How safe sub­stances be­come dan­ger­ous

Financial Mirror (Cyprus) - - FRONT PAGE -

Since the de­vel­op­ment of the science of tox­i­col­ogy in the 16th cen­tury, its guid­ing prin­ci­ple has been that “the dose makes the poi­son.” It is a rule that ap­plies to the medicines used by pa­tients world­wide many bil­lions of times a day. The right dose of aspirin can be a ther­a­peu­tic god­send, but con­sum­ing too much can be lethal. The prin­ci­ple even ap­plies to foods: large amounts of nut­meg or licorice are no­to­ri­ously toxic.

The risk that a sub­stance poses broadly de­pends on two fac­tors: its in­her­ent ca­pac­ity to cause harm and one’s ex­po­sure to it. It is a sim­ple idea, but even some pre­sump­tive pro­fes­sion­als seem un­able to grasp it – as ev­i­denced by the de­ci­sion by the In­ter­na­tional Agency for Re­search on Can­cer (IARC), a com­po­nent of the World Health Or­gan­i­sa­tion, to clas­sify the com­monly used her­bi­cide 2,4-D as “pos­si­bly car­cino­genic to hu­mans.”

When it comes to her­bi­cides, the IARC seems to be on a los­ing streak. The or­gan­i­sa­tion re­cently clas­si­fied glyphosate, another pop­u­lar her­bi­cide, as “prob­a­bly” car­cino­genic, a con­clu­sion at odds with those of reg­u­la­tory agen­cies around the world.

Sim­i­larly, not a sin­gle gov­ern­men­tal agency has deemed 2,4-D a car­cino­gen. Ear­lier this year, the United States En­vi­ron­men­tal Pro­tec­tion Agency (EPA) con­cluded that “based on weight of ev­i­dence con­sid­er­a­tion of the avail­able data, 2,4-D would be clas­si­fied as ‘Not Likely to be Car­cino­genic to Hu­mans.’” The Euro­pean Food Safety Au­thor­ity also re­cently con­cluded that “2,4-D, as cur­rently man­u­fac­tured, is un­likely to have a geno­toxic po­ten­tial or pose a car­cino­genic risk to hu­mans.”

The de­ci­sion by the IARC to clas­sify sub­stances like 2,4-D and glyphosate as po­ten­tially harm­ful is likely to cause alarm among farm­ers and con­sumers, who will won­der about the ap­pro­pri­ate­ness of its con­tin­ued use in com­mer­cial agri­cul­ture or gar­den­ing. This would be a shame, be­cause these are highly ef­fec­tive and widely used her­bi­cides, and when the IARC makes its de­ci­sions, it does not con­sider whether the sub­stance in ques­tion is ac­tu­ally likely to cause can­cer in the real world. Its pan­els do not as­sess whether a chem­i­cal will cause can­cer – only if it is ca­pa­ble of caus­ing can­cer.

As a re­sult, the IARC has in the past clas­si­fied aloe vera, acryl­amide (a sub­stance cre­ated by fry­ing foods, such as French fries and potato chips), cell phones, work­ing night shifts, Asian pick­led veg­eta­bles, and cof­fee as “prob­a­ble” or “pos­si­ble” car­cino­gens. This is be­cause it ig­nores the dosage, fail­ing to con­sider the like­li­hood of com­ing into con­tact with enough of the sub­stance to cause ac­tual harm. In the case of cof­fee, for ex­am­ple, one would need to drink more than 50 cups a day, for an ex­tended pe­riod of time, be­fore any dele­te­ri­ous ef­fects be­came likely.

Clas­si­fy­ing 2,4-D as a can­cer risk to hu­mans ig­nores ex­ten­sive re­search and anal­y­sis con­ducted by health author­i­ties world­wide, in­clud­ing the United Na­tions WHO/FAO Joint Meet­ing on Pes­ti­cide Residue (JMPR). This body eval­u­ates the risks of sub­stances like 2,4-D, con­sid­er­ing real-world vari­ables such as the amounts in soil and nearby wa­ter, ex­po­sure to an­i­mals pass­ing through treated fields, and the po­ten­tial for di­rect hu­man con­tact.

In re­views be­gin­ning in 1970, the JMPR has al­ways found that when 2,4-D is ap­plied cor­rectly, it does not pose a health threat to any­one or any­thing on land or wa­ter. This find­ing has been af­firmed by nu­mer­ous gov­ern­ment agen­cies, in­clud­ing the Euro­pean Food Safety Au­thor­ity, the EPA, the US Depart­ment of Agri­cul­ture, and Health Canada.

When the IARC, which re­stricts its pan­els to con­sider only a nar­row spec­trum of se­lected publi­ca­tions, makes a mis­taken de­ci­sion, the ef­fects are harm­ful. Its rul­ings give cred­i­bil­ity to chemo­pho­bic ac­tivists look­ing for head­lines and raise the like­li­hood that sub­stances wrongly la­beled as harm­ful will be re­placed by other prod­ucts that could pose greater risks or pro­vide fewer ben­e­fits.

If prod­ucts such as glyphosate and 2,4-D were to be­come un­avail­able, farm­ers would be forced to re­sort to other meth­ods to con­trol weeds – none of them as ef­fi­cient. In­deed, many of the al­ter­na­tives would be more toxic or re­quire more tillage, re­sult­ing in dam­ag­ing soil ero­sion, in­creased CO2 emis­sions, de­creased crop yields, greater pro­duc­tion costs, and higher con­sumer prices.

Nor would the prob­lem be lim­ited to farm­ers. There are more than 100 pre­scribed uses for 2,4-D, in­clud­ing the con­trol of in­va­sive weeds on lawns, in forestry, and to en­hance safety along highways, power line cor­ri­dors, and rail lines. The process the IARC uses in com­ing to con­clu­sions is not only sci­en­tif­i­cally wrong; it is harm­ful. Its de­ci­sions, which have wide ex­po­sure, pose the great­est risk to hu­man and other an­i­mal life – at any dose.

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