Wednesday, March 12, 2008

Toxicity of Coffee versus common Lawn weed killers(2,4-D)

How do 2,4-D mixtures used to kill weeds on lawns compare in toxicity to coffee?

2,4-D is a common weed killer used in lawn care programs to keep dandelions and other weeds out of lawns. How toxic is this commonly used pesticide? Do you still want to drink coffee?

According to . . . “Although the United States hasn't yet developed guidelines for caffeine intake and kids, Canadian guidelines recommend that preschool children get no more than 45 milligrams of caffeine a day. That's equivalent to the average amount of caffeine found in a 12-ounce (355-milliliter) can of soda or four 1.5-ounce (43-gram) milk chocolate bars.” Or also the amount found in a cup of coffee.

From Wikipedia, we find that “The median lethal dose (LD50) of caffeine is 192 milligrams per kilogram in rats.” The wikipedia article also states that “In general, one serving of coffee ranges from 40 milligrams, for a single shot (30 milliliters) of arabica-variety espresso, to about 100 milligrams for a cup (120 milliliters) of drip coffee.

On the toxicity of 2,4-d, Wikipedia says “The LD50 . . . according to US EPA 2,4-D Reregistration Eligiblity Decision, 2006, is 639 mg/kg.” This means that the main herbicidal ingredient used in common lawn weed killer mixtures is 3 time LESS toxic than caffeine.

2,4-D is usually found in a mixture. If one were to use the LD50 of Killex a common retail product – the LD50 is listed as 375 mg/kg- which would make it only HALF as toxic as caffeine.

But what about the toxicity in its common form. For coffee- LD50 192 milligrams per kilogram with 40 milligrams per 120 milliliter cup. This calculates that a 1 kg rat would have to drink 192/40 = 4.8 cups of coffee to get the 192 milligrams of caffeine to provide a Lethal Dose to 50% of the population. At 120 ml per cup that would mean 576 millilitres of coffee.

According to, an average female weighs 162 pounds (=162/2.24= 72 kg). This means this average female would have to drink 4.8 cups times 72 kg or 561 cups of coffee to receive a lethal dose of caffeine.

How about 2,4-D is in a spray mixture? According to , the LD50 for the Killex mixture is >5000 mg/kg.

If Killex weighs similar to water, then 1 ml weighs 1 mg. Which means the poor rat would have to drink/ingest 5000 ml or 5 litres of Killex concentrate to receive a lethal dose.

Therefore compared to coffee, Killex concentrate is 5000/576 is 8 times less toxic than coffee.

Since Killex ( a common weed control mixture) is normally used in a mix the same rate would need a large volume of Killex mixture. The suggested rate is 5.5 Litres per hectare in 300-1,500 Litres. Using the most concentrated rate would mean 5.5 L/300 Litres or 5500 ml/300 litres or which equals 55ml/3 litres or 19 ml/litre Therefore to get 500 mg of Killex into that poor rat, he would need to ingest 5000/19 = 263 litres of Killex mixture.

In comparison, therefore the weed killer sprayed on lawns is 263 litres/.576 litres or 456 times LESS toxic than coffee. Weed killer spray is 456 times LESS toxic than Coffee.

Or Coffee is 456 time MORE TOXIC than weed killer.