or a representative su ...

of 2003–2004 US samples, a higher (13.9

milligram The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially. ...

per

deciliter The litre (international spelling) or liter (American English spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3) ...

) total cholesterol level was observed in when the highest quartile was compared to the lowest. Non-

HDL cholesterol High-density lipoprotein (HDL) is one of the five major groups of lipoproteins. Lipoproteins are complex particles composed of multiple proteins which transport all fat molecules (lipids) around the body within the water outside cells. They are t ...

(or " bad cholesterol") levels were also higher in samples with more PFNA. In

bottlenose dolphins Bottlenose dolphins are aquatic mammals in the genus ''Tursiops.'' They are common, cosmopolitan members of the family Delphinidae, the family of oceanic dolphins. Molecular studies show the genus definitively contains two species: the comm ...

from

Delaware Bay Delaware Bay is the estuary outlet of the Delaware River on the northeast seaboard of the United States. It is approximately in area, the bay's freshwater mixes for many miles with the saltwater of the Atlantic Ocean. The bay is bordered inland ...

, PFNA was the perfluorinated carboxylic acid measured in the highest concentration in

blood plasma Blood plasma is a light amber-colored liquid component of blood in which blood cells are absent, but contains proteins and other constituents of whole blood in suspension. It makes up about 55% of the body's total blood volume. It is the intr ...

; it was found in concentrations well over 100 parts per billion. PFNA has been detected in

polar bears The polar bear (''Ursus maritimus'') is a hypercarnivorous bear whose native range lies largely within the Arctic Circle, encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the largest extant bear specie ...

in concentrations over 400 parts per billion. PFNA was the perfluorinated chemical measured in the highest concentration in Russian

Baikal seal The Baikal seal, Lake Baikal seal or (''Pusa sibirica''), is a species of earless seal endemic to Lake Baikal in Siberia, Russia. Like the Caspian seal, it is related to the Arctic ringed seal. The Baikal seal is one of the smallest true seal ...

s. However, PFOS is the

perfluorinated compound A perfluorinated compound (PFC) or perfluoro compound is an organofluorine compound containing only carbon-fluorines and C−C bonds, as well as potentially heteroatoms. Perfluorinated compounds have properties that result from the presence of flu ...

that dominates in most wildlife

biomonitoring In analytical chemistry, biomonitoring is the measurement of the body burden of toxic chemical compounds, elements, or their metabolites, in biological substances. Often, these measurements are done in blood and urine. Biomonitoring is performed ...

samples.Supporting Information
(PDF).

Drinking water regulations

In the United States there are no federal drinking water standards for any of the

perfluorinated alkylated substances Per- and polyfluoroalkyl substances (PFASs) are synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain. An early definition, from 2011, required that they contain at least one perfluoroalkyl m ...

as of late 2020. The

U.S. Environmental Protection Agency The Environmental Protection Agency (EPA) is an Independent agencies of the United States government, independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon pro ...

(EPA) published a non-enforceable health advisory for PFOA in 2016. The agency's health advisory level for the combined concentrations of PFOA and PFOS is 70 parts per trillion (ppt). In June 2020 the State of New Jersey published a drinking water standard for PFOA, the first state to do so. Public water systems in New Jersey are required to meet a maximum contaminant level (MCL) standard of 14 ppt. The state also set a PFOS standard at 13 ppt. The state had set a standard for PFNA in September 2018, with an MCL of 13 ppt. In August 2020 the

State of Michigan Michigan () is a state in the Great Lakes region of the upper Midwestern United States. With a population of nearly 10.12 million and an area of nearly , Michigan is the 10th-largest state by population, the 11th-largest by area, and the ...

adopted drinking water standards for 5 previously unregulated PFAS compounds and lowered acceptable levels for 2 previously regulated compounds PFOS and PFOA to 16 ppt and 8 ppt respectively. PFNA has a MCL of 6 ppt.

Food Regulation

In 2020, the

European Food Safety Authority The European Food Safety Authority (EFSA) is the agency of the European Union (EU) that provides independent scientific advice and communicates on existing and emerging risks associated with the food chain. EFSA was established in February 2002, ...

added PFNA in its revised safety threshold for PFAS that accumulate in the body. They set the threshold for a group of four PFAS of a tolerable weekly intake of 4.4 nanograms per kilogram of body weight per week.

Product Restrictions

In 2020, a California bill was passed banning PFNA as an intentionally added ingredient from cosmetics.

References

External links

Perfluorocarboxylic Acid Content in 116 Articles of CommercePDFCenters for Disease Control and Prevention, Polyfluorochemicals fact sheetPerfluorinated substances and their uses in SwedenPerfluoroalkylated substances, Aquatic environmental assessmentChain of Contamination: The Food Link, Perfluorinated Chemicals (PFCs) Incl. PFOS & PFOA
{{PPAR modulators Perfluorocarboxylic acids PBT substances Anionic surfactants