The silent peril of forever chemicals

PFAS, tox­ic and per­sist­ent chem­ic­al com­pounds, have invaded every corner of our plan­et. While the bio­lo­gic­al sci­ence com­munity is mobil­ising to seek out micro-organ­isms poten­tially cap­able of degrad­ing them, the solu­tion goes bey­ond the labor­at­ory, call­ing for a col­lect­ive and reg­u­lat­ory response.

Alarm­ing fig­ures testi­fy to the scale of the pol­lu­tion: 1,433 ng/L at the bot­tom of a well in the Béarn vil­lage of Monts, 1,546 ng/L at the out­let of a bore­hole in La Tremblade oppos­ite the Ile d’Oléron, 2,399 ng/Kg in hens’ eggs near the indus­tri­al basin of Pierre-Bén­ite south of Lyon. These read­ings are among the French sites most con­tam­in­ated by PFASs, so-called “forever chem­ic­als” that are of con­cern to the sci­entif­ic com­munity and bey­ond, because of their tox­icity and per­sist­ence in the environment.

The acronym PFAS stands for per- and poly-fluoroal­kylated sub­stances. “These indus­tri­al chem­ic­al com­pounds are used in many every­day products, such as food pack­aging plastics and bat­ter­ies,” explains Stéphane Vuil­leu­mi­er, micro­bi­o­lo­gist and pro­fess­or at the Uni­ver­sity of Stras­bourg. They are also found in fire-fight­ing foams, paper pro­duc­tion pro­cesses and tex­tile finishing.

In early 2023, a con­sor­ti­um of major European media, includ­ing Le Monde and The Guard­i­an, car­ried out an impress­ive invest­ig­a­tion that pro­duced a detailed map¹ of PFAS-con­tam­in­ated sites across the con­tin­ent. Their work sheds light on the massive pol­lu­tion of European water, sed­i­ment and soil. They lis­ted tens of thou­sands of sites, includ­ing just over 2,100 « hot spots », where con­cen­tra­tions far exceed the thresholds deemed dan­ger­ous to health (i.e. 100 ng/L).

How­ever, this map­ping only lists sites that have been tested or iden­ti­fied as being par­tic­u­larly exposed, and only includes the best-known sub­stances (around ten). How­ever, the research­er points to the pub­lic­a­tion of a new nomen­clature that now clas­si­fies sev­er­al mil­lion dif­fer­ent sub­stances² in this cat­egory, sug­gest­ing that the spread of PFAS is gen­er­ally under­es­tim­ated. “There isn’t a single place on Earth that does­n’t have traces of PFAS,” insists the researcher.

Des­pite the sci­entif­ic evid­ence of their harm­ful­ness “even at very low con­cen­tra­tions”, these sub­stances con­tin­ue to be widely pro­duced and used by man­u­fac­tur­ers, who have no sat­is­fact­ory altern­at­ives. Stéphane Vuil­leu­mi­er points out that their dele­ter­i­ous effects on human health are becom­ing increas­ingly well doc­u­mented, “par­tic­u­larly on the immune sys­tem³ and on hor­mones, by act­ing as endo­crine dis­ruptors⁴”.

PFAS are described as forever chem­ic­als, because they have the par­tic­u­lar­ity of being made up of a car­bon-flu­or­ine bond that makes it impossible for them to bio­de­grade. “There are very few nat­ur­al organ­ic com­pounds that con­tain flu­or­ine,” explains Michael Ryck­elyn­ck, a bio­chem­ist and pro­fess­or at the Uni­ver­sity of Stras­bourg. In 2020, this spe­cial­ist in micro­fluidics teamed up with Stéphane Vuil­leu­mi­er to find bac­teria cap­able of break­ing this bond, of deflu­or­in­at­ing. The prob­lem? It is estim­ated that over a bil­lion dif­fer­ent spe­cies of bac­teria exist today. Find­ing the ideal can­did­ate is like look­ing for a needle in a haystack.

