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