Question

One way to identify use of methamphetamine in a population is to monitor the waste water. Methamphetamine is excreted from the body up to 23% unchanged and can cause unintended environmental exposures. It has been detected in the sewage of all major cities, even after sewage treatment. Methamphetamine is organic base with a pKaof 10.0 [12].

a. Many sewage treatment facilities induce pH ranges from pH 5 to pH 10 to encourage degradation. Is methamphetamine charged at these extremes? Also, circle and name the functional group(s) predominately responsible for the pKa. Please provide your reasoning.

b. Methamphetamine is excreted in urine as a cation. Assuming it enters the environment as a cation, which of the four environmental compartments would you expect to find methamphetamine? Use chemical properties and environmental properties to justify your reasoning. (Hint: there are potentially two compartments.)

c. Assuming methamphetamine enters the environment as a cation through urine, what environmental properties determine which environmental compartment methamphetamine will be in?

d. Roughly three to six pounds of toxic waste is produced for each pound of

methamphetamine produced. Vapors created during production also cause further

environmental contamination, depositing the un-charged drug on surfaces near the

production site. The log Kow of methamphetamine is 2.07. What is the ratio of

methamphetamine in octanol:water?

i. What does this imply about BCF?

ii. What does it imply about K

d

?

iii. Also, what does all of this mean when we are talking about environmental

transport and potential persistence of methamphetamine in the environment?

Answer 1

(a) Methamphetamine ( N-methyl-1-phenylpropan-2-amine) is a organic compound which is used as central nervous system stimulants. It has been detected in sewage facilities of many cities, indicating massive use by human population. It is a base with Pka value of 10. This high value of Pka indicates its weaker tendency to dissociate a proton, contributed by the presence of Amine group. Presence of Methyl group prevents its degradation.

removal of the chemical from the sewage also depends upon the efficiency of sewage treatment facility used in the area.

(b) Methamphetamine affects these two main environmental compartments:

i- Water bodies (Hydrosphere)

ii- Air (Atmosphere)

As Methamphetamine is excreted in unaltered form through urine or faeces, its persistence in water bodies become evident. These drugs have a high potential to escape in the environment during intake in powder form or improper handling or via smoke during consumption.

(c) Persistence of Methamphetamine in the surrounding can be assessed by the changes associated with the chemical on the living components of the surrounding area.

(d) Kow (octanol- water partition co-efficient) is a very useful parameter to measure toxicity of drugs.It is the ratio of the concentration of chemical in the octanol form to the concentration in aqeuous form. As its log Kow is given as 2.07. Its octanol:water ratio is anti log (2.07).

(i) kow estimates the BCF (bio concentration factor) . the higher the log kow value, higher is the tendency to concentrate the chemical in the medium, thus increasing BCF value.

(ii) It shows its low dissociation constant (kd) leading to its more affinity to be present in bounded form.

(iii) Every chemical parameters mentioned above related to methamphetamine shows its great persistent in environment and slow degradation by bio-chemical processes.