| Course | PHLT 8034 Environmental Health |
|---|---|
| Week | Week 2 |
| Paper type | Discussion post |
| Length | About 570 words, 4 pages |
| Format | Discussion post, APA 7 citations |
| School | Walden University |
| Program | PhD in Public Health |
| Updated | October 2026 |
Free sample paper for PHLT 8034 Week 2
Week 2 Discussion: Initial Post
The Shower Before the Glass: Ranking Ingestion, Inhalation and Skin Contact as Routes of Trihalomethane Exposure From a Chlorinated Surface Water Supply
Initial Post
My agent this week is the family of trihalomethanes, chiefly chloroform, that forms when chlorine used for disinfection reacts with natural organic matter in source water. The setting is a composite town whose supply comes from a river reservoir, where organic matter rises after autumn leaf fall and summer algae growth, so byproduct formation varies through the year. Drinking water rules set limits on these compounds, and the town reports its running averages. My argument is about what happens after the water reaches the house: the glass of water most people picture may not be the main way residents take these compounds in.
There are three routes, and I set them side by side.
Ingestion is the familiar one. Residents drink tap water, cook with it and make coffee and formula with it, and the compounds pass through the gut. Boiling drives off some of the most volatile byproducts, so cooked water carries less than water drunk cold from the tap.
Inhalation happens mainly in the bathroom. Trihalomethanes are volatile, and hot water from a shower releases them into the small, warm, enclosed air of the bathroom, where they are breathed for as long as the shower runs and for some minutes afterward.
Skin absorption happens at the same time. Warm water on large areas of skin allows these small, fat-soluble molecules to cross into the body directly, and laboratory work on human skin has shown that chloroform penetrates far more readily than the nonvolatile haloacetic acids formed by the same disinfection process (Xu et al., 2002).
Here is the ranking I want to defend. For trihalomethanes, the two shower routes together can match or exceed drinking. The most direct evidence comes from a study that measured trihalomethanes in volunteers' blood before and after ordinary household activities: blood levels rose far more after a shower or bath than after drinking a liter of tap water (Backer et al., 2000). A case-control study of bladder cancer in Spain pointed the same way, finding that the association with byproduct exposure was stronger for showering, bathing and swimming than for drinking alone (Villanueva et al., 2007). Neither study establishes the exact share each route contributes, and I am not offering percentages. What they show is that a ranking with ingestion at the top does not fit these compounds.
The ranking depends on conditions. A short, cool shower in a ventilated bathroom shifts the balance back toward drinking. A household that drinks mostly bottled water shifts it further toward the shower. Bathtubs and pools change the picture again because of longer contact. And the ranking is specific to volatile byproducts. Haloacetic acids, also formed by chlorination, do not evaporate easily and penetrate skin poorly, so for them ingestion should dominate (Richardson et al., 2007).
This matters for public health practice. If the town issued a drinking water advisory telling residents to use a filter pitcher, the advice would address the route that may matter least for trihalomethanes. Reducing formation at the treatment plant, by removing organic matter before chlorination, acts on every route at once.
A question for classmates: for the agent you chose, does one route dominate so clearly that a ranking is obvious, or do the conditions of everyday use change the order the way they do for byproducts in shower water?
References
Backer, L. C., Ashley, D. L., Bonin, M. A., Cardinali, F. L., Kieszak, S. M., & Wooten, J. V. (2000). Household exposures to drinking water disinfection by-products: Whole blood trihalomethane levels. Journal of Exposure Analysis and Environmental Epidemiology, 10(4), 321-326. https://doi.org/10.1038/sj.jea.7500098
Richardson, S. D., Plewa, M. J., Wagner, E. D., Schoeny, R., & DeMarini, D. M. (2007). Occurrence, genotoxicity, and carcinogenicity of regulated and emerging disinfection by-products in drinking water: A review and roadmap for research. Mutation Research/Reviews in Mutation Research, 636(1-3), 178-242. https://doi.org/10.1016/j.mrrev.2007.09.001
Villanueva, C. M., Cantor, K. P., Grimalt, J. O., Malats, N., Silverman, D., Tardon, A., Garcia-Closas, R., Serra, C., Carrato, A., Castano-Vinyals, G., Marcos, R., Rothman, N., Real, F. X., Dosemeci, M., & Kogevinas, M. (2007). Bladder cancer and exposure to water disinfection by-products through ingestion, bathing, showering, and swimming in pools. American Journal of Epidemiology, 165(2), 148-156. https://doi.org/10.1093/aje/kwj364
Xu, X., Mariano, T. M., Laskin, J. D., & Weisel, C. P. (2002). Percutaneous absorption of trihalomethanes, haloacetic acids, and haloketones. Toxicology and Applied Pharmacology, 184(1), 19-26. https://doi.org/10.1006/taap.2002.9494
Reading the PHLT 8034 Week 2 instructions
The second thread usually asks students to take one agent and compare the routes by which people are exposed to it, then argue which matters most. Faculty expect more than a list of ingestion, inhalation and dermal contact: the analysis lies in ranking them and explaining why. Each study should be characterized by the quantity it actually measured, and relative contributions should never be invented to make a ranking look precise. Strong posts name the conditions under which the ranking would change, since route importance depends on behavior, building ventilation and the agent's chemistry. Many prompts also ask what the ranking means for prevention or advice. A source behind each major claim is expected, along with a closing question that invites classmates to examine the route their own agent depends on. Posts of five to seven hundred words are common.
