DOI: 10.3886/icpsr38648.v1
title: Population Distribution and Factors Affecting Individual DNA Shedding Propensity, New York City, New York, 2019-2022
title: Version 1

description: This two-phase forensic science study examined how much DNA individuals carry on their skin surface. The main goal for phase 1 was the development of a standardized method to test for human DNA shedding propensity. Shedding propensity is defined as how much DNA a person leaves behind when touching a surface. In phase 1 the research team collected skin surface samples and fingerprints from different locations for 30 volunteers on three different occasions.
The main goal of phase 2 was to use the sampling location established in phase 1 to determine the distribution of different levels of individual shedding propensity in four U.S. ethnic groups and correlate DNA shedding to biological characteristics of these test populations. Biological characteristics (e.g., sunburn or sweating propensity) were collected via a questionnaire or measured via dermatological probes (e.g., sebum and melanin content).
description: This two-phase study attempted to answer the following research questions:
Are skin surfaces other than unwashed or washed hands representative of an individual's DNA shedding propensity?
Is shedding propensity correlated to biological factors such as age, gender, sunburn risk, or sweating propensity?
The main goal for phase 1 was the development of a standardized method to test for human DNA shedding propensity. Shedding propensity is defined as how much DNA an individual leaves behind when touching a surface. This "DNA shedding propensity" can become relevant if passive DNA transfer could explain a crime scene result.
Phase 1 had several sub-objectives. Objective 1 was to collect skin surface samples and fingerprints from different locations for 30 volunteers on three different occasions. Objective 2 was to extract, quantitate, and type DNA for all samples. Objective 3 was to interpret the resulting DNA data, analyze for reproducibility and correlations between sampling locations, and select the most suitable skin surface location for standardized collection in phase 2.
The main goal of phase 2 was to use the standardized collection and determine the distribution of different levels of individual shedding propensity in four U.S. ethnic groups, and correlate DNA shedding to biological and medical characteristics of these test populations.
Phase 2 also had multiple sub-objectives. Objective 1 was to use the standardized DNA collection location and collect samples from 100 volunteers. Objective 2 was to collect physical skin surface measurement and questionnaires from the 100 volunteers. As in phase 1, objective 3 for phase 2 was to extract, quantitate, and type DNA for all samples. Objective 4 was to collate the resulting skin surface, biological, and DNA data, and perform multivariate correlation testing for the data set.
description: For the first phase 30 adult volunteers returned on three separate days a week apart and each time donated a set of eight skin surface samples. The tested skin areas were: right and left thumb prior to hand washing, right and left combined digit and middle finger 30 minutes after hand washing, right toe, nape, neck below ear, and the inside of the upper arm. Volunteers also filled out a short questionnaire asking for information regarding gender, age, hand dominance, time since shower, and time since hand washing. Two samples had to be removed from phase 1. The final data analysis covered 13 female and 15 male donors (n=28).
For the second phase 103 volunteers donated skin surface samples from their fingertips after hand washing. Two samples (thumb and combined digit and middle finger) from the non-dominant hand were collected after 30 minutes without activity, equivalent samples from the non-dominant hand were collected after one hour of controlled activity on a DNA free tablet. All volunteers also donated a buccal swab as a DNA reference.
Phase 2 volunteers filled out a questionnaire covering the same phase 1 items, as well as information on ancestry, height, weight, sunburn and sweating propensity, and alcohol, nicotine, and medication use. Different skin locations were tested for sebum content, hydration, and melanin content using a C+K Multiprobe Set. A research assistant observed each volunteer for the 60-minute period and counted how often they touched either an exposed skin or clothed area. Three samples failed and were removed from phase 2. The final data analysis included 74 female and 26 male donors (n=100)
description: Not applicable
description: Response Rates: Phase 1 targeted 30 volunteers. Due to technical failures 28 were included in the DNA quantitation study and 24 in the cell count study. Phase 2 yielded 103 volunteers and a final sample number of 100.
description: Presence of Common Scales: None
description: Datasets: 
DS1: Population Distribution and Factors Affecting Individual DNA Shedding Propensity, New York City, New York, 2019-2022
description: Adult volunteers in New York City. Smallest Geographic Unit: None
description: coded on-site observation; on-site questionnaireThese data are a Fast Track Release and are distributed as they were received from the data producer. An Excel file has been zipped for release, but not checked or processed. Users should refer to the accompanying ICPSR README file for a brief description of the data available with this collection and consult with the investigator(s) if further information is needed.