“Our expert­ise in micro­fluidics enables us to speed up tests and reac­tions by mini­atur­ising them into pico­litre volumes,” he explains. With this scale of exper­i­ment, research­ers can ana­lyse a very large quant­ity of samples in a single step. “Rather than pre-select­ing can­did­ate enzymes and bac­teria and then test­ing them one by one, we are look­ing for the deflu­or­in­a­tion func­tion in a large sample (…), at a rate of two mil­lion ana­lyses per hour.” They have cre­ated an “ana­lys­is pipeline” in which the can­did­ate bac­teria inter­act with PFAS and a flu­or­ide detect­or. If one of these bac­teria is cap­able of degrad­ing the com­pound, a flu­or­ide ion is released. This will be detec­ted by fluor­es­cence, enabling the research­ers to identi­fy the bac­teria respons­ible and isol­ate it for fur­ther study.

Their ini­tial work⁵ demon­strated the effect­ive­ness of the deflu­or­id­a­tion detect­or. They are now focus­ing on ana­lys­ing envir­on­ment­al samples (prefer­ably from con­tam­in­ated sites) and improv­ing the degrad­a­tion prop­er­ties of some of the bac­teria of interest. The entire glob­al sci­entif­ic com­munity is pur­su­ing the same object­ive: to find the anti-PFAS bac­teri­um. How­ever, no single tech­no­logy will be enough to solve the prob­lem of PFAS. “A col­lab­or­at­ive approach to the sub­ject is essen­tial if we are to suc­ceed. We need to com­bine our detec­tion meth­od with innov­a­tions from oth­er labor­at­or­ies,” argues Michael Ryck­elyn­ck, “such as adsorp­tion mem­branes⁶ [edit­or­’s note: for cap­tur­ing and stor­ing PFAS], or oth­er phys­ic­al chem­istry approaches for degrad­ing these compounds.

The eco­nom­ic stakes for industry are titanic

This inter­dis­cip­lin­ar­ity has recently taken form in France with the ini­ti­at­ive of the Mis­sion pour les Ini­ti­at­ives Trans­verses et Inter­dis­cip­lin­aires of the CNRS, with a work­ing group⁷ ded­ic­ated to the detec­tion and decon­tam­in­a­tion of PFAS, as well as to altern­at­ives to these com­pounds. Chem­ists, phys­i­cists, bio­lo­gists, engin­eers, soci­olo­gists, math­em­aticians, and oth­ers are expec­ted to join this hot­bed of sci­ence, which will aim to accel­er­ate innov­a­tion and the emer­gence of con­crete solu­tions to deal with the prob­lem of PFAS in the best pos­sible way.

A sym­posi­um will be organ­ised in March 2024 to bring togeth­er this wide range of dis­cip­lines and to cre­ate inter­ac­tion with industry. “Industry must to be part of the equa­tion,” insists Stéphane Vuil­leu­mi­er. We need to build a rela­tion­ship of trust with them. Industry is a key gate­way for sci­ent­ists to access soil, sed­i­ment and water samples for ana­lys­is and treat­ment. They also have an interest in fol­low­ing sci­entif­ic advances closely, so that they can eval­u­ate pos­sible altern­at­ives to these sub­stances or imple­ment pol­lu­tion con­trol prototypes.

How­ever, the trend is not yet towards a reduc­tion in use, stresses the research­er, “because the eco­nom­ic stakes for industry are titan­ic”. PFAS are at the heart of the glob­al pro­duc­tion machine: “accel­er­a­tion in the man­u­fac­ture of bat­ter­ies for elec­tric vehicles, for example, which requires this type of sub­stance, will not neces­sar­ily facil­it­ate the emer­gence of solu­tions”. How­ever, the poten­tial future dis­cov­ery of “depol­lut­ing bac­teria” must not become a pre­text for con­tinu­ing to pol­lute. For the research­ers, we need to ask ourselves the right ques­tion: are we ready to do without PFASs? They are there­fore call­ing for changes in reg­u­la­tions to facil­it­ate the trans­ition pro­cess. “Decision-makers need to carry out a benefit/risk bal­ance between the fin­an­cial impact of restrict­ing the use of PFASs and the cost in terms of pub­lic health of their con­tin­ued release into the environment.”

Whatever the out­come, the sci­entif­ic com­munity is on the move, both to innov­ate in terms of pol­lu­tion con­trol solu­tions, and to inform pub­lic decision-mak­ing and curb the threat­en­ing dis­per­sion of these etern­al pollutants.

Samuel Belaud