How the PHLT 8034 Week 2 example is put together
An opening paragraph introduces trihalomethanes, explains how chlorine and organic matter form them, and places them in a reservoir town whose levels vary by season. Three short paragraphs describe the routes in parallel: drinking and cooking, breathing shower air, and absorption through warm skin, the last supported by laboratory work on skin penetration. The ranking paragraph cites a study that measured blood levels before and after household activities and a case-control study of bladder cancer, then states clearly that neither fixes each route's share. A paragraph on conditions explains how shower length, ventilation, bottled water, bathtubs and pools shift the balance, and why less volatile byproducts reverse it. A practice paragraph contrasts a filter advisory with treatment-plant control, and a final line asks peers whether the routes for their own agents compete the same way.
Where the marks sit in the PHLT 8034 Week 2 rubric
A ranking argued from evidence earns the analytic share; a list of routes earns little. Graders read closely how studies are characterized: describing what was measured, blood levels after showers or associations by type of water use, is rewarded, while attaching invented percentages to each route is penalized. The paragraph on conditions carries significant credit because recognizing when a ranking changes is the doctoral move in this thread. The connection to prevention, showing that the ranking changes which advice would help, demonstrates applied reasoning. Accuracy about chemistry matters too, since volatility explains why the ranking holds for these compounds and not for haloacetic acids. Citations should support specific claims, and the last line earns participation credit when it gets peers ranking routes for their own agents instead of merely naming them.
PHLT 8034 Week 2 help from the desk
Route posts often stop at naming the three routes. Push past that by committing to an order and defending it with studies that measured something relevant, then say when your order would change. Describe evidence by what it measured rather than borrowing numbers you cannot verify. Think about the agent's chemistry: volatility, solubility and skin penetration decide which routes compete. Connect the ranking to practice by asking which intervention would address the dominant route. End with a question that asks peers whether their agent's ranking is obvious or conditional. A ranked-route post can be drafted around whichever agent your instructor hands out.
Get a PHLT 8034 Week 2 example written to your instructions
Once the desk has the agent under discussion and the prompt and rubric, a post ranking its routes of entry, with two replies, is ready in 24-48h; a first one costs nothing. Exposure studies are described by what they measured, and no share of intake is given a number the literature did not publish.
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PHLT 8034 Week 2 questions, answered
Why trihalomethanes rather than lead or bacteria in water?
Because their volatility makes the route question genuinely contested. For lead in water, ingestion dominates so clearly that a ranking thread has little to argue; for trihalomethanes, inhalation and skin contact during bathing are serious competitors in the exposure literature. Any agent with at least two plausible routes works for this thread, and your section's assigned agent takes priority.
What if the studies disagree about the ranking?
Then the disagreement becomes part of the post. The sample notes that results shift with how people bathe and how bathrooms are ventilated, and that studies run under different conditions reach different balances between routes. Reporting that spread honestly, with the conditions named, reads as stronger reasoning than choosing the study that best supports a tidy conclusion.
Is a local water utility report acceptable as a source?
Yes, for what it is. Utility reports establish which byproducts are present and how they are monitored in that system, which supports the first half of the post. They say little about how people are exposed once the water is in the home, so the route argument leans on published exposure studies instead. The sample cites both kinds and keeps their roles separate.
Where can I find a free PHLT 8034 Week 2 sample paper?
This page holds the complete Week 2 post ranking ingestion, shower inhalation and skin contact for trihalomethanes in chlorinated water, with four references and a closing question.
Does this mean drinking water advisories are useless for byproducts?
Not useless, but incomplete for volatile compounds. Advice aimed only at drinking water leaves shower exposure untouched, while reducing byproduct formation at the treatment plant lowers exposure through every route.